Study On Evolution Of Snail Islet Habitats Caused By The Water Level Changes

Snail is the only intermediate host of schistosomiasis, inhibited the reproduction and spreadof the snail can achieve the purpose of controlling the prevalence of schistosomiasis. The mostimportant survival factors of snails is Islet habitat. In this thesis, will research Islet habitats ofEast Side scene in the Dongting Lake and observe the water level, soil moisture and vegetationgrowth status of field Islet test site. From the quantitative perspective, study on Islet habitatevolution and distribution changes of snail caused by the change of water level. The mainconclusions are as follows:Through the collection, collation and analysis of water level data, gave a detaileddescription and analysis of history hydrological conditions about Yangtze River and DongtingLake (ChengLingji), and flood water level changes of the Yangtze River and Dongting Lakeunder the Storage Function of the Three Gorges Reservoir in 2010. According to the researchrequirements, conducted a monthly detailed interpretation on the water level changes ofChengLingji in 2010 recession period and using a D model results to restore the water level ofDongting Lake area, analysis water level of the Dongting Lake under the regulating use of theThree Gorges. Concluded that, the regulation of the Three Gorges reservoir made the mainstream of the Yangtze River runoff stable, the highest and lowest water level fluctuationdifferences become smaller; Pre-flood, for vacating flood control capacity of Three GorgesReservoir, increased discharge flow, uplifted water level in Dongting Lake area; Aft-flood, ThreeGorges Reservoir reduced the discharged flow, lowered the water level in Dongting Lake area.Through observed field test site's Islet soil moisture and vegetation growth changes atdifferent times and water levels, and analyzed data from each test observation, Concluded: thegeneral laws of Islet soil moisture and vegetation growth status are the same in differentobservation time periods; The same water level, the elevation decrease, Islet soil volumetricmoisture on average increased gradually; With the lower elevation, the observed vegetation(sedges) number reduced, average height reduced in each 11 square decimetre.According to the Field test results, analyzed the changes of soil moisture and vegetationgrowth staus in different elevation on the Islet at different times Draw the conclusions as follows:In the recession phase Islet, soil moisture were mixed; when the Islet water level close to thebase flow lowest water level, surface and deep soil moisture reached the minimum andmaximum separately; Sedge growth rate is different in different elevation, the higher theelevation, sedges focused on fast-growing time more advanced; Combined with water levelanalysis of the 2010 recession stage, obtained that the sedges was growing the fastest whensedge and water level's elevation difference between 1.3m and 4.5m. Combination of biological characteristics of snail, analyzed the distribution and densitychanges in ribbon of the snail before and after the Three Gorges running; According to changesarea of Islet in Dongting Lake after the Three Gorges running, analyzed distribution and spreadtrends of snail in the region. The results showed that dense ribbon of snail distribution downalong the height after the Three Gorges running; Three Gorges run increased the flooded Isletarea in Dongting Lake, and increased the flooding time, was detrimental to the survival of thesnails, but did not reduce the number of snail on the Islet, snail distribution area is only caused achange or migration.