The Evaluation Of Ecosystem's Health And Service For Dong Ju Yan Hai

Wetland is a unique ecosystem with many functions.It can provide a variety of resources and services and is a basic resource for the development of human society.Dong Ju Yan Hai Wetland is located in Ejina Qi of Alashan League in Inner Mongolia and is known as the“Pearl of Dessert”.However,since the 1950s,with the dramatic increase in water use for industry and agriculture in the Heihe River Basin,the amount of water entering the lake has plummeted,and the Dong Ju Yan Hai Wetland has completely dried up in 1992,becoming one of the major source of sand storm in northwest of China.The problem of deterioration of the ecological environment in Dong Ju Yan Hai has caused the party and the country to attach great importance to it.It was decided to implement the unified management of the Hei he water resources management and the comprehensive management of the river basin,rationally allocate the basin water resources,ensure the ecological water demand of the Dong Ju Yan Hai wetland,and curb its ecological deteriorating trends and gradual restoration of wetland functions.In July 2002,Heihe River was relocated to Dong Ju Yan Hai,which was dried for10 years.At present,the water surface area of Dong Ju Yan Hai is basically maintained at about 40km2.The Dong Ju Yan Hai wetland and its surrounding ecosystems have obviously recovered and improved.Currently,even though some good results have been achieved after the management,the historical evolution process and influence mechanism of Dong Ju Yan Hai is still not clear.At the mean time,it is lack of the evaluation standard for the health status of Dong Ju Yan Hai wetland ecosystem.And the ecological service function and value of Dong Ju Yan Hai Wetland have not been quantified yet.Finally,the basic water quantity that sustains the health of Dong Ju Yan Hai,and the optimal supply of local groundwater resources have not been computed.Based on the remote sensing image data of Dong Ju Yan Hai during different periods,this study investigates the evolution process and mechanism of Dong Ju Yan Hai wetland.Through the construction of indicator system of ecosystem health,the ecological health status have been evaluated between 1990 and 2015.And the value of service function of wetland ecosystem has been computed by implementing the evaluating system of service function value.Through the hydrological survey of Dong Ju Yan Hai and its surrounding areas,this study analyzes the change of wetland water environment and source of ground water supply.Finally,based on related supervising data and models of water demand,this study computes the basic water requirement for the health of wetland ecosystem.Through the above research,we have obtained the following main conclusions:1?Evolution of the Dong ju yan hai in the historical period and the change of landscape pattern in recent 30 yearsSince the 1980s,Dong ju yan hai dried up twice,respectively in 1986 and 1992-2001,and the area of waters in the mid-1980s that was interpreted by remote sensing was about 35 km2.The water area has reached this level since 2005.In the 1980s,the vegetation of Dong ju yan hai was mainly dominated by shrubs and herbs.In the south,it stretched continuously around the east and stretched to form a strip.It was severely degraded since 1992.Till 2001,this area became barren land.After 2002,the water was supplied continuously,the vegetation area increased significantly.Herbs are the most obvious,and vegetation has gradually shifted from degeneration to gradual recovery.2?Ecological diagnosis and assessment of Yanhai Yanhai wetland ecosystemThe Pressure-State-Response(PSR)model was selected to construct the Dongju Yanhai Wetland Ecosystem Health Evaluation Index System.At the mean time,the sample used contains annual data from 1990 to 2015,and the ecosystem health index is calculated.The results show that,the index in1990 is relatively high,but because of drought of Dong Ju Yan Hai,its ecosystem was destroyed completely,then this index decreases.After the water resources management and the corresponding gouvernance,since 2001,this ecosystem became to recover gradually.In 2010,this index is larger the it is in 1990,and continue to increase,which implies that,the health status of Dong Ju Yan Hai ecosystem becomes better and better,and the gouvernance has achieved good results.3?Ecological Service Function and Assessment of Dongju yan hai WetlandThe evaluation index system of ecosystem service function value is constructed through three aspects,value of economic function,value of environmental function,value of social culture function,and after computation,the total ecological service value of Dong ju yan hai is more than 350 million yuan per year,86.5 thousand yuan per unit of surface,which is much higher than 5.4 thousand yuan of the ecological service value of national unit of surface.Among the three sub-indicators,value of social culture function is larger than the value of environmental function,and the value of economic function is smallest.The proportion of value of social culture function attains 67.82%.4?Analysis of water environment changes and groundwater recharge sourcesThrough the sampling and analysis of specific value of chemical parameters in Dongju Lake,Dongju Lake changed from brackish water(1980)to saltwater(2001)and then to brackish water(2015).The main types of lake water chemistry are always SO4-2–Cl-–Na+–Mg2+.By the construction and calculation of the binary mixture model and the ternary mixture model,the amount of precipitation recharge in the shallow groundwater is 13%,87%is recharged by the river water seepage;the groundwater recharge in the middle groundwater of deep groundwater,which accounts for 51%,and the recharge of shallow groundwater accounts for 30%,the exchange of slowly-renewed water between water layers supplies more than 19%.5?Demand of water for the health of Dongju Yanhai Wetland EcosystemUsing the monthly guarantee rate setting method to calculate the lake area under different guarantee rates,the lake water requirements for the different guarantee rates(50%,75%,95%)is calculated according to this,which are 0.86×10~8m~3?0.77×10~8m~3?0.50×10~8m~3 respectively.At the same time,based on the correlation between entering volume of water and criteria of ecosystem health,the minimum amount of water used for ecological restoration was 0.38×10~8m~3.