Study On Ecological Water Level And Water Regime Of The Dongting Lake Under Water Volume Changes

Dongting lake is China’s second largest fres hwater lake, is also the world’simportant wetlands. Special geographical locatio n and regularity hydrologica l processmakes the Dongting lake has formed the divers ity, stability of wetla nd resources.Provides a suitab le growth e nviro nment for various k inds of vegetation and creatures.Is known as "The main hopeful p lace to o save the world e ndangered r are b irds".Itplays a irreplaceable role for economic and socia l deve lopment in Hunan Provinceand ease the middle reach of Yangtze river flood s.In the north, Dongting lake connected with the Yangtze River thro ugh the theSongzi, Ta iping, Ouchi three outlets. Meanwhile it absorbs the water from four rivers:the Xia ng River, the Zi River, the Yuan River, the Li River in the south. In recentdecades, A large number of water conservancy project has been built, under the watervolume cha nges, especia lly after the impound ment operatio n of the Three GorgesProject has caused some prob lems suc h as the lake area reducing, the water leve ldrops, fish, birds and other bio logica l resources has been damaged. Water, as the mostimportant contro l factor of the lake ecolo gical e nviro nment, in severe cases, itsdama ge can cause the degradation o f Lake ecosyste ms and eve n the loss of lakefunction.This artic le proposed a calculatio n method of ecolo gical water leve l suitab le forDongting lake. Dongting lake wetla nd has been suffering fro m progress ivedegradatio n late ly, Wetland ecosyste m is considered to be adapted to hydrologica lsequence before alteration caused by climate cha nges and human re lated activities.Average mo nthly water-le ve l of Chenglingji stations in Do ngting Lake regio n wereanalyzed to obtain ecolo gical water-leve l in this paper. The point of the highest Tstatistic va lue calc ulated by moving T-test method is April1980and was consideredto be the alteratio n point. The sequence was then divided into two parts. Thesubsequence before alteration po int was used to find the most fitted probabilitydistribution function. The ecologica l water-leve l was cons idered to be the average monthly water-leve l of the highest probability of the probability distrib ution funct ion.This method calc ulated annua l avera ge water leve l o f Dongting Lake Ecologica l is24.29m.Based on previous research on Dongting Lake, the water le ve l processes ofChenglingji Statio n in the time after flood season were simulated by us ing BP neura lnetworks, and proposed the TGR d ispatching Optimization based on ecologica lwater-le ve l. It results that in the time of water storage after flood season, the waterleve l o f Do ngting lake was able to ma intain the ecologica l water leve l when thedischarge reach11000m~3/s.Xia ngjia ng river, as the biggest trib utary of the Dongting Lake. This artic ledeve lop a mathe matica l model for analyzing and predicting the flow and water qualityin Xia ngjia ng river (Chang-Zhu-Tan section) with meandering channe l, bottomlandins ide the river. Extracted the actual s hape of Xia ngjiang river in remote sens ingima ge, based on the Navier-Stocks equation and pollutant transport equations, thecoup led two-dime nsio na l flow and pollutant transport model is deve loped. The resultshows that: under the water vo lume change, the flow rate of Xiangjia ng river slowddown, it caused the non-conservative pollutant (CODcr and Ammonia) concentrationincrease. The concentration of CODcr increased0.9~5.2mg/l, Ammo nia increased0.07~0.35mg/l after the operation of Changsha water conservancy project.