The Study On The Ecological Water Requirement And Ecological Operation In The Lower Reaches Of Heihe River For Ecological Conservation And Restoration

Water resources is one of the most active factor in the overall environment,whose amount decides whether human's living place and the biosphere could maintain a benign development.Especially in arid regions,water resources has totally become the bottleneck restricting local ecological construction and social economic progress.For example,the Heihe River basin located in northern west China is typically an area that short of water,whose downstream ecological degradation has not only decreased the stability of aggregate ecosystem but made the whole ecological security in north China in peril.Therefore,for its ecological conservation,it is necessary to analyze and study the water demand and scheduling plan of lower reaches of Heihe River basin by optimizing its quantity allocation scheme.Based on an objective of ecological protection and restoration of the lower reaches of Heihe River,this article adopts diving evaporation transpiration model to calculate the amount of water consumed by natural vegetation and evaporation of rivers and lakes.Besides,according to groundwater balance equation,ecological water recovery amount could be calculated,so do that of the lower reaches of Heihe River.Moreover,by referring to the previous research findings of groundwater flow field and depth distribution of each ecological region in oasis core area that computed by existing groundwater simulation model,the overall status and water shortage degree in pro-phase irrigation would stand to reason.At last,by resorting to the main vegetation types and scale,this paper would provide a suitable depth of groundwater level for each ecological region and work out an appropriate allocation through several times simulations.In the mid-1980,vegetation in the lower reaches of Heihe River grew well,its average depth of groundwater was 2.75 m;due to the decrease of released water of Zhengyixia reservoir,average groundwater depth has reduced to 3.28 m until 2012,as well as natural vegetation area and vegetation coverage are reduced.Groundwater depth should be increased at least 0.5 m to achieve the level in the 80s,and based on the formula to calculate,there will need 0.44 million m3 of groundwater recharge very year.According to scheme of the State Council for water diversion,multi-year average released water of Zhengyixia reservoir is 950 million m3.The multi-year average released water from upstream to Shaomaying section is 635 million m3 by simulated calculating.Under the condition of water distribution,according to ecological restore targets,average groundwater depth will be recovered to 2.78 m before 2020,the quantity of groundwater recharge for recovering should be 0.44 million T13.Underground water level comes to a steady state thereafter.The groundwater depth in 2030 will keep the 2020 level.With no regard for intake water of the East Juyan lake,the minimum ecological wate-r distribution of Shaomaying is 2.39 million m3 and water distribution of Shaomaying in actuality year is 5.47 million m3.In order to achieving the targets of ecological co nservative and restoration,ecological water distribution of Shaomaying will be 6.35 mill ion m3;The minimum ecological water distribution of Langxinshan in the low-flow ye ar is 1.99 million m3 and water distribution of Langxinshan in actuality year is 4.77m illion m3,ecological water distribution of Langxinshan will be 5.17 million m3 and 5.32 million m3 in 2020 and 2030 respectively.