Research On The Balance And Optimal Allocation Of Water Resources In The Heihe River Basin Based On Water Supply And Service Flow

Heihe River Basin is located in the core area of China Silk Road Economic Belt and is also a key area in the strategic pattern of ecological security.The basin is characterized by drought,less precipitation and serious shortage of water resources.Under the influence of climate change and rapid development of social economy,the contradiction between water supply and demand is becoming more and more prominent,and ecological environment problems have appeared in the upper and middle reaches and lower reaches.Human activities and ecosystems in the basin depend on the support of runoff water resources.Scientific and reasonable evaluation of the water resources supply and demand in the region,rational development and utilization of water resources can effectively alleviate the existing ecological problems and promote the sustainable development of regional social economy.Traditional water resource supply and demand evaluation often ignores the upstream water supply and demand to the downstream water,only from the static point of view to evaluate the relationship between supply and demand of water resources.Based on the water supply service flow model,this study evaluates the dynamic water resources safety status of Heihe River Basin on different scales,and compares with the static evaluation system.In addition,the grey model is used to forecast the future water resource demand,and the spatial pattern of dynamic supply and demand of water resources is simulated according to different water supply scenarios.The multiobjective optimization model of water resource allocation is established based on the dynamic supply and demand balance.The optimal proportion of water demand in different sub basins and different departments in the region is optimized to realize the coordinated development of society,economy and ecology of the basin.The main conclusions of this study are as follows:(1)The water supply volume of the fifth stage of Heihe River Basin from 2000 to 2018 is 22.70×108m3,26.60×108m3,21.15×108m3,20.84×108m3 and 24.35×108m3 respectively,showing the trend of increasing fluctuation;the upper Qilian mountain area is the main production area of the whole basin,and the majority of the areas in the middle and lower reaches have no water production capacity;92.37%of the sub watershed water production capacity is relatively stable from 2000 to 2018,with 7.63%The water production capacity of the sub watershed fluctuates greatly by climate change,and it is mainly located in the upstream region.(2)The demand for water resources in the fifth stage of Heihe River Basin from 2000 to 2018 is 42.41×108m3,45.87×108m3,47.40×108m3,49.99×108m3 and 53.4×108m3 respectively,showing a continuous increase trend;the proportion of agricultural water demand is the highest among the total water demand,accounting for over 91%each year;the oasis agricultural irrigation area in the middle reaches is the main water area of the whole basin,with low water demand in the upstream and downstream areas;2000-In 2018,89.83%of the sub watershed water demand intensity remained relatively stable,9.3%of the sub watershed water demand intensity was significantly increased,and it was mainly located in the middle reaches.(3)The current supply area of the fifth phase water supply service in Heihe River Basin from 2000 to 2018 accounted for 20.80%,20.70%,19.62%,24.71%and 24.74%respectively.Taking 2010 as the turning point,it showed a trend of first falling and rising;under natural conditions,the flow and supply capacity of water supply service in Heihe River Basin was limited,and the overall performance was that the upstream was larger than the middle reaches and the middle reaches were larger than the downstream.(4)The proportion of dynamic water resources safety index greater than 1 and less than-1 in Heihe River Basin increased from 2000 to 2018,and the problem of mismatch between supply and demand of water resources in the region increased.Compared with the static evaluation system,the regions with the characteristics of 0.13%,0.12%,0.12%,0.13%and 0.10%respectively changed from severe water shortage to mild water shortage in 2000,2005,2010,2015 and 2018 respectively,with 0.20%,0.22%,0.14%,0.17%and 0.17%of the regions changed from water shortage to surplus state.On the sub watershed scale,compared with the static evaluation system,the water resource safety level has not changed,and the flow supply is not enough to change the water safety status in the sub watershed.(5)Based on scenario 1 in 2035,when the water production increases by 5%compared with 2018,the current supply area will increase by 2.13%,the water shortage area will decrease by 0.06%,and the surplus area will increase by 0.15%;when the water yield increases by 10%compared with 2018,the current supply area will increase by 2.40%,and the water shortage area will be reduced by 0.15%,and the surplus area will increase by 0.30%;when the water yield is generated Compared with the reduction of 5%in 2018,the current supply area will be reduced by 1.02%,the water shortage area will increase by 0.13%,and the surplus area will be reduced by 0.28%;when the water production is reduced by 10%compared with 2018,the current supply area will be reduced by 16.51%,the water shortage area will increase by 0.24%and the surplus area will be reduced by 0.53%.The water resource safety level of sub watershed under different water supply scenarios in 2035 is relatively stable,and the increase and decrease of water production in 5%to 10%will not change the water safety status of sub watershed.