Volume 19,Issue 5,2021 Table of Contents
2021, 19(5):833-842.
Abstract:
Urbanization can greatly change the underlying surface and thus have a large influence on the urban runoff process.Recently,most big cities in China have undergone serious waterlogging problems which are caused by many factors,such as the "July 21" urban flood in Beijing,the heavy rain in Wuhan on July 6,2016 and the "May 22" torrential rain in Guangzhou in 2020 all caused huge economic losses.Since 2013,China has promoted the construction of sponge cities to play the role of nature in regulating water bodies,reducing urban waterlogging and water pollution through a series of measures.Low impact development (LID) is considered as a useful practice for sponge city construction and can reduce urban surface runoff to a certain extent. To evaluate the influence of LID on urban runoff generation in sponge city construction,this work takes Guangming District of Shenzhen as the study area and analyzes the impact of different LID measures and their combinations on the urban rainwater process by establishing a regional SWMM model.After the verification by the observed rainfallrunoff,a reasonable and effective model is obtained to simulate the runoff process.The different return period of design rainfall (1 a,5 a,10 a,20 a,50 a,100 a) was input into the model,four LID layout schemes (green roof,permeable pavement,sunken green space,and combined layout) were designed,and three LID areas (10%,20%,30%) were laid into the model at the same time.Their simulated runoff results were compared with those of traditional NO-LID,respectively. The results show that the SWMM model constructed can well simulate the rainfall-runoff process in the study area,with Nash-Sutcliffe efficiency coefficient of 0.868 and relative error of 0.186.The greater the rainfall intensity is,the greater the peak value and flood amount of urban rainfall-runoff are under the design rainfall of different return periods,which indicates that the short-duration and high-intensity rainfall tends to form higher flood peak and flood amount of runoff,which is one of the causes of urban waterlogging.With the same rainfall intensity and LID type,it becomes more obvious for the reduction effect of LID measures on runoff with the increase of LID layout area.The impervious rate of urban underlying surface was changed by LID layout area,which could greatly affect the urban rainfallrunoff process.LID can reduce both the peak value and total amountof runoff,and delay the peak time to some extent.Besides,the larger the area of LID is,the more obvious the effect of LID on runoff reduction is.The combined layout scheme has a better regulation effect on runoff than the single layout scheme.While in the single layout scheme,the best runoff reduction effect is permeable pavement,the best peak runoff regulation effect is green roof,and the sunken green space has the worst runoff regulation effect among the three.Sponge measures on runoff coefficientand peak flow reduction effect is abate in designed rainfall with a return period of more than 10 years,meaning that the sponge measures reach saturation later,the urban waterlogging relief mainly reflected in the case of the small intensity of rainfall. Both the structure and area of the LID layout have an impact on urban rainfall and runoff,and the reasonable layout of LID can effectively alleviate urban waterlogging to a certain extent.The regulation effect of LID measures under low rainfall intensity is obvious,but its regulation effect quickly reaches saturation in view of heavy rain,and the regulation of urban rain and flood in sponge city is "elastic",so it is necessary to further optimize the layout scheme in view of heavy rain,such as considering the dynamic coordination of greygreen measures,increasing the saturation threshold of sponge measures,and grasping the whole from the perspective of urban ecosystem to realize the effective control and utilization of rainwater runoff.
Urbanization can greatly change the underlying surface and thus have a large influence on the urban runoff process.Recently,most big cities in China have undergone serious waterlogging problems which are caused by many factors,such as the "July 21" urban flood in Beijing,the heavy rain in Wuhan on July 6,2016 and the "May 22" torrential rain in Guangzhou in 2020 all caused huge economic losses.Since 2013,China has promoted the construction of sponge cities to play the role of nature in regulating water bodies,reducing urban waterlogging and water pollution through a series of measures.Low impact development (LID) is considered as a useful practice for sponge city construction and can reduce urban surface runoff to a certain extent. To evaluate the influence of LID on urban runoff generation in sponge city construction,this work takes Guangming District of Shenzhen as the study area and analyzes the impact of different LID measures and their combinations on the urban rainwater process by establishing a regional SWMM model.After the verification by the observed rainfallrunoff,a reasonable and effective model is obtained to simulate the runoff process.The different return period of design rainfall (1 a,5 a,10 a,20 a,50 a,100 a) was input into the model,four LID layout schemes (green roof,permeable pavement,sunken green space,and combined layout) were designed,and three LID areas (10%,20%,30%) were laid into the model at the same time.Their simulated runoff results were compared with those of traditional NO-LID,respectively. The results show that the SWMM model constructed can well simulate the rainfall-runoff process in the study area,with Nash-Sutcliffe efficiency coefficient of 0.868 and relative error of 0.186.The greater the rainfall intensity is,the greater the peak value and flood amount of urban rainfall-runoff are under the design rainfall of different return periods,which indicates that the short-duration and high-intensity rainfall tends to form higher flood peak and flood amount of runoff,which is one of the causes of urban waterlogging.With the same rainfall intensity and LID type,it becomes more obvious for the reduction effect of LID measures on runoff with the increase of LID layout area.The impervious rate of urban underlying surface was changed by LID layout area,which could greatly affect the urban rainfallrunoff process.LID can reduce both the peak value and total amountof runoff,and delay the peak time to some extent.Besides,the larger the area of LID is,the more obvious the effect of LID on runoff reduction is.The combined layout scheme has a better regulation effect on runoff than the single layout scheme.While in the single layout scheme,the best runoff reduction effect is permeable pavement,the best peak runoff regulation effect is green roof,and the sunken green space has the worst runoff regulation effect among the three.Sponge measures on runoff coefficientand peak flow reduction effect is abate in designed rainfall with a return period of more than 10 years,meaning that the sponge measures reach saturation later,the urban waterlogging relief mainly reflected in the case of the small intensity of rainfall. Both the structure and area of the LID layout have an impact on urban rainfall and runoff,and the reasonable layout of LID can effectively alleviate urban waterlogging to a certain extent.The regulation effect of LID measures under low rainfall intensity is obvious,but its regulation effect quickly reaches saturation in view of heavy rain,and the regulation of urban rain and flood in sponge city is "elastic",so it is necessary to further optimize the layout scheme in view of heavy rain,such as considering the dynamic coordination of greygreen measures,increasing the saturation threshold of sponge measures,and grasping the whole from the perspective of urban ecosystem to realize the effective control and utilization of rainwater runoff.
2021, 19(5):843-852.
Abstract:
As the climate warms,permafrost degradation becomes progressively serious in cold regions.The changing characteristics of the frozen depth of permafrost have become the focus of many hydrologists and ecologists,and also become the hot and difficult point of hydrology research in cold regions.It is of great significance to study the variation characteristics of permafrost in the source region of the Yellow River for understanding the rules of alpine hydrological science,exploring the regional ecohydrological process and building the ecological civilization in the cold region. Use of 9 weather stations data from 1997 to 2018 of daily temperature,surface temperature and frozen soil depth data,and using the linear trend analysis,inverse distance weighted interpolation method based on ArcGIS,elevation interpolation method and the correlation coefficient method,the temperature and seasonally frozen soil of Yellow River source area maximum freezing depth and start-stop time freeze cycle are analyzed.The relationship between maximum freezing depth and temperature was also studied. The distribution of the maximum freezing depth of seasonally frozen soil in the source region has obvious latitude zoning and vertical distribution,and the higher latitude area is greater than the lower latitude area,and the higher altitude area is greater than the lower altitude area.At the same time,compared with the regions with high latitude and high altitude,the freezing start date of frozen soil appears earlier,the thawing date appears later,and the freezing period is longer in the regions.The starting and ending time of seasonal permafrost in the source region has changed,which generally showed the starting time of freezing is later,the thawing time is earlier,and the freezing period is shorter.The variation range is different in different regions,and the average shortening rate in the source region is 8 d/(10 a). Interpretation: In recent 20 years,the temperature in most of the source area rise to a different extent,and maximum freezing depth showed a decrease trend of permafrost.The maximum frozen soil depth and winter average temperature geothermal ground temperature,average temperature cycle,the negative accumulated temperature is a negatively correlated relationship.It′s response to the negative accumulated temperature is the most significant,the correlation coefficient R=0.762 7.It shows that the maximum permafrost depth will decrease by 7.07 cm when the negative accumulated temperature rises by 100 ℃.
As the climate warms,permafrost degradation becomes progressively serious in cold regions.The changing characteristics of the frozen depth of permafrost have become the focus of many hydrologists and ecologists,and also become the hot and difficult point of hydrology research in cold regions.It is of great significance to study the variation characteristics of permafrost in the source region of the Yellow River for understanding the rules of alpine hydrological science,exploring the regional ecohydrological process and building the ecological civilization in the cold region. Use of 9 weather stations data from 1997 to 2018 of daily temperature,surface temperature and frozen soil depth data,and using the linear trend analysis,inverse distance weighted interpolation method based on ArcGIS,elevation interpolation method and the correlation coefficient method,the temperature and seasonally frozen soil of Yellow River source area maximum freezing depth and start-stop time freeze cycle are analyzed.The relationship between maximum freezing depth and temperature was also studied. The distribution of the maximum freezing depth of seasonally frozen soil in the source region has obvious latitude zoning and vertical distribution,and the higher latitude area is greater than the lower latitude area,and the higher altitude area is greater than the lower altitude area.At the same time,compared with the regions with high latitude and high altitude,the freezing start date of frozen soil appears earlier,the thawing date appears later,and the freezing period is longer in the regions.The starting and ending time of seasonal permafrost in the source region has changed,which generally showed the starting time of freezing is later,the thawing time is earlier,and the freezing period is shorter.The variation range is different in different regions,and the average shortening rate in the source region is 8 d/(10 a). Interpretation: In recent 20 years,the temperature in most of the source area rise to a different extent,and maximum freezing depth showed a decrease trend of permafrost.The maximum frozen soil depth and winter average temperature geothermal ground temperature,average temperature cycle,the negative accumulated temperature is a negatively correlated relationship.It′s response to the negative accumulated temperature is the most significant,the correlation coefficient R=0.762 7.It shows that the maximum permafrost depth will decrease by 7.07 cm when the negative accumulated temperature rises by 100 ℃.
2021, 19(5):853-861.
Abstract:
Water scarcity has become a common global problem.As a mega-city,Beijing supports more than 20 million permanent residents with 2.16 billion m3 of local water resources.South-to-North Water Diversion and recycled water could resolve the crisis of water resource shortage of Beijing effectively,while virtual water flow with commodity trade has also changed the distribution of water resources in economic sectors and regions,and played an important role in alleviating water shortages.To fully reflect water resources bearing capacity,it is required to analyze the virtual water consumption and trade from the perspective of industrial structure and commodity trade. An urban virtual water accounting framework is proposed based on input-output table and the direct and complete water consumption coefficients of the 8 major departments of Beijing in 2007,2012 and 2017 are analyzed under the background of industrial structure adjustment and watersaving work,as well as research the characteristics of sectoral virtual water consumption and virtual water flows among different sectors. From 2007 to 2017,the direct water use coefficient of all sectors in Beijing shows a downward trend,the direct and complete water use coefficient of agriculture are largest,and completer water use coefficient drops from 716 m3/￥1 000 in 2007 to 222.1 m3/￥1 000 in 2017,the multiplier for agricultural water use declines from 1.6 to 1.2 which indicates the impact of agricultural development has weakened the increase in water use in other sectors.The direct water use coefficient of transportation,construction,and manufacturing sectors are small,but the water multiplier is large,and the increase in unit products of these will bring about water consumption in other sectors.In the past 10 years,the total local end use of virtual water has dropped from 5.37 billion m3 to 4.5 billion m3,the virtual water consumption in the service industry accounts for total virtual water consumption decreases from 32.8% to 30%,and the proportion of agriculture rises from 21% to 39%.As a net imputer of virtual water,the net virtual water imports of Beijing increases from 2.88 billion m3 to 2.98 billion m3 which accounts for more than 50 %of the final demand.Although agriculture consumes the most virtual water,it mainly relies on imputs from other provinces to meet the needs of Beijing.A comparative analysis of virtual water flows between 8 sectors in 2007 and 2017,it is found that the virtual water flow pattern remains unchanged,agriculture,mining,and water supply are the virtual water output sectors while construction,transportation,and service are the virtual water imput sectors.The net output of virtual water from agriculture is 982 million m3 in 2017,and the flow to manufacturing and service is 640 and 230 million m3,respectively.There are obvious outflow-inflow pairs，includig agriculture-manufacturing,agriculture-service,manufacturing-construction,manufacturing-service,manufacturing-transportation,and service-construction. With the advancement of water saving work and the improvement of water use efficiency,the direct water use coefficient of various departments has decreased,and virtual water consumption of Beijing has declined 14% in the past 10 years.The pressure on water resources could be relieved to some extent due to imput agriculture and mining with high water consumption and output service industry with low water consumption.In the future,watersaving work in Beijing will not only control the scale of water consumption in agriculture with large direct water use coefficients but also need to pay attention to the implementation of water-saving measures in the transportation,construction,manufacturing,electrical supply,and service industries.At the same time,it′s necessary to strengthen the management of water resources at end-users and reduce waste of products.
Water scarcity has become a common global problem.As a mega-city,Beijing supports more than 20 million permanent residents with 2.16 billion m3 of local water resources.South-to-North Water Diversion and recycled water could resolve the crisis of water resource shortage of Beijing effectively,while virtual water flow with commodity trade has also changed the distribution of water resources in economic sectors and regions,and played an important role in alleviating water shortages.To fully reflect water resources bearing capacity,it is required to analyze the virtual water consumption and trade from the perspective of industrial structure and commodity trade. An urban virtual water accounting framework is proposed based on input-output table and the direct and complete water consumption coefficients of the 8 major departments of Beijing in 2007,2012 and 2017 are analyzed under the background of industrial structure adjustment and watersaving work,as well as research the characteristics of sectoral virtual water consumption and virtual water flows among different sectors. From 2007 to 2017,the direct water use coefficient of all sectors in Beijing shows a downward trend,the direct and complete water use coefficient of agriculture are largest,and completer water use coefficient drops from 716 m3/￥1 000 in 2007 to 222.1 m3/￥1 000 in 2017,the multiplier for agricultural water use declines from 1.6 to 1.2 which indicates the impact of agricultural development has weakened the increase in water use in other sectors.The direct water use coefficient of transportation,construction,and manufacturing sectors are small,but the water multiplier is large,and the increase in unit products of these will bring about water consumption in other sectors.In the past 10 years,the total local end use of virtual water has dropped from 5.37 billion m3 to 4.5 billion m3,the virtual water consumption in the service industry accounts for total virtual water consumption decreases from 32.8% to 30%,and the proportion of agriculture rises from 21% to 39%.As a net imputer of virtual water,the net virtual water imports of Beijing increases from 2.88 billion m3 to 2.98 billion m3 which accounts for more than 50 %of the final demand.Although agriculture consumes the most virtual water,it mainly relies on imputs from other provinces to meet the needs of Beijing.A comparative analysis of virtual water flows between 8 sectors in 2007 and 2017,it is found that the virtual water flow pattern remains unchanged,agriculture,mining,and water supply are the virtual water output sectors while construction,transportation,and service are the virtual water imput sectors.The net output of virtual water from agriculture is 982 million m3 in 2017,and the flow to manufacturing and service is 640 and 230 million m3,respectively.There are obvious outflow-inflow pairs，includig agriculture-manufacturing,agriculture-service,manufacturing-construction,manufacturing-service,manufacturing-transportation,and service-construction. With the advancement of water saving work and the improvement of water use efficiency,the direct water use coefficient of various departments has decreased,and virtual water consumption of Beijing has declined 14% in the past 10 years.The pressure on water resources could be relieved to some extent due to imput agriculture and mining with high water consumption and output service industry with low water consumption.In the future,watersaving work in Beijing will not only control the scale of water consumption in agriculture with large direct water use coefficients but also need to pay attention to the implementation of water-saving measures in the transportation,construction,manufacturing,electrical supply,and service industries.At the same time,it′s necessary to strengthen the management of water resources at end-users and reduce waste of products.
