Study On The Groundwater And Ecological Landscape Influenced By Water Diversion Project In Da’an County

Da’an County, located in the western of Jilin Province, an inland dry area, is in anoverall and server shortage of water. Ecological environment of this area is vulnerableand the main problems existed are salinization, desertification, rangeland degradationand marsh wetland atrophy. In order to solve the problem of water shortage andguarantee food security and water supply security Jilin Government formulated a planfor land arrangement and management in2007. The details were using water from theNen River to establish Da’an Irrigation District, reclaiming the uncultivated land,transforming the middle-and-low-yielding fields and changing dry farmland to paddyland to increase grain output and farmers’ income. Because of located in low plain ofSongnen Basin, the depth of groundwater table is shallow and groundwater runoff isstagnant in Da’an County. Water diversion project will increase groundwater rechargeand raise the regional groundwater table. On one hand it may result in soil salinizationand then damage the ecological environment; On the other hand, the rise ofgroundwater level can provide adequate moisture for grass growth and is benefit ofrestoration of degraded grassland and mitigation of land desertification. To solve theabove problem, identify a suitable groundwater table to maintain the ecologicalenvironment of the study area to a good direction and analysis the influence of thewater level changes after the irrigation district running on the surface ecologicalenvironment is necessary.The paper briefly introduced the conditions of nature, economy, geology andhydrogeology of Da’an County. Based on remote sensing technology, the distributionof ecological landscape of the study area in different periods was interpreted. Therelationship between groundwater depth and distribution of ecological landscape wasanalyzed by using spatial analysis function of GIS. A numerical simulation model ofgroundwater flow system was built based on analyzing and conceptualizing the localgeological and hydrogeololgical conditions and solved by Visual Modflow. Theresults show that the model-simulated water heads match the measured historicalwater heads well and the model can be used to predict the groundwater flow fieldevolution. Evolution of groundwater flow field after irrigation district running was predicted under different precipitation condition. The impact of irrigation on thedistribution of ecological landscape was analyzed according to appropriate depth ofdifferent ecological landscape.The results showed that:(1) There is a certain degree correspondence betweengroundwater table and distribution of the ecological landscape. The area of burialdepth less0.5meters is usually occupied by water body and0.5-3meters is mainlyoccupied by saline-alkali soil. High coverage grassland is concentrated in the depth of3to5meters region.(2) The regional groundwater level will rise after irrigationdistrict running10years in different precipitation conditions. Groundwater level risesinside the irrigation district is slightly larger than the outside.(3) Based on thepredicted water level the impact of irrigation on ecological landscape is analyzed andthe area where may occur salinization is predicted (4) Water diversion project is ofgreat significance for wetlands protection and vegetation recovery.