Law Of Change About Runoff And Sediment In The Jinghe River And Effects Of Change On The Jing Huiqu Irrigation Area

Under the influence of global climate change and increasing human activities,the hydrological cycle of the basin has changed to some extent.From the simple natural water exchange relationship in the past to the complex relationship of human activities.This issue has attracted widespread attention of scholars at home and abroad.However,the uncertainty of climate change and the complexity of human activities,the mechanism of response to the runoff and sediment processes in the basin is still unclear,relevant scientific issues need to be further studied.In this paper,the significant differences in runoff and sediment changes in the Jinghe River Basin in recent years are studied.Through data analysis,the development and evolution of runoff and sediment processes,human activities and climate change in the study basin over the past few decades are deeply explored and distributed,and based on the Hydrological model,quantitative analysis of the impact of land use and climate change on the runoff and sediment process in the basin,and finally the systematic discussion and research on the status of surface water resources utilization in the downstream JingHuiqu Irrigation District,aiming at the Jinghe River The impact of runoff and sediment changes in the basin on the downstream irrigation area is comprehensively analyzed.The main research contents and conclusions are as follows:(1)In the flood season,runoff and sediment occupy 69.79%and 97.15%of the year.The interannual fluctuations are mainly based on the 2-year cycle;the inter-monthly fluctuations are mainly dominated by the 12-month cycle,and the variation law is strongly influenced by the annual climatic conditions.Under the influence of returning farmland to forest project and human water and sediment regulation,the annual average of runoff and sediment decreased from 13.38×10~8m~3 and 2.34×10~8t to 10.21×10~8m~3 and 1.17×10~8t,and the mutation occurred in 1996.After the mutation,the probability of synchronization of runoff and sediment decreased,and the probability of asynchronous over 50%.(2)The climatic factors in the Jinghe River Basin are generally unevenly distributed during the year,and the multi-year change trend of climate factors varies greatly from month to month.In terms of interannual variation,except for the rising temperature of many years,other climatic factors have shown a downward trend for many years.The insignificant downward trend of rainfall for many years indicates that the rainfall factor is not the main reason for the significant decrease in runoff.Cultivated land and grassland are the main types of land use in the Jinghe River Basin,accounting for about 88%.Due to the vigorous development of returning farmland to forests and grasslands and urbanization,the area of cultivated land has decreased by 407 km~2 over the years,and the area of forest land and human land has increased by 248 km~2 and 164 km~2,respectively.(3)Runoff is greatly affected by climate change,and vegetation cover type has a stronger correlation with sediment erosion.Among the land use types,the change of the area of cultivated land,grassland and forest land has a significant impact on the runoff and sediment change in the basin.According to the attribution study of the sediment reduction in the Jinghe River,the contribution of climate and land use change only accounted for 25.20%and 17.16%;while the water consumption in the upstream area increased by 2.12×10~8m~3 for many years and the excellent sand-blocking effect of the silt dam indicates runoff and sediment.The reduction is more due to the direct water grabbing activities of humans in the upper reaches.(4)The water resource availability of the river channel in the headwater of the JingHuiqu irrigation area decreased from 6.19~7.26×10~8m~3 to 5.54~6.62×10~8m~3,while the river water resource utilization rate increased from 46.05~54.01%to 54.26~64.83%.Under the premise that the water diversion capacity of the canal project in the irrigation area has also been greatly extended,there is still a potential water volume of 1.16~1.40×10~8m~3.Due to the limited capacity of controlled irrigation projects in irrigation districts and the lack of matching of canal systems,the irrigation water diversion utilization rate of irrigation heads is low,and the imbalance of water supply and demand in irrigation districts becomes more and more prominent.By digging the water diversion potential of the head,improving the effective irrigation rate and irrigation methods,the contradiction between water supply and demand in the irrigation area can be obviously alleviated.