2021, 19(5):862-873.
Abstract:
Accurate acquisition of precipitation data is very important for regional meteorological,hydrological,and water resources research.Precipitation data from meteorological stations are highly accurate,but the application of measured precipitation data is limited due to the uneven spatial distribution of stations.With the rapid development of satellite remote sensing technology,a large number of precipitation inversion products have developed.Precipitation products represented by TRMM are widely used in the fields of meteorology and water conservancy due to their high temporal and spatial resolution.Although remote sensing inversion precipitation products can effectively restore regional precipitation characteristics,there is still a problem of insufficient spatial resolution for refined water cycle simulation research. Taking the Luanhe River basin (LRB) as the research area,the applicability of the Global Precipitation Measurement Mission of 2018 was evaluated.Under the assumption of the unity of the relationship between data of different resolutions in the model simulation and based on the correlation between precipitation and impact factors that are elevation,latitude,longitude,and normalized difference vegetation index (NDVI),a product space downscaling model of GPM precipitation based on PSO-BP (particle swarm optimization-back propagation) was built.GPM precipitation products with a spatial resolution of 1 km in the LRB were obtained. In the evaluation of the applicability of GPM precipitation products,the correlation is only 0.59 at the annual scale.The correlation is the highest in spring and the lowest in summer at the seasonal scale.The root mean square error is the highest in summer and smaller in other seasons.The relative deviation values were greater than 0 on all time scales except spring.On the monthly scale,the correlation was greater than 0.6 in 9 months and reached more than 0.9 in April,May,and December.As June to September is the rainy season in the Luanhe River basin,the root mean square error was higher in July and August.The relative deviations were greater than 0 in all months except January,March,and April.Through analyzing original GPM and downscaling of GPM precipitation at different time scales,the correlation between the downscaling of GPM spatial data and the measured precipitation data increased to more than 0.85 at the annual and seasonal scales.The relative deviation values were close to 0 on all scales except winter.Compared with the precipitation measured by original GPM and downscaling GPM,the monthly correlation mean value increased by 0.25 and achieved above 0.8.The mean monthly root mean square error was reduced by 0.16 and the relative error was controlled within ±10%. The original GPM precipitation product can accurately express the precipitation in the LRB.However,there is a phenomenon of overestimation of precipitation and this is especially obvious in winter.At different time scales,the spatial downscaling of GPM precipitation based on the PSO-BP model has a higher correlation with the measured precipitation at the station.The root mean square error and relative deviation were smaller.This indicated that the GPM precipitation product obtained by the spatial downscaling method established could more accurately express the spatial distribution characteristics of precipitation in the LRB with higher accuracy.
Accurate acquisition of precipitation data is very important for regional meteorological,hydrological,and water resources research.Precipitation data from meteorological stations are highly accurate,but the application of measured precipitation data is limited due to the uneven spatial distribution of stations.With the rapid development of satellite remote sensing technology,a large number of precipitation inversion products have developed.Precipitation products represented by TRMM are widely used in the fields of meteorology and water conservancy due to their high temporal and spatial resolution.Although remote sensing inversion precipitation products can effectively restore regional precipitation characteristics,there is still a problem of insufficient spatial resolution for refined water cycle simulation research. Taking the Luanhe River basin (LRB) as the research area,the applicability of the Global Precipitation Measurement Mission of 2018 was evaluated.Under the assumption of the unity of the relationship between data of different resolutions in the model simulation and based on the correlation between precipitation and impact factors that are elevation,latitude,longitude,and normalized difference vegetation index (NDVI),a product space downscaling model of GPM precipitation based on PSO-BP (particle swarm optimization-back propagation) was built.GPM precipitation products with a spatial resolution of 1 km in the LRB were obtained. In the evaluation of the applicability of GPM precipitation products,the correlation is only 0.59 at the annual scale.The correlation is the highest in spring and the lowest in summer at the seasonal scale.The root mean square error is the highest in summer and smaller in other seasons.The relative deviation values were greater than 0 on all time scales except spring.On the monthly scale,the correlation was greater than 0.6 in 9 months and reached more than 0.9 in April,May,and December.As June to September is the rainy season in the Luanhe River basin,the root mean square error was higher in July and August.The relative deviations were greater than 0 in all months except January,March,and April.Through analyzing original GPM and downscaling of GPM precipitation at different time scales,the correlation between the downscaling of GPM spatial data and the measured precipitation data increased to more than 0.85 at the annual and seasonal scales.The relative deviation values were close to 0 on all scales except winter.Compared with the precipitation measured by original GPM and downscaling GPM,the monthly correlation mean value increased by 0.25 and achieved above 0.8.The mean monthly root mean square error was reduced by 0.16 and the relative error was controlled within ±10%. The original GPM precipitation product can accurately express the precipitation in the LRB.However,there is a phenomenon of overestimation of precipitation and this is especially obvious in winter.At different time scales,the spatial downscaling of GPM precipitation based on the PSO-BP model has a higher correlation with the measured precipitation at the station.The root mean square error and relative deviation were smaller.This indicated that the GPM precipitation product obtained by the spatial downscaling method established could more accurately express the spatial distribution characteristics of precipitation in the LRB with higher accuracy.
2021, 19(5):874-882.
Abstract:
Groundwater is significant for an important political,economic and cultural center (Beijing-Tianjin-Hebei) in China.Therefore,scientifically analyzing the spatiotemporal pattern of groundwater storage is fundamental research in the Beijing-Tianjin-Hebei region.However,there are some shortcomings in previous research,such as the limited locations of groundwater wells and the representation of in-situ data in a single geological condition.In the 21st century,the emerging GRACE satellite data,which is subject to little geological conditions,is applied in measuring water storage spatial continuity. Herein,the GRACE-based terrestrial water storage anomalies and global land data assimilation system(GLDAS) are used to retrieve the groundwater storage in the Beijing-Tianjin-Hebei region,and Sen′s slope and Mann-Kendall time series test are applied to analyze the spatiotemporal variations of groundwater. It is foand that the changing rate of groundwater is about -51.77 mm/a equivalent height of water in the Beijing-Tianjin-Hebei region from 2003 to 2019.Zonal statistics analysis with provincial administrative units showed that the depletion of groundwater in Beijing city has a minimum rate of -38.15 mm/a.Tianjin city has a maximum rate of -62.85 mm/a,and in Hebei Province,the rate of change is equivalent to the regional average rate of change with about -52.42 mm/a.The annual average groundwater storage of the National Bureau of Statistics was used to evaluate the GRACE-based retrieval result.It is also find that the groundwater storage has decreased about 375 million cubic meters from 2003 to 2019 in the entire region.Furthermore,the depletion of groundwater is significant in the western,southwestern,and central regions,but the depletion of groundwater is slight.In addition,the change of groundwater storage has some seasonal trend based on time-series analysis,the reduction of groundwater storage in summer is more than that in other seasons,with a mean rate of -75.99 mm/a,while the rate is the smallest in winter with about -37.24 mm/a equivalent height of water.The rate of change is similar in spring and autumn with a value of about -52.34 mm/a and -48.21 mm/a equivalent height of the water,respectively.According to the analysis of the change of groundwater storage in the same month of each year,it is found that the change value of groundwater storage fluctuated within a relatively stable range in the 12 months of the years,and the change value was generally low in June and July.The minimum in August,while December,January,and February are generally higher than that in other months,and the fluctuation range of the change is also smaller than that in other months.There are six months (March,April,May,September,October,November) when the distribution range and fluctuation range of the changes in groundwater storage are similar.When analyzing the impact factors,the groundwater storage is negatively correlated with the area changes of forest land,construction land,and agricultural land,with the highest correlation coefficient of -0.65.While groundwater storage and grassland shrubs are positively correlated (correlation coefficient is 0.68,significant 0.004).Based on the analysis combining with precipitation data,it is found that anthropogenic factor has a greater impact on the groundwater storage than natural meteorological factor. The results are roughly the same as the statistical data of the Water Resources Bulletin,which both show that groundwater storage has decreased.Combining groundwater retrieval results with land use data,population data,precipitation data,and other auxiliary data,the spatiotemporal analysis methods are applied to analyze the spatiotemporal evolution pattern of groundwater,and it is concluded that the changing rate of groundwater storage of Beijing-Tianjin-Hebei is about -51.77 mm/a equivalentheight of water,and the lowest rate of change about -38.15 mm/a in Beijing city and the highest rate of change about -62.85 mm/ain Tianjin city.The rate of change in Hebei Province is about -52.42 mm/a,which is equivalent to that of regional average change.Based on the Sen′s slope and Mann-Kendall analysis,groundwater storage has a significant,negative trend in the western,southwestern,and central regions,and the minimum trend of depletion is present in the northeast.Time-series analysis showed that the changes in groundwater storage are seasonal and the impact factor analysis shown that the changes in groundwater storage in Beijing-Tianjin-Hebei are negatively correlated with area changes of forest land,construction land,and agricultural land,with the highest correlation coefficient value of -0.65.While the groundwater storage and grassland shrubs are positively correlated (the correlation coefficient is 0.68,the significance is 0.004).Based on the analysis combining with precipitation data,it is found that anthropogenic factor has a significant impact on the groundwater storage of Beijing-Tianjin-Hebei than natural meteorological factor.The research has a significance for protecting water safety and the ecological environment of the Beijing-Tianjin-Hebei region.
Groundwater is significant for an important political,economic and cultural center (Beijing-Tianjin-Hebei) in China.Therefore,scientifically analyzing the spatiotemporal pattern of groundwater storage is fundamental research in the Beijing-Tianjin-Hebei region.However,there are some shortcomings in previous research,such as the limited locations of groundwater wells and the representation of in-situ data in a single geological condition.In the 21st century,the emerging GRACE satellite data,which is subject to little geological conditions,is applied in measuring water storage spatial continuity. Herein,the GRACE-based terrestrial water storage anomalies and global land data assimilation system(GLDAS) are used to retrieve the groundwater storage in the Beijing-Tianjin-Hebei region,and Sen′s slope and Mann-Kendall time series test are applied to analyze the spatiotemporal variations of groundwater. It is foand that the changing rate of groundwater is about -51.77 mm/a equivalent height of water in the Beijing-Tianjin-Hebei region from 2003 to 2019.Zonal statistics analysis with provincial administrative units showed that the depletion of groundwater in Beijing city has a minimum rate of -38.15 mm/a.Tianjin city has a maximum rate of -62.85 mm/a,and in Hebei Province,the rate of change is equivalent to the regional average rate of change with about -52.42 mm/a.The annual average groundwater storage of the National Bureau of Statistics was used to evaluate the GRACE-based retrieval result.It is also find that the groundwater storage has decreased about 375 million cubic meters from 2003 to 2019 in the entire region.Furthermore,the depletion of groundwater is significant in the western,southwestern,and central regions,but the depletion of groundwater is slight.In addition,the change of groundwater storage has some seasonal trend based on time-series analysis,the reduction of groundwater storage in summer is more than that in other seasons,with a mean rate of -75.99 mm/a,while the rate is the smallest in winter with about -37.24 mm/a equivalent height of water.The rate of change is similar in spring and autumn with a value of about -52.34 mm/a and -48.21 mm/a equivalent height of the water,respectively.According to the analysis of the change of groundwater storage in the same month of each year,it is found that the change value of groundwater storage fluctuated within a relatively stable range in the 12 months of the years,and the change value was generally low in June and July.The minimum in August,while December,January,and February are generally higher than that in other months,and the fluctuation range of the change is also smaller than that in other months.There are six months (March,April,May,September,October,November) when the distribution range and fluctuation range of the changes in groundwater storage are similar.When analyzing the impact factors,the groundwater storage is negatively correlated with the area changes of forest land,construction land,and agricultural land,with the highest correlation coefficient of -0.65.While groundwater storage and grassland shrubs are positively correlated (correlation coefficient is 0.68,significant 0.004).Based on the analysis combining with precipitation data,it is found that anthropogenic factor has a greater impact on the groundwater storage than natural meteorological factor. The results are roughly the same as the statistical data of the Water Resources Bulletin,which both show that groundwater storage has decreased.Combining groundwater retrieval results with land use data,population data,precipitation data,and other auxiliary data,the spatiotemporal analysis methods are applied to analyze the spatiotemporal evolution pattern of groundwater,and it is concluded that the changing rate of groundwater storage of Beijing-Tianjin-Hebei is about -51.77 mm/a equivalentheight of water,and the lowest rate of change about -38.15 mm/a in Beijing city and the highest rate of change about -62.85 mm/ain Tianjin city.The rate of change in Hebei Province is about -52.42 mm/a,which is equivalent to that of regional average change.Based on the Sen′s slope and Mann-Kendall analysis,groundwater storage has a significant,negative trend in the western,southwestern,and central regions,and the minimum trend of depletion is present in the northeast.Time-series analysis showed that the changes in groundwater storage are seasonal and the impact factor analysis shown that the changes in groundwater storage in Beijing-Tianjin-Hebei are negatively correlated with area changes of forest land,construction land,and agricultural land,with the highest correlation coefficient value of -0.65.While the groundwater storage and grassland shrubs are positively correlated (the correlation coefficient is 0.68,the significance is 0.004).Based on the analysis combining with precipitation data,it is found that anthropogenic factor has a significant impact on the groundwater storage of Beijing-Tianjin-Hebei than natural meteorological factor.The research has a significance for protecting water safety and the ecological environment of the Beijing-Tianjin-Hebei region.
2021, 19(5):883-893.
