The Watershed Ecological Water Demand Researh Based On The Distributed Hydrological Model

Inter-basin water diversion projects greatly impact the hydrological regime and ecological system of water source area,how to quantitatively evaluate the impact,is the key to guarantee the health of the watershed ecosystem.This study tried to reveal a feedback effect between the hydrological cycle and ecological system through the distributed watershed ecological water demand research.(1)Research on runoff process forecasting.The daily rainfall-runoff data of Hanjiang River Basin from 2000 to 2012 have been collected.The MIKE SHE model has been established based on the basic data of Hanjiang River Basin.2/3 of the data were used for model calibration while the remaining data were for model verification.The results show that the Nash efficiency coefficient of the runoff process is about 0.73,and the water balance coefficient is about 0.85 for the parameter rate and the parameter test period.(2)Calculation of ecological water demand outside the river.In this paper,the ecological water demand of river basin is divided into ecological water demand and ecological water demand outside the river.The ecological water demand outside the river is evaluated by MIKE SHE output data.The results show that between 2000 and 2012,The spatial distribution of water demand is basically the same,and the area with satisfaction greater than 0 is mainly concentrated in the upper reaches of the Hanjiang River.The area with satisfaction less than 0 is mainly concentrated in the middle and lower reaches of the Hanjiang River.The area of the area with the satisfaction degree greater than 0 has a significant increase,and the increase of the upper reaches of the Hanjiang River is far greater than that in the middle and lower reaches of the Hanjiang River.(3)Calculation of ecological water demand intside the river.The Range of Variability Approach is used to quantitatively estimate the temporal and spatial variation of the hydrologic regime in the mainstream of the Hanjiang River after the impoundment of the Danjiangkou Reservoir.The results show the highest Indicators of Hydrology Alteration(IHA)in different stations and IHA groups,as well as the corresponding ecological impacts.It is demonstrated that the degree of discharge alteration in the lower reaches of Hanjiang River is rather moderate(range from 47%to 63%),the degree of water surface elevation alteration is rather high,Xiang Yang and HuangZhuang have highest alteration of water surface elevation(proportion is 53%and 75%).More specifically,the water surface elevation decreased significantly at all stations(decreased 1-2 m).The frequency and duration of high/low flow pulses in Huangjiagang station of decreased(IHA is-0.49/-0.62 and-0.87/-0.74).The monthly mean and extreme values of discharge and water surface elevation at Huangzhuang and Xiangyang stations decreased,the frequency of discharge reversal magnitude increased(IHA is 1.82 in high RVA range).The occurrence of those Indicators that captured the effects of IHA on the four major Chinese carps was less frequent during the post-dam construction period compared to that before the impoundment.The discharge and water surface elevation of the lower reaches decreased during the dry season,thus increasing the possibility of water bloom occurrence.