Hydrological Regime And Regulations Of Ecological Water Demand In Chagan Lake Wetland

Chagan Lake Wetlands National Nature Reserve is one of the mostimportant lake-wetlands in Northeast China. Functions of the wetlandsinclude regional climate modification, flood protection, water and wildlifehabitats, public education and scientific research. However, global climatehas changed and the hydrological regime of Chagan Lake has changed,accompanying with the increased of mercury and evaporation. Rainfall inthe region is much less than evaporation and, as a result, water shortage isoccurring in Chagan Lake. Moreover, anthropogenic activities, such asconstruction of reservoirs, water diversion projects, and the increasingirrigation and water saving reconstruction projects, possess a serious threatto the Chagan Lake water health and security. This thesis provides aneffective ecological water demand projection for Chagan Lake based on acomprehensive study of hydrological regime and calculation of ecologicalwater demand.1Analysis of the hydrological regime in Chagan Lake. In this paper, thecomprehensive study is carried out to analyze the long-term trends of lakewater level, lake water storage change, evaporation and precipitation.Meanwhile after correcting remote sensing image, we analyze it usingArc-map to obtain the long-term trend of the Chagan Lake water surfacearea. Based on the relationship between water level and storage capacity, therelation between maximum water storage and surface area is proposed. This study establishes a water budget and the results indicate a strong interactionbetween surface and groundwater in the Chagan Lake Wetlands functioningas a discharge zone receiving annually0.66×108m3from the shallowgroundwater.2Ecological water demand in Chagan Lake. Based on lake morphologyanalytical approach, this study establishes the relationship between waterlevel and change rate of water surface area of Chagan Lake. Calculatingresult shows that the minimum ecological water level is129.5m. Thecomprehensive analysis is carried out, we find the suitable water level inChagan Lake to be130.00m. Considering the relationship among waterlevel, water area and the quantity of ecological water demand, we calculatethe minimum and suitable ecological water demands. Results show theminimum ecological water demand is3.90×108m3, and the suitableecological water demand is4.33×108m3.3Ecological water regulation schemes in different scenarios.(1) Pledge probability of precipitation scenarios.Based on precipitation data, four scenarios are designed. The scenariosare P (precipitation frequency)=10%, P=50%, P=75%and P=90%respectively. After compared with the ecological water demand and naturalwater, conclusions are manifested that: Meeting the minimum ecologicalwater demand, the ecological water dispatching are0.63×108m3,1.24×108m3,1.41×108m3,1.51×108m3respectively；Meeting the suitable ecologicalwater demand, the ecological water dispatching are1.06×108m3,1.67×108m3,1.84×108m3, and1.94×108m3, respectively。 (2) Irrigation water scenarios.Chagan Lake is an important grain-production region with abundantwetlands in Jilin Province. More and more irrigations were undergonearound Chagan Lake. In order to identify potential water storage, fourschemes were designed referring to the agricultural irrigation constructionsand plans. After calculating, results showed that there were1.3×108m3volume which could be used to store additional water, and the water quantityof Qianguo and Da’an irrigation could be transferred to Chagan Lake, butQian’an irrigation could not. After Water Conservation&TransformationEngineering, in order to meet suitable ecological water-table demand, aquantity of water is needed to be diverted.