Abstract:
In recent years,scholars have focused on the impact of groundwater recharge,development potential,conversion of surface and groundwater,and spring water supply,while less attention has been paid to regional groundwater dynamics and their causes.Jinan is a resource-based water-deficient city.The unreasonable exploitation of groundwater has resulted in no "spring" in the spring city and no "water" in the river.Therefore,scientific and reasonable planning and utilization of groundwater resources are important. Based on the groundwater level data from 1997 to 2016 in the downtown of Jinan city and evidence collection through field investigation,the interannual variation characteristics of the groundwater depth are analyaed with a statistical calculation of the average groundwater depth over the years and months.In ArcGIS software,the groundwater depth change contour map is drawn according to the monitoring data of each groundwater monitoring well,and the spatial distribution characteristics of the groundwater depth change rate are calculated and analyzed,and the dynamic change law of the groundwater depth and its influencing factors are explored based on the principle of water balance. The dynamics of groundwater depth during the year show a "single peak and single valley" phenomenon,reaching the maximum groundwater depth in the year from May to June,and reaching the minimum depth of the year from September to October.In the past 20 years,the groundwater depth has shown a steady downward trend.The average groundwater depth in urban areas has dropped by 2.527 m,and the average declining rate during the past 20 years was 0.133 m/a.The spatial changes of groundwater depth declining rate are characterized by the attenuation from the northeast to the southwest.After 2003,the amount of groundwater extraction decreased by about 300 million m3/a,and the urban groundwater storage variable changed from a negative equilibrium (-270 million m3/a) before 2003 to a positive equilibrium after 2003 (80 million m3/a). In the past 20 years,the groundwater depth in the urban area of Jinan has shown a steady downward trend.The average groundwater depth in urban areas has dropped by 2.527 m,and the average declining rate during the past 20 years was 0.133 m/a.After large-scale water-saving and springpreserving measures in 2003,groundwater extraction was decreased by about 300 million m3/a,and the urban groundwater storage variable in the downtown of Jinan city has changed from a negative equilibrium (-270 million m3/a) to a positive equilibrium (80 million m3/a).The decrease rate of groundwater depth in the urban area shows an overall reduction trend from northeast to southwest,and the response degree of groundwater depth in each district to groundwater extraction or recharge is different.Among them,Lixia district is located in the groundwater recharging area and is most sensitive to the recharging or mining of groundwater,while the Tianqiao district showed the most insensitive.The dynamic change of underground groundwater depth in the urban area is directly related to precipitation replenishment and artificial mining.In dry years,the buried depth of groundwater showed an obvious increasing trend,and it responded strongly to changes in precipitation.The dynamic distribution of the buried depth of groundwater showed obvious seasonal characteristics of "single peak and single valley".The change was rough as follows: Affected by spring irrigation,the largest buried depth of groundwater in the year is about May-June;affected by more precipitation during the flood season from July to September,the minimum water depth of the year generally appears in SeptemberOctober.
In recent years,scholars have focused on the impact of groundwater recharge,development potential,conversion of surface and groundwater,and spring water supply,while less attention has been paid to regional groundwater dynamics and their causes.Jinan is a resource-based water-deficient city.The unreasonable exploitation of groundwater has resulted in no "spring" in the spring city and no "water" in the river.Therefore,scientific and reasonable planning and utilization of groundwater resources are important. Based on the groundwater level data from 1997 to 2016 in the downtown of Jinan city and evidence collection through field investigation,the interannual variation characteristics of the groundwater depth are analyaed with a statistical calculation of the average groundwater depth over the years and months.In ArcGIS software,the groundwater depth change contour map is drawn according to the monitoring data of each groundwater monitoring well,and the spatial distribution characteristics of the groundwater depth change rate are calculated and analyzed,and the dynamic change law of the groundwater depth and its influencing factors are explored based on the principle of water balance. The dynamics of groundwater depth during the year show a "single peak and single valley" phenomenon,reaching the maximum groundwater depth in the year from May to June,and reaching the minimum depth of the year from September to October.In the past 20 years,the groundwater depth has shown a steady downward trend.The average groundwater depth in urban areas has dropped by 2.527 m,and the average declining rate during the past 20 years was 0.133 m/a.The spatial changes of groundwater depth declining rate are characterized by the attenuation from the northeast to the southwest.After 2003,the amount of groundwater extraction decreased by about 300 million m3/a,and the urban groundwater storage variable changed from a negative equilibrium (-270 million m3/a) before 2003 to a positive equilibrium after 2003 (80 million m3/a). In the past 20 years,the groundwater depth in the urban area of Jinan has shown a steady downward trend.The average groundwater depth in urban areas has dropped by 2.527 m,and the average declining rate during the past 20 years was 0.133 m/a.After large-scale water-saving and springpreserving measures in 2003,groundwater extraction was decreased by about 300 million m3/a,and the urban groundwater storage variable in the downtown of Jinan city has changed from a negative equilibrium (-270 million m3/a) to a positive equilibrium (80 million m3/a).The decrease rate of groundwater depth in the urban area shows an overall reduction trend from northeast to southwest,and the response degree of groundwater depth in each district to groundwater extraction or recharge is different.Among them,Lixia district is located in the groundwater recharging area and is most sensitive to the recharging or mining of groundwater,while the Tianqiao district showed the most insensitive.The dynamic change of underground groundwater depth in the urban area is directly related to precipitation replenishment and artificial mining.In dry years,the buried depth of groundwater showed an obvious increasing trend,and it responded strongly to changes in precipitation.The dynamic distribution of the buried depth of groundwater showed obvious seasonal characteristics of "single peak and single valley".The change was rough as follows: Affected by spring irrigation,the largest buried depth of groundwater in the year is about May-June;affected by more precipitation during the flood season from July to September,the minimum water depth of the year generally appears in SeptemberOctober.
2021, 19(5):894-899,929.
Abstract:
Hydrologic system is a high complexity and nonlinearity system,which exhibits great temporal and spatial variations.Deterministic and stochastic are the two broad methods that have been applied to modeling hydrological processes.The former approach considered the cyclic and periodic nature of hydrological processes,whereas the latter approach considered the complexity and irregularity.Both the deterministic and stochastic components are present in the hydrological system and intertwine to affect the variation of hydrological processes.Chaos theory can provide a bridge between deterministic and stochastic methods to investigate the inherent stochasticity of deterministic systems.It is recognized that simple deterministic systems are capable of generating a complex randomlike phenomenon due to the nonlinear action within the system.Recently,many applications of chaos theory to hydrology have been reported and yielded fruitful outcomes.However,there is enough research on chaotic characteristic identification,while the studies on chaotic prediction need to be further improved and expanded.Longterm hydrological prediction has always been a crucial issue in hydrology with several challenges and impediments.Due to the nonlinear and chaotic characteristics of the hydrologic process,it is difficult to make accurate forecasting,especially for prediction with longer lead time at monthly or yearly scale. The similarity model of phase space is a classical prediction approach based on chaos theory.The prediction approach was improred by proposing a quantitative type coupled similarity identification technique.The degree of spatial proximity between two phase points is defined as the "quantity" similarity by the Euclidean distance criterion,while the similarity degree of internal structure between two phase points is defined as the "type" similarity by the accumulated unit-step function.Moreover,a two-objective optimization model based on the quantity-type similarity was established for hydrological prediction within the chaos theory framework and then solved by the tolerant algorithm of stratified sequence.An example was illustrated for the future 12-month rainfall predictions. Both the original model and improved model were applied to the Danjiangkou reservoir basin for monthly rainfall prediction.The monthly rainfall in 2016 was predicted based on the monthly rainfall data set from 1981 to 2015.The chaotic characteristics were identified and the related parameters (time delay and embedded dimension) were determined by the autoregressive function and G-P algorithm.The similar phase points were selected by the euclidean distance (quantity similarity) in the original model by the coupled "quantity" and "type" similarity in the improved model.For the original model,6 months showed the absolute of the relative errors less than 25%.For the improved model,8 months yielded the absolute of the relative errors less than 25%.Compared to the original model,the annual average of absolute values of relative error in monthly rainfall prediction was reduced from 44% to 23%.In contrary to the original model,the correlation coefficient R was lifted from 0.74 to 0.93.Overall,the improved model had better performance for predicting monthly rainfall in most months. In conclusion,the"quantitative"-"type" similarity predictive model based on chaos theory is effective and feasible,providing a new way for monthly rainfall prediction.The coupled "quantity-pattern" similarity model was proposed for long-term prediction,and the concept of the model is applicable to hydrological time series forecasting with different lead time scales.
Hydrologic system is a high complexity and nonlinearity system,which exhibits great temporal and spatial variations.Deterministic and stochastic are the two broad methods that have been applied to modeling hydrological processes.The former approach considered the cyclic and periodic nature of hydrological processes,whereas the latter approach considered the complexity and irregularity.Both the deterministic and stochastic components are present in the hydrological system and intertwine to affect the variation of hydrological processes.Chaos theory can provide a bridge between deterministic and stochastic methods to investigate the inherent stochasticity of deterministic systems.It is recognized that simple deterministic systems are capable of generating a complex randomlike phenomenon due to the nonlinear action within the system.Recently,many applications of chaos theory to hydrology have been reported and yielded fruitful outcomes.However,there is enough research on chaotic characteristic identification,while the studies on chaotic prediction need to be further improved and expanded.Longterm hydrological prediction has always been a crucial issue in hydrology with several challenges and impediments.Due to the nonlinear and chaotic characteristics of the hydrologic process,it is difficult to make accurate forecasting,especially for prediction with longer lead time at monthly or yearly scale. The similarity model of phase space is a classical prediction approach based on chaos theory.The prediction approach was improred by proposing a quantitative type coupled similarity identification technique.The degree of spatial proximity between two phase points is defined as the "quantity" similarity by the Euclidean distance criterion,while the similarity degree of internal structure between two phase points is defined as the "type" similarity by the accumulated unit-step function.Moreover,a two-objective optimization model based on the quantity-type similarity was established for hydrological prediction within the chaos theory framework and then solved by the tolerant algorithm of stratified sequence.An example was illustrated for the future 12-month rainfall predictions. Both the original model and improved model were applied to the Danjiangkou reservoir basin for monthly rainfall prediction.The monthly rainfall in 2016 was predicted based on the monthly rainfall data set from 1981 to 2015.The chaotic characteristics were identified and the related parameters (time delay and embedded dimension) were determined by the autoregressive function and G-P algorithm.The similar phase points were selected by the euclidean distance (quantity similarity) in the original model by the coupled "quantity" and "type" similarity in the improved model.For the original model,6 months showed the absolute of the relative errors less than 25%.For the improved model,8 months yielded the absolute of the relative errors less than 25%.Compared to the original model,the annual average of absolute values of relative error in monthly rainfall prediction was reduced from 44% to 23%.In contrary to the original model,the correlation coefficient R was lifted from 0.74 to 0.93.Overall,the improved model had better performance for predicting monthly rainfall in most months. In conclusion,the"quantitative"-"type" similarity predictive model based on chaos theory is effective and feasible,providing a new way for monthly rainfall prediction.The coupled "quantity-pattern" similarity model was proposed for long-term prediction,and the concept of the model is applicable to hydrological time series forecasting with different lead time scales.
2021, 19(5):900-909.
Abstract:
Hebei low plain (HLP) is one of the most important grain production bases in China.But,it is facing a shortage of freshwater resources problem from a long time.Ponds are important facilities for regulating and storing rainwater and flood resources in HLP area,and the utilization of pond water has attracted increasingly attention.With the continuous development in remote sensing technology,it is frequently applied to extract and analyse the water bodies such as ponds and wetlands,and it is main research means to study the temporal and spatial changes of pond water.However,there are few comprehensive studies on the quantity and quality of pond water at present.For HLP,the utilization value of unconventional pond water remains to be further studied. Cangzhou was taleen as a typical area of HLP.The quantity of the pond water in May and October of 1990,2000,2010,and 2019 in Cangzhou city were analyzed by the remote sensing technology,and the pond water was extracted using the MNDWI (modified normalized difference water index) method.Based on location monitoring of typical pond and regional sampling,the temporal and spatial variation characteristics of water quality of the ponds in Cangzhou were analyzed by ArcGIS software,the IDW（inverse distance weighted）was used to interpolate the salt content of pond water in the study area.The irrigation guarantee capacity of the pond water in the typical year was evaluated according to the variation characteristics of pond water quantity and quality and the irrigation water requirement characteristics of the main crop in the study area. Most of the water bodies in the ponds were distributed in the eastern region near the Bohai Sea and the northwest near Baiyangdian.The spatial distribution trend of pond water was more in the east and less in the west.From 1990 to 2019,the storage capacity of the pond water in the study area showed a growing trend,which was consistent with the changing trend of the local precipitation，but opposite to the changing trend of water surface evaporation.The salt mass concentration in pond water in eastern Cangzhou was more than 5 g/L,which was not suitable for agricultural irrigation.In the west and south of Cangzhou,the water quality (mass concentration) of ponds was less than 5 g/L,which could be used for agricultural irrigation.In the typical year of 2019,the amount of pond water that can be used for irrigation at the jointing stage and pre-winter of winter wheat was about 511 million m3 and about 533 million m3,respectively.It could guarantee an irrigation area with 6 807 km2 at the winter wheat jointing stage and 7 104 km2 pre-winter,respectively. The spatial distribution of pond water bodies in Cangzhou was roughly in the pattern of more in the east and less in the west.Meanwhile,the salt content of the pond water in the eastern region of the study area was higher than that in the western region.The distance from the Bohai Sea and topography were the main factors affecting the spatial distribution pattern of water quantity and quality of ponds in the study area.In recent 30 years,the water quantity of ponds has generally been increasing.Precipitation and evaporation were the major driving factors affecting the change of pond water quantity in the study area.The average annual water storage of ponds in Cangzhou city has reached 602 million m3.As an agricultural irrigation water source,pond water is of great significance to alleviate the water shortage in HLP area.
Hebei low plain (HLP) is one of the most important grain production bases in China.But,it is facing a shortage of freshwater resources problem from a long time.Ponds are important facilities for regulating and storing rainwater and flood resources in HLP area,and the utilization of pond water has attracted increasingly attention.With the continuous development in remote sensing technology,it is frequently applied to extract and analyse the water bodies such as ponds and wetlands,and it is main research means to study the temporal and spatial changes of pond water.However,there are few comprehensive studies on the quantity and quality of pond water at present.For HLP,the utilization value of unconventional pond water remains to be further studied. Cangzhou was taleen as a typical area of HLP.The quantity of the pond water in May and October of 1990,2000,2010,and 2019 in Cangzhou city were analyzed by the remote sensing technology,and the pond water was extracted using the MNDWI (modified normalized difference water index) method.Based on location monitoring of typical pond and regional sampling,the temporal and spatial variation characteristics of water quality of the ponds in Cangzhou were analyzed by ArcGIS software,the IDW（inverse distance weighted）was used to interpolate the salt content of pond water in the study area.The irrigation guarantee capacity of the pond water in the typical year was evaluated according to the variation characteristics of pond water quantity and quality and the irrigation water requirement characteristics of the main crop in the study area. Most of the water bodies in the ponds were distributed in the eastern region near the Bohai Sea and the northwest near Baiyangdian.The spatial distribution trend of pond water was more in the east and less in the west.From 1990 to 2019,the storage capacity of the pond water in the study area showed a growing trend,which was consistent with the changing trend of the local precipitation，but opposite to the changing trend of water surface evaporation.The salt mass concentration in pond water in eastern Cangzhou was more than 5 g/L,which was not suitable for agricultural irrigation.In the west and south of Cangzhou,the water quality (mass concentration) of ponds was less than 5 g/L,which could be used for agricultural irrigation.In the typical year of 2019,the amount of pond water that can be used for irrigation at the jointing stage and pre-winter of winter wheat was about 511 million m3 and about 533 million m3,respectively.It could guarantee an irrigation area with 6 807 km2 at the winter wheat jointing stage and 7 104 km2 pre-winter,respectively. The spatial distribution of pond water bodies in Cangzhou was roughly in the pattern of more in the east and less in the west.Meanwhile,the salt content of the pond water in the eastern region of the study area was higher than that in the western region.The distance from the Bohai Sea and topography were the main factors affecting the spatial distribution pattern of water quantity and quality of ponds in the study area.In recent 30 years,the water quantity of ponds has generally been increasing.Precipitation and evaporation were the major driving factors affecting the change of pond water quantity in the study area.The average annual water storage of ponds in Cangzhou city has reached 602 million m3.As an agricultural irrigation water source,pond water is of great significance to alleviate the water shortage in HLP area.
2021, 19(5):910-920.
