Streamflow and sediment characteristics of Ejina River under ecological water transportation
- Article
- Figures
- Metrics
- Preview PDF
- Reference
- Related
- Cited by
- Materials
Abstract:
Ejina oasis is located in Alxa Ejina Banner in the western Inner Mongolia Autonomous Region of China. As the first line of ecological defense in north and northwest China, Ejina oasis plays an important role in the economic and social development of north and northwest China, despite its fragile ecological environment. In the latter half of the 20th century, due to the excessive exploitation and utilization of the middle and upper reaches of the Heihe River, the flowing period of the Ejina River was greatly shortened, while the degradation of vegetation and ecosystem of Ejina oasis was accompanied by the severe sandstorms in north China. In order to contain the further ecological deterioration of the lower reaches of Heihe River, the ecological water transfer project was implemented in 2000, since the man-made intermittent water transfer significantly alleviated the ecological deterioration trend of Ejina oasis. Sediment and pollutants flow into the East Juyan Lake along with the runoff, resulting in sedimentation, water quality deterioration and evaporation increasement. Therefore, the analysis of the variation characteristics of streamflow and sediment in the Ejina River is one of the important contents of oasis ecological protection and water distribution management.According to the characteristics of water transport in Ejina oasis, a year is divided into three periods: dry period (no water flow), water transport period (no sand flow) and sediment transport period (sand flow). Based on the daily surface runoff data from 1988 to 2020 and the daily river sediment data from 2006 to 2020 observed at the Donghe and Xihe River sections of Langxin Mountain Hydrological Station, the annual and interannual changes of runoff and sediment in different periods were analyzed by comparative analysis, regression analysis and mathematical statistics. The discharge of Ejina River has obvious seasonal variation, as well the discharge in summer and autumn is significantly higher than that in spring and winter. While the average discharge in spring, summer and winter was still lower than the average level before ecological water transport, the runoff in autumn recovered well and reached nearly 400 million m3 in 2020. The duration of water transport period is characterized by short summer and long winter. Except for summer, the duration of water transport period in all seasons is lengthened. The annual average runoff of Ejina Donghe River is significantly higher than that of Ejina Xihe River, accounting for 72% of the total runoff of Ejina River, which exceeds the statistical data from 2000 to 2015 (70%). After the ecological water transfer in 2000, the runoff volume of Ejina River changed from a sharp downward trend to a significant upward trend. By 2020, the average annual discharge of Ejina Donghe River and Xihe Rivers has reached 16.9 m3 /s and 9.7 m3/s respectively, which is close to the level in the late 1980s. Stage in addition, the water transport period and the sediment transport period of Ejina River are consistent, while the increase of sediment discharge is still affected by the increase of runoff. The maximum sediment concentration generally occurs in July and August when the flow is high, while the sediment discharge in summer and autumn accounts for more than 90% of the whole year. The sudden increase of discharge is a necessary condition for the formation of the strong sediment transport event in the Ejina Donghe and Xihe Rivers, while it is also restricted by the size of discharge and the times of water transport. Generally, only when the peak flow rate increases sharply to more than 100 m3/s for the first time, high sediment concentration (> 5 kg/m3) events will occur, while the sediment content of the river will also decrease with the decrease of the discharge. The relationship between river sediment concentration and river discharge is significant nonlinear. In summer and autumn, the discharge is high, accompanied by strong sediment transport (sediment concentration > 5 kg/m3) and medium sediment transport event (sediment concentration > 1 kg/m3), while the river discharge in spring and winter is small, and most of them are weak sediment transport events(< 1 kg/m3).
Keywords:
Project Supported:
Clc Number:
Mobile website
® 2024 All Rights Reserved
冀公网安备13010502002656号
冀公网安备13010502002656号