Study On Sustainable Utilization Of Water Resources In An Arid Inland Basin Under Conditions Of Climate Change

The water resources are scarce and the ecological environment is fragile in arid and semiarid areas of northwest China.Both of them are more sensitive to global climate change.It is of great theoretical and practical significance to study the sustainable utilization of water resources in arid areas under the conditions of climate change,and helps to construct the life community of mountain,water,forest,field,lake and grass,and helps to realize the harmonious symbiosis between human and nature.The middle reaches basin of the Heihe River mainstream of the Heihe River Basin(HRB),which is the second largest arid inland river basin in China,is chosen as the study area in this paper.Based on the latest data,the paper sums up the law of water infiltration and groundwater overflow in the mainstream of Heihe River,and obtains a new understanding of the transformation between the river water and groundwater.A new groundwater flow numerical model of the middle reaches basin is established,and the temporal and spatial distributions of both groundwater flow and groundwater velocity are described in detail,revealing that the change of natural conditions is the main reason for the change of groundwater resources.This paper predicts water resources change in multi scenarios in the next 20 years,and puts forward the sustainable utilization optimization schemes of regional groundwater resources.The main results obtained in this paper are as follows:(1)In aspect of the mutual transformation relations between the river water and groundwater,the control sectional empirical function between water infiltration and water inflow for the reach of Caotanzhuang-G312 Bridge is summed up based on the G312 Bridge flow measuring data,and the infiltration amount of this reach is calculated as 4.71×10~8 m~3/a from 1990 to 2013 according to function.Based on the method of river water budget,the river water infiltration amount of the Yingluoxia-Caotanzhuang reach is calculated as 2.03×10~8 m~3/a,and the groundwater overflow of the G312 Bridge-Zhengyixia reach is calculated as 12.51×10~8 m~3/a from1990 to 2013.(2)In aspect of groundwater system,the heterogeneous and anisotropic three-dimensional transient flow numerical model of the middle reaches basin of the Heihe mainstream is established,which determines both the main flow area and the high velocity area of the basin.The groundwater budge of the basin is in negative equilibrium state from 1990 to 2013 overall,-1.090×10~8 m~3/a on average annually,and the negative budget state improves significantly after the year 2000,after which the HRB tends to be more abundant in water resources.Groundwater recharge amounts of the basin are calculated under conditions of average Yingluoxia runoff and runoffs of 4 typical guarantee rates according to the numerical model.The natural conditions and human activities of groundwater recharge and discharge are quantitatively identified by setting up situation of water resources allocation in the middle reaches basin.The strong mutual transformation between surface water and groundwater is a typical water resources characteristic in the HRB.(3)Future water resources change scenarios are proposed based on historical recurrence method and CMIP5 climate model prediction method respectively.The teleconnections between meteorological elements of the HRB and multiple global climatic indices are analyzed.The predictions of future precipitation and potential evapotranspiration in the HRB are applied to the predictions of the future Yingluoxia runoffs,and the precipitation and land surface evapotranspiration of the middle reaches basin.(4)In aspect of optimal utilization of water resources,the future water diversion quantity,the amount of exploitation and the infiltration amount of the river water are provided for the analysis of water resources,based on the target programming model in multi future scenarios.(5)The sustainable utilization analysis of the middle reaches basin of the HRB shows that the future development and utilization of water resources is unsustainable in the context of historical recurrence scenario.The negative groundwater budgets improve significantly in the future climate change scenarios.In RCP4.5 pathway of climate change superimposed water saving irrigation scenario,the future groundwater of the basin is in state of positive budget overall,and the Zhengyixia runoffs can meet the requirements of the State Council's water supply scheme in much more years in the future.Water-saving irrigation is an important measure to realize the sustainable utilization of water resources in the HRB.