Abstract:
Under the premise of climate change and the intensification of human activities,precipitation on a global scale shows obvious regional changes,has a certain impact on the natural environment and the development of human society.Therefore,studying the changes and laws of regional precipitation can not only promote the understanding of regional water cycle changes,but also have important significance for regional water resources protection,ecological construction,and sustainable and healthy economic development.The study of the hydrological cycle under climate change requires a long series of precipitation data,and the insufficient length of the existing data series is one of the main obstacles to climate change-related research. CRU applicability in the Haihe River basin (HRB) was analyzed from the perspectives of areal rainfall and site rainfall.To evaluate its system,the selected evaluation index is Pearson correlation coefficient (R),root mean square error (RMSE),mean absolute error (MAE),and bias. The applicability of CRU data in the Zhanghe River subbasin of the HRB is better than that of the entire HRB,and the evaluation results have reached the expected expectations.The mutation and periodicity test results are consistent with the previous analysis results based on the measured data.The difference in station density of the two river basins,the data processing method,and the error in the data itself make the evaluation results of the area rainfall of the two basins have a certain difference.Simultaneously,because CRU is 05° grid data,the HRB is affected by factors such as the limitation of the number of stations and the grid coverage area when the data is produced,which has certain limitations for restoring the measured data of the stations.Especially after 1990,there will be certain errors in the quality of the restored site data,which should be considered when using it in the future. CRU data can better reflect the rainfall change characteristics of the HRB and its subbasins,and compared to the HRB,CRU data in its subbasin of Zhanghe basin is more reliable.However,due to changes in the global observation sites of CRU data,the method of restoration and the uncertainty of the data itself should be fully considered when using the CRU data to research and restore the measured data at the site,especially after 1990.
Under the premise of climate change and the intensification of human activities,precipitation on a global scale shows obvious regional changes,has a certain impact on the natural environment and the development of human society.Therefore,studying the changes and laws of regional precipitation can not only promote the understanding of regional water cycle changes,but also have important significance for regional water resources protection,ecological construction,and sustainable and healthy economic development.The study of the hydrological cycle under climate change requires a long series of precipitation data,and the insufficient length of the existing data series is one of the main obstacles to climate change-related research. CRU applicability in the Haihe River basin (HRB) was analyzed from the perspectives of areal rainfall and site rainfall.To evaluate its system,the selected evaluation index is Pearson correlation coefficient (R),root mean square error (RMSE),mean absolute error (MAE),and bias. The applicability of CRU data in the Zhanghe River subbasin of the HRB is better than that of the entire HRB,and the evaluation results have reached the expected expectations.The mutation and periodicity test results are consistent with the previous analysis results based on the measured data.The difference in station density of the two river basins,the data processing method,and the error in the data itself make the evaluation results of the area rainfall of the two basins have a certain difference.Simultaneously,because CRU is 05° grid data,the HRB is affected by factors such as the limitation of the number of stations and the grid coverage area when the data is produced,which has certain limitations for restoring the measured data of the stations.Especially after 1990,there will be certain errors in the quality of the restored site data,which should be considered when using it in the future. CRU data can better reflect the rainfall change characteristics of the HRB and its subbasins,and compared to the HRB,CRU data in its subbasin of Zhanghe basin is more reliable.However,due to changes in the global observation sites of CRU data,the method of restoration and the uncertainty of the data itself should be fully considered when using the CRU data to research and restore the measured data at the site,especially after 1990.
2021, 19(5):921-929.
Abstract:
Ice thickness cover is an important index to judge and predict the disaster of ice in the Yellow River.The ice thickening and deglaciation process of the Yellow River during the freeze period is unique.The degreeday model suitable for the Inner Mongolia section of the Yellow River and the typical value of the empirical coefficient depends on the calibration of the field measured data.The heat that affects the thickness of ice cover mainly comes from the heat conduction between ice and atmosphere and the heat transfer between ice and water.The measured data show that the ice thickness varies greatly at different stations,which is not only due to the temperature change but also due to the discharge,velocity,and roughness.Based on the prototype observation data,the ice cover thickness in the Inner Mongolia section of the Yellow River was simulated. Colburn analogy method is used to calculate the heat flux under the ice cover,the factors such as river flow rate,water flow rate,river level slope and ice cover roughness are taken into account,and a model for calculating ice thickness is employed for degreeday method based on Stefan formula.Relevant parameters of the ice thickness calculation model are calibrated by the prototype observation data of four stations in the Bayangaolei to Toutaoguai reach.The calibrated model could calculate the ice thickness through the air temperature and water temperature data.Taking the ice thickness change near Toudaoguai observation station from 2015 to 2016 as an example,the ice thickness calculation formula introduced by Colburn analogy method is compared with the ice thickness calculation results of other formulas.The temperature data of Toudaoguai Station in the Inner Mongolia section of the Yellow River from 2006 to 2017 is analyzed.The ice thickness model is used to calculate the ice thickness during the freezing period from 2009 to 2010,when the cold degree was the coldest and the accumulated temperature value in winter was the largest.The results of different ice thickness calculation models under extreme weather conditions are compared. The results show that the ice thickness calculated by the ice thickness model is close to the measured ice thickness value.The accuracy of the improved ice thickness calculation model reaches 1.97%,which is improved compared with 14.99% of Stefan model,4.77% of the unified degree of the maturity model and 14.98% of dynamic water ice thickness radiation degree of the maturity model.The trend of ice thickness variation is consistent with the measured ice thickness variation trend.According to the accumulated temperature values and the characteristics of the temperature series,the temperature data of Toudaoguai station from 2006 to 2017 is analyzed.After analyzing the temperature data,it is found that the temperature changes in the short period of years under extreme weather conditions are more intense,and the average temperature in winter is also lower.For 2009–2010,when the cold degree was the coldest and the accumulated temperature value in winter was the largest,the accuracy of the model is 7.34%.In extreme weather,the accuracy of the model is higher,and the changing trend of ice thickness in the freeze period is similar to that in normal temperature. In most degree-day models,the convective heat transfer coefficient between ice cover and water body is calculated as a constant.The ice thickness calculation formula with the introduction of the Colburn analogy is improved in the accuracy of the ice thickness calculation results because the convective heat transfer coefficient between water and ice cover is not constant when considering the influence of under ice heat flux on the ice thickness.The calculated results of the model are in good agreement with the measured ice thickness data,which indicates that the model is suitable for the simulation of ice thickness in the Inner Mongolia section of the Yellow River,and can be used for the simulation of ice thickness variation at different points in the reach.The ice thickness calculation results of the improved model under both normal and extreme weather conditions maintain high accuracy,and the research results can provide a theoretical basis for the ice thickness calculation in the study area under extreme weather conditions.
Ice thickness cover is an important index to judge and predict the disaster of ice in the Yellow River.The ice thickening and deglaciation process of the Yellow River during the freeze period is unique.The degreeday model suitable for the Inner Mongolia section of the Yellow River and the typical value of the empirical coefficient depends on the calibration of the field measured data.The heat that affects the thickness of ice cover mainly comes from the heat conduction between ice and atmosphere and the heat transfer between ice and water.The measured data show that the ice thickness varies greatly at different stations,which is not only due to the temperature change but also due to the discharge,velocity,and roughness.Based on the prototype observation data,the ice cover thickness in the Inner Mongolia section of the Yellow River was simulated. Colburn analogy method is used to calculate the heat flux under the ice cover,the factors such as river flow rate,water flow rate,river level slope and ice cover roughness are taken into account,and a model for calculating ice thickness is employed for degreeday method based on Stefan formula.Relevant parameters of the ice thickness calculation model are calibrated by the prototype observation data of four stations in the Bayangaolei to Toutaoguai reach.The calibrated model could calculate the ice thickness through the air temperature and water temperature data.Taking the ice thickness change near Toudaoguai observation station from 2015 to 2016 as an example,the ice thickness calculation formula introduced by Colburn analogy method is compared with the ice thickness calculation results of other formulas.The temperature data of Toudaoguai Station in the Inner Mongolia section of the Yellow River from 2006 to 2017 is analyzed.The ice thickness model is used to calculate the ice thickness during the freezing period from 2009 to 2010,when the cold degree was the coldest and the accumulated temperature value in winter was the largest.The results of different ice thickness calculation models under extreme weather conditions are compared. The results show that the ice thickness calculated by the ice thickness model is close to the measured ice thickness value.The accuracy of the improved ice thickness calculation model reaches 1.97%,which is improved compared with 14.99% of Stefan model,4.77% of the unified degree of the maturity model and 14.98% of dynamic water ice thickness radiation degree of the maturity model.The trend of ice thickness variation is consistent with the measured ice thickness variation trend.According to the accumulated temperature values and the characteristics of the temperature series,the temperature data of Toudaoguai station from 2006 to 2017 is analyzed.After analyzing the temperature data,it is found that the temperature changes in the short period of years under extreme weather conditions are more intense,and the average temperature in winter is also lower.For 2009–2010,when the cold degree was the coldest and the accumulated temperature value in winter was the largest,the accuracy of the model is 7.34%.In extreme weather,the accuracy of the model is higher,and the changing trend of ice thickness in the freeze period is similar to that in normal temperature. In most degree-day models,the convective heat transfer coefficient between ice cover and water body is calculated as a constant.The ice thickness calculation formula with the introduction of the Colburn analogy is improved in the accuracy of the ice thickness calculation results because the convective heat transfer coefficient between water and ice cover is not constant when considering the influence of under ice heat flux on the ice thickness.The calculated results of the model are in good agreement with the measured ice thickness data,which indicates that the model is suitable for the simulation of ice thickness in the Inner Mongolia section of the Yellow River,and can be used for the simulation of ice thickness variation at different points in the reach.The ice thickness calculation results of the improved model under both normal and extreme weather conditions maintain high accuracy,and the research results can provide a theoretical basis for the ice thickness calculation in the study area under extreme weather conditions.
2021, 19(5):930-940.
Abstract:
With the rapid increase of population,agricultural water demand has increased largely,which resulted in the continuous construction of irrigation and water conservancy projects.The effect of artificial drive force on farmland water cycle has become more and more prominent,especially in the main grain-producing areas such as the North China Plain,which led to the "nature-society" duality of the farmland water cycle in the irrigated areas.In past years,the irrigation managers only focused on human living and economic benefits,while ignored the natural law and farmland sustainability,caused groundwater over-pumping and ecological environment deterioration,then influenced the high-quality agricultural production in the irrigated area.Thus,to solve the above problems,it is crucial to systematically illustrate the farmland water-cycle "health" and scientifically "diagnose" the related "symptoms". Based on the analysis on the structure and the corresponding health conception of farmland watercycle in irrigation areas,the evaluation index system of farmland watercycle health including four dimensions (water source,water transporting,water consumption,and water withdrawal & drainage) and fifteen indexes were established,according to the selection principle of Analytic Hierarchy Process.The indexes' weight through the combined Analytic Hierarchy Process-Entropy Weight Method were calculated to improve the corresponding objectivity.The threshold values of different health grades in the evaluation index system of farmland water-cycle were set according to the relevant national standards and reference to the related researches.Junliu irrigated area of Wei county,Hebei province was selected as the typical one of the North China Plain.The health of regional farmland water-cycle from 2010 to 2019 was evaluated through comprehensive index method and modified grey correlation analysis,respectively. The index evaluation results show that:the water quality,non-point water pollution of fertilizer and pesticide,and utilization coefficient of irrigation water are mostly "ill";the indexes such as water source diversity,the leakage proportion of canal irrigation water,the piping proportion of field irrigation water,the high-efficiency proportion of water-saving irrigation and reasonableness of planting structure have improved year by year in recent years.The total number of "normal" and healthier grades increased from four in 2010 to nine in 2019.The dimension evaluation results show that the health of water withdrawal and drainage is the worst and most of all are in "sick";while the health of the water source,water transport,and water consumption was improved year by year.The two comprehensive evaluation results both show that the water cycle in the Junliu irrigation area has been improved gradually in the recent decade.The evaluation results of grey correlation analysis show that the health grades of farmland watercycle are "seriously ill" from 2010 to 2015,then upgraded to "normal" in 2016,and reached a stable grade in 2017 and later maintain "sub-health".The scores of the comprehensive index method range from 2.36 to 3.58,and the corresponding health grade was gradually improved from "sick" in 2010 to "normal" after 2015. It is indicated that the comprehensive health of farmland water-cycle in Junliu irrigation area has gradually improved in the recent ten years due to the integrated management of groundwater over-pumping.The non-point water pollution of fertilizer and pesticide is the critical focus for the irrigation.The comprehensiveness and dimension health trends of grey correlation analysis and comprehensive index method are similar.By contrast,the results of grey correlation analysis are more reasonable as the healthy scores approach the critical value,while the results of the comprehensive index method are relatively objective to the whole trend indication.The results could provide a scientific basis and decision-making reference to the management and high-quality development of irrigated areas in the North China Plain.
With the rapid increase of population,agricultural water demand has increased largely,which resulted in the continuous construction of irrigation and water conservancy projects.The effect of artificial drive force on farmland water cycle has become more and more prominent,especially in the main grain-producing areas such as the North China Plain,which led to the "nature-society" duality of the farmland water cycle in the irrigated areas.In past years,the irrigation managers only focused on human living and economic benefits,while ignored the natural law and farmland sustainability,caused groundwater over-pumping and ecological environment deterioration,then influenced the high-quality agricultural production in the irrigated area.Thus,to solve the above problems,it is crucial to systematically illustrate the farmland water-cycle "health" and scientifically "diagnose" the related "symptoms". Based on the analysis on the structure and the corresponding health conception of farmland watercycle in irrigation areas,the evaluation index system of farmland watercycle health including four dimensions (water source,water transporting,water consumption,and water withdrawal & drainage) and fifteen indexes were established,according to the selection principle of Analytic Hierarchy Process.The indexes' weight through the combined Analytic Hierarchy Process-Entropy Weight Method were calculated to improve the corresponding objectivity.The threshold values of different health grades in the evaluation index system of farmland water-cycle were set according to the relevant national standards and reference to the related researches.Junliu irrigated area of Wei county,Hebei province was selected as the typical one of the North China Plain.The health of regional farmland water-cycle from 2010 to 2019 was evaluated through comprehensive index method and modified grey correlation analysis,respectively. The index evaluation results show that:the water quality,non-point water pollution of fertilizer and pesticide,and utilization coefficient of irrigation water are mostly "ill";the indexes such as water source diversity,the leakage proportion of canal irrigation water,the piping proportion of field irrigation water,the high-efficiency proportion of water-saving irrigation and reasonableness of planting structure have improved year by year in recent years.The total number of "normal" and healthier grades increased from four in 2010 to nine in 2019.The dimension evaluation results show that the health of water withdrawal and drainage is the worst and most of all are in "sick";while the health of the water source,water transport,and water consumption was improved year by year.The two comprehensive evaluation results both show that the water cycle in the Junliu irrigation area has been improved gradually in the recent decade.The evaluation results of grey correlation analysis show that the health grades of farmland watercycle are "seriously ill" from 2010 to 2015,then upgraded to "normal" in 2016,and reached a stable grade in 2017 and later maintain "sub-health".The scores of the comprehensive index method range from 2.36 to 3.58,and the corresponding health grade was gradually improved from "sick" in 2010 to "normal" after 2015. It is indicated that the comprehensive health of farmland water-cycle in Junliu irrigation area has gradually improved in the recent ten years due to the integrated management of groundwater over-pumping.The non-point water pollution of fertilizer and pesticide is the critical focus for the irrigation.The comprehensiveness and dimension health trends of grey correlation analysis and comprehensive index method are similar.By contrast,the results of grey correlation analysis are more reasonable as the healthy scores approach the critical value,while the results of the comprehensive index method are relatively objective to the whole trend indication.The results could provide a scientific basis and decision-making reference to the management and high-quality development of irrigated areas in the North China Plain.
