Water Resources Regulation In The Heihe River Basin By Using An Integrated Surface Water-ground Water Modeling Approach

Heihe River Basin(HRB)is one of endorheic river basins in the arid area of China.Its middle-stream part is an important grain production base in China and consumes tons of water resources.There is a series of ecological problems in HRB as a result of overexploitation of water resources.Thus,it is of great importance for local authorities to reasonably manage water resource.Besides,climate change recently has led to such regional extreme catastrophes as droughts and floods,making future water resource management harder.To tackle these two challenges,this study developed optimal allocation model of water resource with conjunctive use of groundwater and surface water.The optimization objective is to maximize economic benefit of irrigation zone at middle HRB.The optimization model was solved by simplex algorithm.The simulation of water resources regulation in middle and lower HRB(ML-HRB)from 2000 to 2016 was carried out by the optimal allocation model.By making use of the optimization model,water supply rates in irrigation zones go rise.Additionally,this study combined Principal Components Analysis(PCA)and Long Short-term Memory(LSTM)to predict daily mountainous runoff in the upper HRB.PCA simplifies the structure of LSTM and improves the simulation performance.The LSTM model enables to predict long-term streamflow merely using only meteorological driving forces.According to the prediction results,the mountainous runoff from 2017-2060 drops by a rate of 1.0×106 m3/yr.Finally,optimal allocation model was used to research water cycle in middle and lower HRB under future climate change scenario.The simulation result shows that future evapotranspiration(ET)in ML-HRB will decrease by-0.07mm/yr,while future ET in irrigation zones will rise.Future streamflow through Zhengyixia will decline by 5.5×105m3/yr.The irrigation zones closer to upper HRB will get more water resource.