Characteristics and attribution of groundwater depth changes in Jinan City
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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.
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