2021, 19(5):941-949.
Abstract:
The excessive use of water resources,not only affects the sustainable development of the river basin or region but also destroys the water ecological environment to a certain extent.Therefore,it is necessary to conduct scientific accounting and regulation research on water resources,which not only guarantees the sustainable use of water resources but also maintains the healthy life of rivers,by studying the ecological base flow of rivers and ensure the maintenance of a certain flow in the river.The Luan River surrounds Beijing and Tianjin from the northwest to the southeast.It is an important and irreplaceable water conservation area and ecological support area for Beijing and Tianjin.It is also responsible for the important task of supplying water to Tianjin and Tangshan.As an important water resource link,the study of the ecological base flow of the Luan River is essential to ensure the healthy life of the Luan River. The current ecological base flow research of Luan River lacks a variety of hydrological methods to comprehensively analyzing the ecological base flow.Therefore,7 hydrological methods are used to calculate and analyze the ecological base flow of the typical section of Luan River. [JP+3]Monthly flow data of the Guojiatun hydrological station and Sandaohezi hydrological station from 1980 to 2016,the QP method,the tenant method,the frequency curve method,the typical hydrological frequency year method,the NGPRP(norther great plains resources program) method,and the driest monthly average flow in the past 10 years are used comprehensively.According to the characteristics of the runoff of different months in the Luan River during the flood period and the low water period,the upper and lower limits of the ecological base flow value of the relevant sections in each month are finely divided.The outcomes show that the ecological [JP]base flow value of the Sandaohezi section is from 1.10 m3/s to 6.06 m3/s,and the ecological base flow value of the Guojiatun section is from 0.78 m3/s to 5.66 m3/s.The monthly flow rate of the two sections for 37 years was tested with the above-determined ecological base flow value.The results showed that the ecological base flow in most months of the two sections for 37 years can be guaranteed.In two sections in December,January,and February the ecological base flow guarantee rate of the section is relatively low.[JP] The maximum ecological base flow at the Sandaohezi section of Luan River is 6.06 m3/s,the minimum ecological base flow is 1.10 m3/s,the maximum ecological base flow at the Guojiatun section is 5.66 m3/s,and the minimum ecological base flow is 0.78 m3/s,respectively.The QP method,frequency curve method,Tenant method (10%),the driest month average flow method in the past 10 years,focus on the ecological base flow during the dry period,and the calculated ecological base flow value is smaller.The NGPRP method focuses on the study of ecological base flow during normal water periods,and the calculated ecological base flow value is larger,which is suitable for rivers with sufficient water resources in the south to determine the use of ecological base flow.The ecological base flow guarantee rate of the two sections in December,January,and February are low.Measures such as reasonable division of water rights,scientific dispatching projects,the establishment of a monitoring system should be adopted to ensure the ecological base flow.
The excessive use of water resources,not only affects the sustainable development of the river basin or region but also destroys the water ecological environment to a certain extent.Therefore,it is necessary to conduct scientific accounting and regulation research on water resources,which not only guarantees the sustainable use of water resources but also maintains the healthy life of rivers,by studying the ecological base flow of rivers and ensure the maintenance of a certain flow in the river.The Luan River surrounds Beijing and Tianjin from the northwest to the southeast.It is an important and irreplaceable water conservation area and ecological support area for Beijing and Tianjin.It is also responsible for the important task of supplying water to Tianjin and Tangshan.As an important water resource link,the study of the ecological base flow of the Luan River is essential to ensure the healthy life of the Luan River. The current ecological base flow research of Luan River lacks a variety of hydrological methods to comprehensively analyzing the ecological base flow.Therefore,7 hydrological methods are used to calculate and analyze the ecological base flow of the typical section of Luan River. [JP+3]Monthly flow data of the Guojiatun hydrological station and Sandaohezi hydrological station from 1980 to 2016,the QP method,the tenant method,the frequency curve method,the typical hydrological frequency year method,the NGPRP(norther great plains resources program) method,and the driest monthly average flow in the past 10 years are used comprehensively.According to the characteristics of the runoff of different months in the Luan River during the flood period and the low water period,the upper and lower limits of the ecological base flow value of the relevant sections in each month are finely divided.The outcomes show that the ecological [JP]base flow value of the Sandaohezi section is from 1.10 m3/s to 6.06 m3/s,and the ecological base flow value of the Guojiatun section is from 0.78 m3/s to 5.66 m3/s.The monthly flow rate of the two sections for 37 years was tested with the above-determined ecological base flow value.The results showed that the ecological base flow in most months of the two sections for 37 years can be guaranteed.In two sections in December,January,and February the ecological base flow guarantee rate of the section is relatively low.[JP] The maximum ecological base flow at the Sandaohezi section of Luan River is 6.06 m3/s,the minimum ecological base flow is 1.10 m3/s,the maximum ecological base flow at the Guojiatun section is 5.66 m3/s,and the minimum ecological base flow is 0.78 m3/s,respectively.The QP method,frequency curve method,Tenant method (10%),the driest month average flow method in the past 10 years,focus on the ecological base flow during the dry period,and the calculated ecological base flow value is smaller.The NGPRP method focuses on the study of ecological base flow during normal water periods,and the calculated ecological base flow value is larger,which is suitable for rivers with sufficient water resources in the south to determine the use of ecological base flow.The ecological base flow guarantee rate of the two sections in December,January,and February are low.Measures such as reasonable division of water rights,scientific dispatching projects,the establishment of a monitoring system should be adopted to ensure the ecological base flow.
2021, 19(5):950-959,971.
Abstract:
Wheat is one of the main grain crops in China,and in 2019,China′s wheat production reached 133.6 million tons,accounting for 20% of total grain production.Climate change,especially the extreme climate,does a significant impact on winter wheat yield.Identifying the main influencing factors could help farmers to choose appropriate methods to alleviate the risk to wheat production.For different regions,the impact of climate change on winter wheat cultivation varies.Hebei Province is one of the main wheat-producing areas in China,and Ningjin County is the largest wheat-producing county in the plain area of Hebei.Therefore,it is important to analyze and identify the main climatic factors affecting wheat yield in the region and propose corresponding countermeasures to guide local agricultural production and guarantee high and stable crop yields. Mann-Kendall (M-K) trend test and Sen′s slope analysis were performed to obtain the trend of winter wheat production data and corresponding meteorological data from 1982 to 2018 in Ningjin County.The HP filter was used to separate winter wheat yield into climatic yield and trend yield,to screen the years with high yield variability,i.e.,three high yield years and three low yield years,and to reveal the main meteorological factors affecting yields,and then to analyze the relationship between winter wheat yield and climate change. The results showed that the average temperature (0.05 ℃·a-1),maximum temperature (0.03 ℃·a-1) and minimum temperature (0.07 ℃·a-1) in wheat season increased significantly,the average wind speed decreased significantly (-0.01 m·s-1·a-1),and the multi-year mean value of total ET0 was 600 mm with a not clear increasing trend.The multi-year average of actual winter wheat yield was 5 330kg·ha-1.Both the actual and trend yields showed a significant increasing trend with Sen′s slopes of 136 kg/(hm2·a-1) and 139 kg/(hm2·a-1),respectively.Though the climatic yield trend did not show a clear change trend,it varied from -1 245 to 1 376 kg·ha-1(-41%~26%),indicating a great variation in different years.The climate variables in big low yield and high yield seasons were analyzed and the main factors to influence wheat yield were summarized.Generally,extremely low temperature during the sowingregreening period (for example December 8 and 9,1986,the daily minimum temperature reached -21.2 ℃,and the average minimum temperature from January 14 to 25,1993 reached -14.1 ℃),un-sufficient irrigation during a jointingheading period (1993) and excessive precipitation in late planting period (2008) would lead to wheat yield reduction.The increases in sunshine hours and temperature are beneficial to wheat production. The trends of climate elements are consistent with the findings of most studies in the north China plain,indicating that climate change in the study area is consistent with the trends of climate change at larger spatial scales.Yields in the study area increased at a faster rate in the 1990′s,indicating a significant increase in the level of winter wheat cultivation during that period.The influence of climate factors on winter wheat yield in low yield years shows that extremely low temperatures during the sowingregreeningperiod,un-sufficient irrigation during the jointingheading period,and excessive precipitation in the late planting period can all lead to wheat yield reduction.The main meteorological factors causing yield reduction varied with growth seasons,indicating the complexity of climate effects on wheat yield production.The influence of climate factors on winter wheat yield in highyielding years shows that the increase in sunshine hours is more beneficial to wheat yield under the condition that the temperature remains consistent with the multi-year average.The main meteorological factors causing yield increase are similar in different years,indicating the consistency of climate factors on wheat yield increase.
Wheat is one of the main grain crops in China,and in 2019,China′s wheat production reached 133.6 million tons,accounting for 20% of total grain production.Climate change,especially the extreme climate,does a significant impact on winter wheat yield.Identifying the main influencing factors could help farmers to choose appropriate methods to alleviate the risk to wheat production.For different regions,the impact of climate change on winter wheat cultivation varies.Hebei Province is one of the main wheat-producing areas in China,and Ningjin County is the largest wheat-producing county in the plain area of Hebei.Therefore,it is important to analyze and identify the main climatic factors affecting wheat yield in the region and propose corresponding countermeasures to guide local agricultural production and guarantee high and stable crop yields. Mann-Kendall (M-K) trend test and Sen′s slope analysis were performed to obtain the trend of winter wheat production data and corresponding meteorological data from 1982 to 2018 in Ningjin County.The HP filter was used to separate winter wheat yield into climatic yield and trend yield,to screen the years with high yield variability,i.e.,three high yield years and three low yield years,and to reveal the main meteorological factors affecting yields,and then to analyze the relationship between winter wheat yield and climate change. The results showed that the average temperature (0.05 ℃·a-1),maximum temperature (0.03 ℃·a-1) and minimum temperature (0.07 ℃·a-1) in wheat season increased significantly,the average wind speed decreased significantly (-0.01 m·s-1·a-1),and the multi-year mean value of total ET0 was 600 mm with a not clear increasing trend.The multi-year average of actual winter wheat yield was 5 330kg·ha-1.Both the actual and trend yields showed a significant increasing trend with Sen′s slopes of 136 kg/(hm2·a-1) and 139 kg/(hm2·a-1),respectively.Though the climatic yield trend did not show a clear change trend,it varied from -1 245 to 1 376 kg·ha-1(-41%~26%),indicating a great variation in different years.The climate variables in big low yield and high yield seasons were analyzed and the main factors to influence wheat yield were summarized.Generally,extremely low temperature during the sowingregreening period (for example December 8 and 9,1986,the daily minimum temperature reached -21.2 ℃,and the average minimum temperature from January 14 to 25,1993 reached -14.1 ℃),un-sufficient irrigation during a jointingheading period (1993) and excessive precipitation in late planting period (2008) would lead to wheat yield reduction.The increases in sunshine hours and temperature are beneficial to wheat production. The trends of climate elements are consistent with the findings of most studies in the north China plain,indicating that climate change in the study area is consistent with the trends of climate change at larger spatial scales.Yields in the study area increased at a faster rate in the 1990′s,indicating a significant increase in the level of winter wheat cultivation during that period.The influence of climate factors on winter wheat yield in low yield years shows that extremely low temperatures during the sowingregreeningperiod,un-sufficient irrigation during the jointingheading period,and excessive precipitation in the late planting period can all lead to wheat yield reduction.The main meteorological factors causing yield reduction varied with growth seasons,indicating the complexity of climate effects on wheat yield production.The influence of climate factors on winter wheat yield in highyielding years shows that the increase in sunshine hours is more beneficial to wheat yield under the condition that the temperature remains consistent with the multi-year average.The main meteorological factors causing yield increase are similar in different years,indicating the consistency of climate factors on wheat yield increase.
2021, 19(5):960-971.
Abstract:
Frequent drought events threaten the agricultural water cycle and food security in western Heilongjiang Province.Understanding the water supply-requirement relationship is vital to the exploration of drought mechanisms.The reference crop evapotranspiration (ET0),crop water requirement (ETc) and irrigation water requirement (Ir) during the maize growth period were calculated and irrigation schedules were formulated by the FAO-56single crop coefficient method.The water requirement deficit or surplus of maize was analyzed with the crop water surplus deficit index (CW).The results showed that ET0 and ETc decreased,while effective precipitation (Pe),Ir,and CW displayed an increasing trend in the maize growth period in western Heilongjiang Province from 1960 to 2015.The average ET0,ETc,Pe,and Ir were 639.64,438.13,224.40,and 273.87 mm,respectively.Drought conditions varied in different hydrological years,and it was challenging for Pe to meet maize ETc.Therefore,irrigation schedules were formulated for different hydrological years.The average net irrigation quotas of rainy year,normal year,dry year and extremely dry year were 152.43,236.33,276.53,and 353.47 mm,respectively.Analyzing the water requirement deficit or surplus of maize helps better understand the effect of drought on agricultural development.
Frequent drought events threaten the agricultural water cycle and food security in western Heilongjiang Province.Understanding the water supply-requirement relationship is vital to the exploration of drought mechanisms.The reference crop evapotranspiration (ET0),crop water requirement (ETc) and irrigation water requirement (Ir) during the maize growth period were calculated and irrigation schedules were formulated by the FAO-56single crop coefficient method.The water requirement deficit or surplus of maize was analyzed with the crop water surplus deficit index (CW).The results showed that ET0 and ETc decreased,while effective precipitation (Pe),Ir,and CW displayed an increasing trend in the maize growth period in western Heilongjiang Province from 1960 to 2015.The average ET0,ETc,Pe,and Ir were 639.64,438.13,224.40,and 273.87 mm,respectively.Drought conditions varied in different hydrological years,and it was challenging for Pe to meet maize ETc.Therefore,irrigation schedules were formulated for different hydrological years.The average net irrigation quotas of rainy year,normal year,dry year and extremely dry year were 152.43,236.33,276.53,and 353.47 mm,respectively.Analyzing the water requirement deficit or surplus of maize helps better understand the effect of drought on agricultural development.
2021, 19(5):972-981.
Abstract:
Geological hazards frequently occurred in China due to its complex geographical location.Landslides are characterized by the outbreak and destructive impacts,threaten the lives and property of civilians are regularly reported in mountainous areas of China.Therefore,predicting dangerous areas of the landslide has significant importance to estimate the affected area and loss,and to protect people′s property and life safety.A method is tried to find for the prediction of the longest horizontal travel distance of the landslide combining K-fold cross-validation and deep learning theory due to complex factors that are hard to find. Jianshanying landslide is a high slope in Faer Town,Shuicheng County,Guizhou Province,and its failure may cause a great loss.A deep neural network model of the high slope′s hazard zone was established to carry out a nonlinear prediction.Five factors are integrated based on its locomotion length studied by foreign and domestic academics,which do not exist multicollinearity,including the largest discrepancy in elevation,the volume,slope gradient,slope angle,and stratum dip angle.Typical rainfall-causing landslide cases in the southwest part of China are also collected by reviewing relevant literature and documentation.The parameters selected from these cases are evaluated by multiple linear regression and random forest regressor to sufficiently understand their feature.Besides,due to the size of the data set,the deep learning theory is applied to the dangerous areas prediction of the landslide with the K-fold cross-validation method.The deep neural network model is built and continuously optimized base on the training data of these cases.Generalization ability is tested by the K-fold cross-validation method,and the best model has been selected.The largest locomotion length,namely the dangerous areas of the landslide,is predicted. The largest discrepancy in elevation of the front edge and back edge of the landslide is the most significant factor in predicting the longest horizontal travel distance of the landslide.Multiple linear regression model is not suitable to solve this issue,except for the discrepancy in elevation.The P-values of its intercept and other indicators are all larger than 5%,so there is no enough evidence to reject the hypothesis H0,their regression coefficients are equal to zero.Besides,according to the model training and prediction,the loss curve shows a staged decrease,dropping to 0.17,which achieves a convergence and displays its good generalization ability.After model training,using the nine examples of testing data to input into the model and compared with the actual target distance,except for the example in Liena,Tibet,the relative errors of the others are between -14% and 14% while their absolute errors are between -160 m and 160 m. The elevation is the main factor,while the volume,slope gradient,slope angle,and stratum dip angle are of equal importance in prediction indicators.The deep neuron network model is highly authoritative and has good generalization ability,so it tends to predict the travel distance of the landslide.After the relevant factors of the Jianshanying landslide are input into model,the result illustrates that the hazard zone starting from its back edge within the linear distance of landslide direction is 1 769 m.
Geological hazards frequently occurred in China due to its complex geographical location.Landslides are characterized by the outbreak and destructive impacts,threaten the lives and property of civilians are regularly reported in mountainous areas of China.Therefore,predicting dangerous areas of the landslide has significant importance to estimate the affected area and loss,and to protect people′s property and life safety.A method is tried to find for the prediction of the longest horizontal travel distance of the landslide combining K-fold cross-validation and deep learning theory due to complex factors that are hard to find. Jianshanying landslide is a high slope in Faer Town,Shuicheng County,Guizhou Province,and its failure may cause a great loss.A deep neural network model of the high slope′s hazard zone was established to carry out a nonlinear prediction.Five factors are integrated based on its locomotion length studied by foreign and domestic academics,which do not exist multicollinearity,including the largest discrepancy in elevation,the volume,slope gradient,slope angle,and stratum dip angle.Typical rainfall-causing landslide cases in the southwest part of China are also collected by reviewing relevant literature and documentation.The parameters selected from these cases are evaluated by multiple linear regression and random forest regressor to sufficiently understand their feature.Besides,due to the size of the data set,the deep learning theory is applied to the dangerous areas prediction of the landslide with the K-fold cross-validation method.The deep neural network model is built and continuously optimized base on the training data of these cases.Generalization ability is tested by the K-fold cross-validation method,and the best model has been selected.The largest locomotion length,namely the dangerous areas of the landslide,is predicted. The largest discrepancy in elevation of the front edge and back edge of the landslide is the most significant factor in predicting the longest horizontal travel distance of the landslide.Multiple linear regression model is not suitable to solve this issue,except for the discrepancy in elevation.The P-values of its intercept and other indicators are all larger than 5%,so there is no enough evidence to reject the hypothesis H0,their regression coefficients are equal to zero.Besides,according to the model training and prediction,the loss curve shows a staged decrease,dropping to 0.17,which achieves a convergence and displays its good generalization ability.After model training,using the nine examples of testing data to input into the model and compared with the actual target distance,except for the example in Liena,Tibet,the relative errors of the others are between -14% and 14% while their absolute errors are between -160 m and 160 m. The elevation is the main factor,while the volume,slope gradient,slope angle,and stratum dip angle are of equal importance in prediction indicators.The deep neuron network model is highly authoritative and has good generalization ability,so it tends to predict the travel distance of the landslide.After the relevant factors of the Jianshanying landslide are input into model,the result illustrates that the hazard zone starting from its back edge within the linear distance of landslide direction is 1 769 m.
2021, 19(5):982-989.
Abstract:
To scientifically and reasonably evaluate the safety status of an aqueduct in the water diversion project operation period in northwest China,it is of great significance to put forward an objective and reliable aqueduct disease safety evaluation system and method by analyzing the influence of geology,complex environment,climate conditions and various adverse factors during the operation period of an aqueduct. On the basis of the existing aqueduct disease evaluation research,combined with the common disease problems of aqueducts in the operation period,the evaluation index system of aqueduct disease is put forward in northwest China.Thirteen aqueduct disease evaluation indexes are constructed from four aspects of material deterioration,apparent damage,structural deformation and leakage,and the judgment standards of each index are given.The safety evaluation grade of aqueduct disease is divided into four grades:A,B,C,and D.Grade A indicates that the structure has no defects that affect normal operation,and normal operation can be ensured by routine maintenance.Grade B indicates that the structure is slightly damaged and can reach normal operation after partial maintenance.Grade C indicates that the structure is seriously damaged,and the normal operation can only be achieved after overhaul.Grade D indicates that the structure is seriously damaged and needs to be scrapped,rebuilt,or reduced to standard.The projection pursuit model is used for safety evaluation,and the improved particle swarm optimization (IPSO) algorithm is used to optimize the best projection direction of the projection pursuit (PP) model.The weight of each evaluation index of aqueduct disease is calculated.Combined with the logistic curve function,the aqueduct disease safety evaluation model based on IPSO-PP is constructed,and the evaluation grade of each aqueduct disease is identified. The optimization model is used for empirical analysis by taking six typical aqueducts as the research objects.According to the value of projection direction of each index,the sensitivity factors affecting aqueduct safety,such as deflection deformation of aqueduct body,crack width,concrete strength,and concrete carbonation,are identified.The disease evaluation grade of aqueducts No.2,No.4,No.14 and No.15 are grade B.The disease grade of No.5 and No.6 aqueduct are grade C,and the evaluation results are consistent with the actual situation,which shows that the method is scientific and reasonable.The results show that IPSO is better than Particle Swarm Optimization Algorithm and Differential Evolution Algorithm,and it has strong optimization ability and better solution accuracy,and the optimization algorithm is relatively stable. Given the common diseases of aqueducts in the operation period of water diversion projects in northwest China,a complete set of safety evaluation index system of aqueduct diseases is established from four aspects of aqueduct material deterioration,apparent damage,structural deformation and water leakage,fully considering its complex geographical and climatic characteristics.Referring to the evaluation methods and theories in other related fields,the IPSO-PP aqueduct safety evaluation model based on an intelligent optimization algorithm is constructed.The established safety evaluation index system of aqueduct disease in northwest China and IPSO-PP aqueduct safety evaluation model is introduced into an example to obtain the evaluation results which are consistent with the actual situation of the project and the analysis and comparison model.It shows that the proposed safety evaluation index system and evaluation method for an aqueduct in northwest China can ensure the reliability and objectivity of the evaluation results.It provides a reference for the safety evaluation of aqueduct diseases in northwest China.
To scientifically and reasonably evaluate the safety status of an aqueduct in the water diversion project operation period in northwest China,it is of great significance to put forward an objective and reliable aqueduct disease safety evaluation system and method by analyzing the influence of geology,complex environment,climate conditions and various adverse factors during the operation period of an aqueduct. On the basis of the existing aqueduct disease evaluation research,combined with the common disease problems of aqueducts in the operation period,the evaluation index system of aqueduct disease is put forward in northwest China.Thirteen aqueduct disease evaluation indexes are constructed from four aspects of material deterioration,apparent damage,structural deformation and leakage,and the judgment standards of each index are given.The safety evaluation grade of aqueduct disease is divided into four grades:A,B,C,and D.Grade A indicates that the structure has no defects that affect normal operation,and normal operation can be ensured by routine maintenance.Grade B indicates that the structure is slightly damaged and can reach normal operation after partial maintenance.Grade C indicates that the structure is seriously damaged,and the normal operation can only be achieved after overhaul.Grade D indicates that the structure is seriously damaged and needs to be scrapped,rebuilt,or reduced to standard.The projection pursuit model is used for safety evaluation,and the improved particle swarm optimization (IPSO) algorithm is used to optimize the best projection direction of the projection pursuit (PP) model.The weight of each evaluation index of aqueduct disease is calculated.Combined with the logistic curve function,the aqueduct disease safety evaluation model based on IPSO-PP is constructed,and the evaluation grade of each aqueduct disease is identified. The optimization model is used for empirical analysis by taking six typical aqueducts as the research objects.According to the value of projection direction of each index,the sensitivity factors affecting aqueduct safety,such as deflection deformation of aqueduct body,crack width,concrete strength,and concrete carbonation,are identified.The disease evaluation grade of aqueducts No.2,No.4,No.14 and No.15 are grade B.The disease grade of No.5 and No.6 aqueduct are grade C,and the evaluation results are consistent with the actual situation,which shows that the method is scientific and reasonable.The results show that IPSO is better than Particle Swarm Optimization Algorithm and Differential Evolution Algorithm,and it has strong optimization ability and better solution accuracy,and the optimization algorithm is relatively stable. Given the common diseases of aqueducts in the operation period of water diversion projects in northwest China,a complete set of safety evaluation index system of aqueduct diseases is established from four aspects of aqueduct material deterioration,apparent damage,structural deformation and water leakage,fully considering its complex geographical and climatic characteristics.Referring to the evaluation methods and theories in other related fields,the IPSO-PP aqueduct safety evaluation model based on an intelligent optimization algorithm is constructed.The established safety evaluation index system of aqueduct disease in northwest China and IPSO-PP aqueduct safety evaluation model is introduced into an example to obtain the evaluation results which are consistent with the actual situation of the project and the analysis and comparison model.It shows that the proposed safety evaluation index system and evaluation method for an aqueduct in northwest China can ensure the reliability and objectivity of the evaluation results.It provides a reference for the safety evaluation of aqueduct diseases in northwest China.
2021, 19(5):990-998.1006.
Abstract:
To solve the problem of uneven distribution of water resources,numerous interbasin water transfer projects have been built in China,including a great number of large aqueducts.After decades of operation,the aqueduct structure is prone to aging and damage,which has certain potential safety hazards.Shuguang aqueduct is one of the important buildings of the third main channel of the Red Flag Canal.The aqueduct has a total length of 550.0 m,a maximum height of 16.0 m,a bottom width of 5.4 m,and a top width of 3.5 m.The aqueduct is a masonry aqueduct,and its main buildings include upstream approach canal,aqueduct body,arch structure,main arch ring,pier and abutment,and downstream approach canal.After more than 50 years' operation,the on-site inspection found that the jointing materials between masonry were aged and weathered,and the upper structure of the upstream approach canal,aqueduct,and downstream approach canal or trough body,especially the mortar in the top area,was seriously out of joint,which deserved attention.Based on ABAQUS software and homogenization theory,a three-dimensional finite element calculation model of the aqueduct was established to calculate the stress,deformation,and foundation settlement distribution of the whole structure of the aqueduct under different working conditions.Furthermore,the influence of differential load and temperature load on the aqueduct structure was presented.Finally,the structural safety of the aqueduct was comprehensively evaluated. Under different load conditions,the maximum compressive stress of each pier of the Shuguang aqueduct was mainly distributed at the contact position between abutment and pier.The maximum tensile stress of each pier appeared at the bottom of the abutment of the pier.The maximum compressive stress and tensile stress were 2.90 MPa and 2.29 MPa,respectively.The tensile stress of the pier exceeded the tensile strength of the masonry cementitious material but only occurred in a small local area.However,when the temperature dropped,the pier was greatly affected by tensile force,and the tensile stress in the middle of the pier and the bottom of the pier exceeded the tensile strength of masonry cementitious material,which had a great influence on the structure of the pier.Under the action of static load,the transverse displacement of the aqueduct was mainly located in the middle of the aqueduct,the longitudinal displacement was mainly distributed at both ends of the aqueduct structure.The settlement of the aqueduct was mainly located on the leeward side of the pier and abutment.The maximum settlement of pier foundation and settlement difference of adjacent pier foundation under each working condition appeared in Condition 6,with the maximum settlement value of 1.57 mm and the maximum settlement difference of 1.07 mm.The settlement difference of the aqueduct and adjacent pier was less than the allowable value of 100 mm and 50 mm,respectively,which can meet the requirements.The differential load and temperature load on the aqueduct pier would cause horizontal tensile stress in the middle of the pier,which caused longitudinal cracks.The sudden drop in air temperature induce surface temperature cracks in the aqueduct pier,but it did not affect the deep part of the pier structure.Two suggestions were proposed,including strengthening deformation monitoring in the middle of the pier and repairing the surface cracks. Through comprehensive analysis,it indicated that the structural safety of the aqueduct was recognized as Class B.The research methods and achievements can provide a reference for structural stress and deformation analysis and safety evaluation of similar aqueduct projects.
To solve the problem of uneven distribution of water resources,numerous interbasin water transfer projects have been built in China,including a great number of large aqueducts.After decades of operation,the aqueduct structure is prone to aging and damage,which has certain potential safety hazards.Shuguang aqueduct is one of the important buildings of the third main channel of the Red Flag Canal.The aqueduct has a total length of 550.0 m,a maximum height of 16.0 m,a bottom width of 5.4 m,and a top width of 3.5 m.The aqueduct is a masonry aqueduct,and its main buildings include upstream approach canal,aqueduct body,arch structure,main arch ring,pier and abutment,and downstream approach canal.After more than 50 years' operation,the on-site inspection found that the jointing materials between masonry were aged and weathered,and the upper structure of the upstream approach canal,aqueduct,and downstream approach canal or trough body,especially the mortar in the top area,was seriously out of joint,which deserved attention.Based on ABAQUS software and homogenization theory,a three-dimensional finite element calculation model of the aqueduct was established to calculate the stress,deformation,and foundation settlement distribution of the whole structure of the aqueduct under different working conditions.Furthermore,the influence of differential load and temperature load on the aqueduct structure was presented.Finally,the structural safety of the aqueduct was comprehensively evaluated. Under different load conditions,the maximum compressive stress of each pier of the Shuguang aqueduct was mainly distributed at the contact position between abutment and pier.The maximum tensile stress of each pier appeared at the bottom of the abutment of the pier.The maximum compressive stress and tensile stress were 2.90 MPa and 2.29 MPa,respectively.The tensile stress of the pier exceeded the tensile strength of the masonry cementitious material but only occurred in a small local area.However,when the temperature dropped,the pier was greatly affected by tensile force,and the tensile stress in the middle of the pier and the bottom of the pier exceeded the tensile strength of masonry cementitious material,which had a great influence on the structure of the pier.Under the action of static load,the transverse displacement of the aqueduct was mainly located in the middle of the aqueduct,the longitudinal displacement was mainly distributed at both ends of the aqueduct structure.The settlement of the aqueduct was mainly located on the leeward side of the pier and abutment.The maximum settlement of pier foundation and settlement difference of adjacent pier foundation under each working condition appeared in Condition 6,with the maximum settlement value of 1.57 mm and the maximum settlement difference of 1.07 mm.The settlement difference of the aqueduct and adjacent pier was less than the allowable value of 100 mm and 50 mm,respectively,which can meet the requirements.The differential load and temperature load on the aqueduct pier would cause horizontal tensile stress in the middle of the pier,which caused longitudinal cracks.The sudden drop in air temperature induce surface temperature cracks in the aqueduct pier,but it did not affect the deep part of the pier structure.Two suggestions were proposed,including strengthening deformation monitoring in the middle of the pier and repairing the surface cracks. Through comprehensive analysis,it indicated that the structural safety of the aqueduct was recognized as Class B.The research methods and achievements can provide a reference for structural stress and deformation analysis and safety evaluation of similar aqueduct projects.
2021, 19(5):999-1006.
Abstract:
The local scour of bridge piers is intensified by the existence of ice cover.Correct calculation of local scour pit depth of bridge piers under ice cover is very important for the safety design of bridge.Many experts and scholars studies the free flow under the condition of bridge pier local scour pit depth by experimental research and artificial intelligence method.The study of bridge pier local scour problem under the condition of ice compared to the free flow conditions in terms of local scour of bridge piers research started late,and the research is relatively small,so the use of artificial intelligence method is helpful to predict the laboratory bridge pier local scour pit depth. Based on the principle of dimensional analysis,the relevant factors affecting the local scour of bridge piers were analyzed by the support vector machine (SVM) and BP neural network based on the experimental data of local scour of bridge piers under the conditions of clear water scour in the laboratory.Three-quarters of the test data were taken as the training data set of the scour pit prediction model,and one-fourth as the test data set of the scour pit prediction model.When calculating the local scour pit depth of bridge pier under the condition of open flow,the input factors of the model are:flow Froude number Fr,the ratio of water depth to pier diameter h/D,the ratio of median particle size of bed sand to pier diameter d50/D.Output factor:scour pit depth ds.The local scour pit depth of bridge piers were calculated using the 65-1 and 65-2 revisions in the Chinese Highway Engineering Hydrological Survey and Design Code (2015) and the HEC-18 formula in the American Code,and the calculated results were compared with the predicted results of SVM and BP neural network model. When predicting the local scour pit depth of bridge pier under ice sheet conditions,the input factors of the model are:flow Froude number Fr,the ratio of water depth to pier diameter h/D,the ratio of median particle size of bed sand to pier diameter d50/D,the ratio of ice cover roughness to channel bed roughness ni/nb.Output factor:scour pit depth DS,and the predicted results are compared with the test results.The correlation coefficient (r),root mean square error (δRMSE),mean absolute percentage error (δMAPE),and determination coefficient (R2) was used as the evaluation indexes of the prediction results.When predicting the local scour pit depth of the bridge pier under the condition of open flow,the rof BP neural network model and SVM model are 0.89 and 0.88,and δMAPE is 38.8% and 31%,respectively.The rand δMAPEof local scour pit depth of piers are 0.83 and 0.53 cm,respectively,and 61.2% and 189%,respectively,according to Chinese code formula and American code formula.When predicting the scour pit depth under ice sheet conditions,the predicted r values are 0.78 and 0.73,and δMAPEvalues are 43% and 46%,respectively. By integrating the test data of pier local scour under the current ice sheet and open flow conditions,the depth of the pier local scour pit was predicted by BP neural network model,SVM model,Chinese code,and American code.It is found that the study of pier local scour under open flow is enlightening,and the relationship between pier local scour depth and water depth,velocity,and pier diameter under open flow and ice cover is significant,there is a nonlinear relationship between the influence factors.When the BP neural network model and SVM model were used to predict the local scour depth of bridge piers under open flow,the accuracy is generally higher than the calculation results of Chinese code and American code.BP neural network model and SVM model showed good performance in predicting the local scour pit depth of bridge piers under open flow and ice cap,and the prediction results have high accuracy,which can provide a certain reference for the safety design of bridges.
The local scour of bridge piers is intensified by the existence of ice cover.Correct calculation of local scour pit depth of bridge piers under ice cover is very important for the safety design of bridge.Many experts and scholars studies the free flow under the condition of bridge pier local scour pit depth by experimental research and artificial intelligence method.The study of bridge pier local scour problem under the condition of ice compared to the free flow conditions in terms of local scour of bridge piers research started late,and the research is relatively small,so the use of artificial intelligence method is helpful to predict the laboratory bridge pier local scour pit depth. Based on the principle of dimensional analysis,the relevant factors affecting the local scour of bridge piers were analyzed by the support vector machine (SVM) and BP neural network based on the experimental data of local scour of bridge piers under the conditions of clear water scour in the laboratory.Three-quarters of the test data were taken as the training data set of the scour pit prediction model,and one-fourth as the test data set of the scour pit prediction model.When calculating the local scour pit depth of bridge pier under the condition of open flow,the input factors of the model are:flow Froude number Fr,the ratio of water depth to pier diameter h/D,the ratio of median particle size of bed sand to pier diameter d50/D.Output factor:scour pit depth ds.The local scour pit depth of bridge piers were calculated using the 65-1 and 65-2 revisions in the Chinese Highway Engineering Hydrological Survey and Design Code (2015) and the HEC-18 formula in the American Code,and the calculated results were compared with the predicted results of SVM and BP neural network model. When predicting the local scour pit depth of bridge pier under ice sheet conditions,the input factors of the model are:flow Froude number Fr,the ratio of water depth to pier diameter h/D,the ratio of median particle size of bed sand to pier diameter d50/D,the ratio of ice cover roughness to channel bed roughness ni/nb.Output factor:scour pit depth DS,and the predicted results are compared with the test results.The correlation coefficient (r),root mean square error (δRMSE),mean absolute percentage error (δMAPE),and determination coefficient (R2) was used as the evaluation indexes of the prediction results.When predicting the local scour pit depth of the bridge pier under the condition of open flow,the rof BP neural network model and SVM model are 0.89 and 0.88,and δMAPE is 38.8% and 31%,respectively.The rand δMAPEof local scour pit depth of piers are 0.83 and 0.53 cm,respectively,and 61.2% and 189%,respectively,according to Chinese code formula and American code formula.When predicting the scour pit depth under ice sheet conditions,the predicted r values are 0.78 and 0.73,and δMAPEvalues are 43% and 46%,respectively. By integrating the test data of pier local scour under the current ice sheet and open flow conditions,the depth of the pier local scour pit was predicted by BP neural network model,SVM model,Chinese code,and American code.It is found that the study of pier local scour under open flow is enlightening,and the relationship between pier local scour depth and water depth,velocity,and pier diameter under open flow and ice cover is significant,there is a nonlinear relationship between the influence factors.When the BP neural network model and SVM model were used to predict the local scour depth of bridge piers under open flow,the accuracy is generally higher than the calculation results of Chinese code and American code.BP neural network model and SVM model showed good performance in predicting the local scour pit depth of bridge piers under open flow and ice cap,and the prediction results have high accuracy,which can provide a certain reference for the safety design of bridges.
2021, 19(5):1007-1013,1023.
Abstract:
Traditional underflow energy dissipators were mostly used in small and medium-sized projects,and they were rarely used in high dam discharge energy dissipation.In recent years,as people′s requirements for the ecological environment have increased,environmentally-friendly stilling basins with drop sill and sudden expansion had been well used in many projects in high-head and large-unit-wide flow projects.The fluctuating water pressure on the bottom of the stilling pool is extremely destructive.Many of the bottoms of the stilling pool had been damaged during operation in the domestic and foreign-built projects.There were many results of previous studies on the fluctuating pressure characteristics of the stilling pool,but there are few studies on the fluctuating pressure characteristics of the stilling pool with drop sill and sudden expansion,especially the related characteristics and spectral characteristics are not involved. Based on the results of physical model tests,the fluctuating pressure characteristics of the bottom plate of the stilling pool were studied with drop sill and sudden expansion and the stilling pool were analyzed with drop sill and sudden expansion (β=1.3,1.6) and the non-sudden expansion stilling pool(β=1.0).The research results of the amplitude characteristics,correlation characteristics,and frequency characteristics of the fluctuating pressure of the bottom plate of the stilling pool can provide a reference and guidance for engineering design. It was found that under different hydraulic conditions,the fluctuating pressure coefficient of the midline of the bottom of the suddenly and non-suddenly expanded stilling pools showed a trend of attenuation along the way,the peak appeared at the head of the stilling pool,and the fluctuating pressure coefficient increased with the increase of the flow energy ratio.Compared with the non-sudden expansion stilling pool,the stilling pool with drop sill and sudden expansion can significantly reduce the fluctuating pressure level of the bottom plate.The probability density of fluctuating pressure in the impingement zone and the wall jet zone conforms to the normal distribution.Under the conditions of different flow energy ratios,the spatial integration scale distribution law of the fluctuating pressure of the bottom of the sudden expansion stilling pool was the same,and all increased along the flow direction,and the spatial integration scale and the fluctuating pressure energy of the sudden expansion stilling pool were significantly lower than that of the non-sudden expansion stilling pool. Under the same hydraulic conditions,the central line fluctuating pressure coefficient of the stilling pool with drop sill and sudden expansion was the same as the non-sudden expansion-type distribution law,and the maximum value of the fluctuating pressure coefficient appeared at the head of the pool.It decayed gradually along the way,and the stilling pool with drop sill and sudden expansion decayed more rapidly.Compared with the non-sudden expansion stilling pool,the sudden expansion stilling pool can significantly reduce the fluctuating pressure level of the bottom plate.The maximum value of the sudden expansion ratio of 1.3 is reduced by 63%,and the maximum value of the sudden expansion ratio of 1.6 is reduced by 42%.The probability density of the fluctuating pressure of the sudden expansion stilling pool conforms to the normal distribution.In the impact area,the spatial integral scale of the sudden expansion type stilling pool was significantly lower than that of the non-sudden expansion type.Its vortex retention was low,accompanied by the continuous generation and fragmentation of the vortex.The predominant frequency of the fluctuating pressure of the sudden expansion stilling pool shifted to high frequency,from 4 Hz to 8 Hz,the possibility of pressure pulsation causing the bottom plate to resonate was very small.However,there was the possibility of resonance in the drop and sudden expansion parts,which should be paid attention.In the engineering design,the relationship between the strength of the fluctuating pressure and the dominant frequency should be comprehensively considered.Under the premise of no resonance,it was beneficial to the project to appropriately reduce the fluctuating pressure.
Traditional underflow energy dissipators were mostly used in small and medium-sized projects,and they were rarely used in high dam discharge energy dissipation.In recent years,as people′s requirements for the ecological environment have increased,environmentally-friendly stilling basins with drop sill and sudden expansion had been well used in many projects in high-head and large-unit-wide flow projects.The fluctuating water pressure on the bottom of the stilling pool is extremely destructive.Many of the bottoms of the stilling pool had been damaged during operation in the domestic and foreign-built projects.There were many results of previous studies on the fluctuating pressure characteristics of the stilling pool,but there are few studies on the fluctuating pressure characteristics of the stilling pool with drop sill and sudden expansion,especially the related characteristics and spectral characteristics are not involved. Based on the results of physical model tests,the fluctuating pressure characteristics of the bottom plate of the stilling pool were studied with drop sill and sudden expansion and the stilling pool were analyzed with drop sill and sudden expansion (β=1.3,1.6) and the non-sudden expansion stilling pool(β=1.0).The research results of the amplitude characteristics,correlation characteristics,and frequency characteristics of the fluctuating pressure of the bottom plate of the stilling pool can provide a reference and guidance for engineering design. It was found that under different hydraulic conditions,the fluctuating pressure coefficient of the midline of the bottom of the suddenly and non-suddenly expanded stilling pools showed a trend of attenuation along the way,the peak appeared at the head of the stilling pool,and the fluctuating pressure coefficient increased with the increase of the flow energy ratio.Compared with the non-sudden expansion stilling pool,the stilling pool with drop sill and sudden expansion can significantly reduce the fluctuating pressure level of the bottom plate.The probability density of fluctuating pressure in the impingement zone and the wall jet zone conforms to the normal distribution.Under the conditions of different flow energy ratios,the spatial integration scale distribution law of the fluctuating pressure of the bottom of the sudden expansion stilling pool was the same,and all increased along the flow direction,and the spatial integration scale and the fluctuating pressure energy of the sudden expansion stilling pool were significantly lower than that of the non-sudden expansion stilling pool. Under the same hydraulic conditions,the central line fluctuating pressure coefficient of the stilling pool with drop sill and sudden expansion was the same as the non-sudden expansion-type distribution law,and the maximum value of the fluctuating pressure coefficient appeared at the head of the pool.It decayed gradually along the way,and the stilling pool with drop sill and sudden expansion decayed more rapidly.Compared with the non-sudden expansion stilling pool,the sudden expansion stilling pool can significantly reduce the fluctuating pressure level of the bottom plate.The maximum value of the sudden expansion ratio of 1.3 is reduced by 63%,and the maximum value of the sudden expansion ratio of 1.6 is reduced by 42%.The probability density of the fluctuating pressure of the sudden expansion stilling pool conforms to the normal distribution.In the impact area,the spatial integral scale of the sudden expansion type stilling pool was significantly lower than that of the non-sudden expansion type.Its vortex retention was low,accompanied by the continuous generation and fragmentation of the vortex.The predominant frequency of the fluctuating pressure of the sudden expansion stilling pool shifted to high frequency,from 4 Hz to 8 Hz,the possibility of pressure pulsation causing the bottom plate to resonate was very small.However,there was the possibility of resonance in the drop and sudden expansion parts,which should be paid attention.In the engineering design,the relationship between the strength of the fluctuating pressure and the dominant frequency should be comprehensively considered.Under the premise of no resonance,it was beneficial to the project to appropriately reduce the fluctuating pressure.
2021, 19(5):1014-1,023.
Abstract:
In recent years,many scholars worked on river leakage calculation methods.However,the large-scale infiltration test for the pre-construction of underground reservoirs in the ancient river area of China is still lacking.The Suoluhe River is taken as an example for large-scale river infiltration test,and the water balance method is applied to calculate the infiltration capacity to study the mechanism of the response of groundwater level to infiltration capacity to provide a certain scientific basis and reference for the construction of underground reservoirs in ancient river areas. The water balance method was adopted for calculating the river water storage by taking the total recharge water minus the total discharge. Evaluation of river infiltration capacity:Initial stage of infiltration under unstable moving water conditions,the stable infiltration capacity is 0.06 m/d;Infiltration stage under still water condition Ⅰ,the stable infiltration capacity is 0.11 m/d;Infiltration stage under stable moving water conditions,the stable infiltration capacity is 0.13 m/d;Infiltration stage under still water condition Ⅱ,the stable infiltration capacity is 0.08 m/d.Lag mechanism of groundwater level′s response time:Initial stage of infiltration under unstable moving water conditions,the response time of the water level is two days behind;Infiltration stage under still water condition Ⅰ,the response time of the water level is one day behind;Infiltration stage under stable moving water condition,the response time of the water level is one day behind;Infiltration stage under still water condition Ⅱ,the response time of the water level is one day behind;Response mechanism of groundwater level:Initial stage of infiltration under unstable moving water conditions,the stable infiltration capacity is 0.06 m/d,the average daily variation of groundwater level is 0.41 m;Infiltration stage under still water condition Ⅰ,the stable infiltration capacity is 0.11 m/d;the average daily variation of groundwater level is 0.19 m;Infiltration stage under stable moving water conditions,the stable infiltration capacity is 0.13 m/d,the average daily variation of groundwater level is 0.09 m;Infiltration stage under still water condition Ⅱ,the stable infiltration capacity is 0.08 m/d,the average daily variation of groundwater level is 0.02 m.With the extension of infiltration time,the response lag time of groundwater level is shortened,and the increased speed of groundwater level is slowed down. A series of important hydrogeological parameters for the preliminary construction of underground water reservoir are obtained in Suoluhe River.Enriching the research theory of underground reservoirs,and promoting the construction of underground reservoirs in ancient river areas,it has important reference significance for other similar ancient river areas to regulate,store and utilize external water transfer.The deficiency of this study is that the study on the dispersion and diffusion of the groundwater mound is not enough.
In recent years,many scholars worked on river leakage calculation methods.However,the large-scale infiltration test for the pre-construction of underground reservoirs in the ancient river area of China is still lacking.The Suoluhe River is taken as an example for large-scale river infiltration test,and the water balance method is applied to calculate the infiltration capacity to study the mechanism of the response of groundwater level to infiltration capacity to provide a certain scientific basis and reference for the construction of underground reservoirs in ancient river areas. The water balance method was adopted for calculating the river water storage by taking the total recharge water minus the total discharge. Evaluation of river infiltration capacity:Initial stage of infiltration under unstable moving water conditions,the stable infiltration capacity is 0.06 m/d;Infiltration stage under still water condition Ⅰ,the stable infiltration capacity is 0.11 m/d;Infiltration stage under stable moving water conditions,the stable infiltration capacity is 0.13 m/d;Infiltration stage under still water condition Ⅱ,the stable infiltration capacity is 0.08 m/d.Lag mechanism of groundwater level′s response time:Initial stage of infiltration under unstable moving water conditions,the response time of the water level is two days behind;Infiltration stage under still water condition Ⅰ,the response time of the water level is one day behind;Infiltration stage under stable moving water condition,the response time of the water level is one day behind;Infiltration stage under still water condition Ⅱ,the response time of the water level is one day behind;Response mechanism of groundwater level:Initial stage of infiltration under unstable moving water conditions,the stable infiltration capacity is 0.06 m/d,the average daily variation of groundwater level is 0.41 m;Infiltration stage under still water condition Ⅰ,the stable infiltration capacity is 0.11 m/d;the average daily variation of groundwater level is 0.19 m;Infiltration stage under stable moving water conditions,the stable infiltration capacity is 0.13 m/d,the average daily variation of groundwater level is 0.09 m;Infiltration stage under still water condition Ⅱ,the stable infiltration capacity is 0.08 m/d,the average daily variation of groundwater level is 0.02 m.With the extension of infiltration time,the response lag time of groundwater level is shortened,and the increased speed of groundwater level is slowed down. A series of important hydrogeological parameters for the preliminary construction of underground water reservoir are obtained in Suoluhe River.Enriching the research theory of underground reservoirs,and promoting the construction of underground reservoirs in ancient river areas,it has important reference significance for other similar ancient river areas to regulate,store and utilize external water transfer.The deficiency of this study is that the study on the dispersion and diffusion of the groundwater mound is not enough.
2021, 19(5):1024-1031,1040.
Abstract:
The seismic intensity of the area is adjusted from Ⅶ to Ⅷ where the Weihe River barrage project is located.To ensure the safe operation of the Weihe River barrage project,it is necessary to carry out seismic safety review research on the project.At present,most scholars use the quasi-static method to check the seismic calculation of the sluice structure.The sluice belongs to a complex three-dimensional space structure,and the calculation is simplified only according to the conventional plane method,so the calculation result has a large error.In recent years,with the rapid development of computer technology,finite element numerical simulation technology has been widely used in the seismic analysis of sluices,but how to evaluate the safety of the area where the tensile stress exceeds the tensile strength of concrete is less studied. Given the problems existing in the seismic safety review of sluice structure,based on the finite element numerical simulation technology and ADINA finite element analysis software,an analysis method combining finite element numerical simulation and structural mechanics calculation was proposed.This method could effectively make up for the shortcomings caused by the simple use of finite element numerical simulation and could provide the corresponding basis and reference for the similar sluice seismic safety review. Taking the Weihe River sluice as an example,a three-dimensional finite element model of the sluice was established.The seismic response of the sluice chamber was calculated and analyzed by the mode decomposition response spectrum method,and the seismic safety evaluation of the sluice was carried out.Among them,for the area where the tensile stress exceeds the tensile strength of concrete in the finite element,combined with the actual reinforcement amount of the part,according to the flexural capacity of the normal section,the maximum bending moment of the section in the area where the stress exceeds the limit was obtained.The maximum bending moment on the section was deduced according to the calculation formula of normal stress of flexural members.Finally,the area where the tensile stress exceeded the tensile strength of concrete could be rechecked by comparing the calculated normal stress results with the finite element stress calculation results.In addition,based on the finite element calculation results of each node of the bottom plate of the lock chamber,the antisliding stability of the lock chamber structure could be calculated. The first five vibration modes of sluice chamber structure were mainly reflected in the vibration of beam and frame bridge structure.The results show that the fundamental frequency of natural vibration was 6.33 Hz under the condition of no water and normal water storage,and the natural frequency did not decrease obviously after considering the effect of hydrodynamic pressure.Under the earthquake action of normal water storage condition,large tensile stress appeared at the joint of side hole beam and frame bridge and the joint of frame bridge and pier,and its maximum tensile stress exceeded the standard value of dynamic tensile strength of concrete,but considering the local reinforcement,the tensile stress met the safety demand.Simultaneously,large compressive stress appeared at the corner of the frame bridge and other geometric mutation,and the maximum compressive stress did not exceed the standard value of concrete dynamic compressive strength,which met the safety requirements.Under the most unfavorable seismic condition,the safety factor of the anti-sliding stability of the whole sluice chamber was 1.68,which met the safety requirements. According to the Guidelines for Sluice Safety Evaluation (SL 214—2015),the seismic safety of the sluice met the standard requirements,and its seismic grade was Grade A.
The seismic intensity of the area is adjusted from Ⅶ to Ⅷ where the Weihe River barrage project is located.To ensure the safe operation of the Weihe River barrage project,it is necessary to carry out seismic safety review research on the project.At present,most scholars use the quasi-static method to check the seismic calculation of the sluice structure.The sluice belongs to a complex three-dimensional space structure,and the calculation is simplified only according to the conventional plane method,so the calculation result has a large error.In recent years,with the rapid development of computer technology,finite element numerical simulation technology has been widely used in the seismic analysis of sluices,but how to evaluate the safety of the area where the tensile stress exceeds the tensile strength of concrete is less studied. Given the problems existing in the seismic safety review of sluice structure,based on the finite element numerical simulation technology and ADINA finite element analysis software,an analysis method combining finite element numerical simulation and structural mechanics calculation was proposed.This method could effectively make up for the shortcomings caused by the simple use of finite element numerical simulation and could provide the corresponding basis and reference for the similar sluice seismic safety review. Taking the Weihe River sluice as an example,a three-dimensional finite element model of the sluice was established.The seismic response of the sluice chamber was calculated and analyzed by the mode decomposition response spectrum method,and the seismic safety evaluation of the sluice was carried out.Among them,for the area where the tensile stress exceeds the tensile strength of concrete in the finite element,combined with the actual reinforcement amount of the part,according to the flexural capacity of the normal section,the maximum bending moment of the section in the area where the stress exceeds the limit was obtained.The maximum bending moment on the section was deduced according to the calculation formula of normal stress of flexural members.Finally,the area where the tensile stress exceeded the tensile strength of concrete could be rechecked by comparing the calculated normal stress results with the finite element stress calculation results.In addition,based on the finite element calculation results of each node of the bottom plate of the lock chamber,the antisliding stability of the lock chamber structure could be calculated. The first five vibration modes of sluice chamber structure were mainly reflected in the vibration of beam and frame bridge structure.The results show that the fundamental frequency of natural vibration was 6.33 Hz under the condition of no water and normal water storage,and the natural frequency did not decrease obviously after considering the effect of hydrodynamic pressure.Under the earthquake action of normal water storage condition,large tensile stress appeared at the joint of side hole beam and frame bridge and the joint of frame bridge and pier,and its maximum tensile stress exceeded the standard value of dynamic tensile strength of concrete,but considering the local reinforcement,the tensile stress met the safety demand.Simultaneously,large compressive stress appeared at the corner of the frame bridge and other geometric mutation,and the maximum compressive stress did not exceed the standard value of concrete dynamic compressive strength,which met the safety requirements.Under the most unfavorable seismic condition,the safety factor of the anti-sliding stability of the whole sluice chamber was 1.68,which met the safety requirements. According to the Guidelines for Sluice Safety Evaluation (SL 214—2015),the seismic safety of the sluice met the standard requirements,and its seismic grade was Grade A.
2021, 19(5):1032-1040.
Abstract:
Water,environment,and ecology problems brought by the construction of hydropower plants are getting more and more attention.Water temperature is one of the most important influencing factors for water environment assessment.Water temperature plays an important role in the physical,chemical and biological processes in aquatic systems,and is a fundamental element of water environment research,with a very wide range of influence.Large reservoirs after storage,easy to form water temperature stratification,the temperature difference between the surface and bottom layer can be as high as 20 ℃.Most of the completed reservoirs have low intake locations and are not easy to change,resulting in low-temperature water released,which in turn causes serious environmental impacts on the reservoir area and downstream.The most direct harm of low-temperature water released is to reduce crop yields,delay the spawning period of fish.Water temperature stratification causes stratification of water quality parameters,resulting in water quality deterioration,which harms water ecology.Reservoir low-temperature water released has become a hot issue in the current research.In this regard,it is necessary to adopt a series of engineering measures to improve the negative impact caused by the low-temperature water released. Taking Dongqing reservoir as an example,a three-dimensional water temperature-hydrodynamic mathematical model was constructed to simulate the temperature of water released from the reservoir and the water temperature distribution in front of the dam under different retaining wall elevation,and to analyze the variation law between the front retaining wall elevation and the temperature of water released and water temperature in front of the dam. The results show that the improvement effect of the released temperature is closely related to the retaining wall elevation.When the retaining wall was lower than the intake,the change of the retaining wall elevation has almost no effect on the released temperature.When the retaining wall was higher than the intake by a certain height,the higher the retaining wall elevation is,and higher the released temperature.When the retaining wall elevation is 480 m,the maximum increase of the released temperature in April is 1.11 ℃.The increase of the released temperature is linearly related to the difference of the vertical water temperature in front of the dam corresponding to the location of the retaining wall and the water intake.The vertical water temperature distribution in front of the dam is also affected by the retaining wall,when the elevation of the retaining wall is higher than the water intake elevation by a certain height,as the elevation of the retaining wall increases,the thickness of the thermocline increases and the position rises.The relationship between the improvement effect of the released temperature and the height of the retaining wall is more complicated,and the location of the faster growth of the released temperature increase occurs at the retaining wall elevation of 471 m and 475 m. The front retaining wall can be used to improve the negative impact on the environment caused by the low temperature of water released.When the retaining wall elevation is lower than the intake elevation,the change of retaining wall elevation has almost no effect on the temperature of the water released from the reservoir.When the retaining wall elevation is higher than the water intake elevation by a certain height,the retaining wall elevation determines the temperature of water released,with the increase of the retaining wall elevation,the temperature of the water released from March to June increases,the higher the retaining wall elevation,the more obvious the improvement effect.When the retaining wall elevation is lower than the water intake elevation,the water temperature distribution in front of the dam is not affected by the retaining wall.When the top elevation of the former retaining wall is higher than the water intake elevation by a certain height,with the increase of the retaining wall elevation,more surface high temperature water is released,and the temperature leap layer position rises,and the thickness increases.The increase of the retaining wall elevation weakens the vertical heat exchange of the bottom water body in front of the dam.When the retaining wall elevation is higher than the water intake elevation by a certain height,the degree of improvement of the water temperature released by the retaining wall is related to the difference in the vertical water temperature between the retaining wall and the water intake elevation,the larger the difference,the greater the degree of improvement of the lower released water temperature,and there is a linear correlation.Analyzing the encrypted calculation scheme,there are two extreme points for the growth rate of the lower released water temperature increase,and the growth rate of the increase is greatest at the height of the retaining wall 475 m and 471 m.Considering the engineering feasibility,the top elevation of the retaining wall is set to 471 m as the optimal choice.
Water,environment,and ecology problems brought by the construction of hydropower plants are getting more and more attention.Water temperature is one of the most important influencing factors for water environment assessment.Water temperature plays an important role in the physical,chemical and biological processes in aquatic systems,and is a fundamental element of water environment research,with a very wide range of influence.Large reservoirs after storage,easy to form water temperature stratification,the temperature difference between the surface and bottom layer can be as high as 20 ℃.Most of the completed reservoirs have low intake locations and are not easy to change,resulting in low-temperature water released,which in turn causes serious environmental impacts on the reservoir area and downstream.The most direct harm of low-temperature water released is to reduce crop yields,delay the spawning period of fish.Water temperature stratification causes stratification of water quality parameters,resulting in water quality deterioration,which harms water ecology.Reservoir low-temperature water released has become a hot issue in the current research.In this regard,it is necessary to adopt a series of engineering measures to improve the negative impact caused by the low-temperature water released. Taking Dongqing reservoir as an example,a three-dimensional water temperature-hydrodynamic mathematical model was constructed to simulate the temperature of water released from the reservoir and the water temperature distribution in front of the dam under different retaining wall elevation,and to analyze the variation law between the front retaining wall elevation and the temperature of water released and water temperature in front of the dam. The results show that the improvement effect of the released temperature is closely related to the retaining wall elevation.When the retaining wall was lower than the intake,the change of the retaining wall elevation has almost no effect on the released temperature.When the retaining wall was higher than the intake by a certain height,the higher the retaining wall elevation is,and higher the released temperature.When the retaining wall elevation is 480 m,the maximum increase of the released temperature in April is 1.11 ℃.The increase of the released temperature is linearly related to the difference of the vertical water temperature in front of the dam corresponding to the location of the retaining wall and the water intake.The vertical water temperature distribution in front of the dam is also affected by the retaining wall,when the elevation of the retaining wall is higher than the water intake elevation by a certain height,as the elevation of the retaining wall increases,the thickness of the thermocline increases and the position rises.The relationship between the improvement effect of the released temperature and the height of the retaining wall is more complicated,and the location of the faster growth of the released temperature increase occurs at the retaining wall elevation of 471 m and 475 m. The front retaining wall can be used to improve the negative impact on the environment caused by the low temperature of water released.When the retaining wall elevation is lower than the intake elevation,the change of retaining wall elevation has almost no effect on the temperature of the water released from the reservoir.When the retaining wall elevation is higher than the water intake elevation by a certain height,the retaining wall elevation determines the temperature of water released,with the increase of the retaining wall elevation,the temperature of the water released from March to June increases,the higher the retaining wall elevation,the more obvious the improvement effect.When the retaining wall elevation is lower than the water intake elevation,the water temperature distribution in front of the dam is not affected by the retaining wall.When the top elevation of the former retaining wall is higher than the water intake elevation by a certain height,with the increase of the retaining wall elevation,more surface high temperature water is released,and the temperature leap layer position rises,and the thickness increases.The increase of the retaining wall elevation weakens the vertical heat exchange of the bottom water body in front of the dam.When the retaining wall elevation is higher than the water intake elevation by a certain height,the degree of improvement of the water temperature released by the retaining wall is related to the difference in the vertical water temperature between the retaining wall and the water intake elevation,the larger the difference,the greater the degree of improvement of the lower released water temperature,and there is a linear correlation.Analyzing the encrypted calculation scheme,there are two extreme points for the growth rate of the lower released water temperature increase,and the growth rate of the increase is greatest at the height of the retaining wall 475 m and 471 m.Considering the engineering feasibility,the top elevation of the retaining wall is set to 471 m as the optimal choice.
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