Research On Ecological Risk Of Chagan Lake Caused By The Return Water Of Songyuan Irrigation

Northeast China is a typical wetland ecosystem distribution area. The abundant wetland resource there affords local important guarantee for the commodity grain production. Chagan Lake is a compound ecosystem which is made up of many kinds of wetland ecosystem such as lake, swamp and swamp meadow, and it provides a lot of insignificant ecosystem services such as climate regulation, flood control for the increase of agricultural production and the maintenance of regional ecological balance.Songyuan irrigation is not only the important project of the construction of increasing grain production in Jilin province but also the complement of Hadashan hydro junction project. So the implementation of Songyuan irrigation is important to the saline-alkali soil transforming, the increase of grain production, and the economic development of the region. However, as the great ecological benefits brought from the implementation of Songyuan irrigation, some ecological risks are also loaded into the wetland ecosystem. In order to improve the future sustainable management of the Chagan Lake, this dissertation evaluate the ecological risk of the return water of Songyuan irrigation on the Chagan Lake based on the assessment of the water environmental quality assessment, and propose some precautionary measures and policy advices.This dissertation is mainly divided into the following sections:The first part demonstrates the background of this research, the research progress and the methods of ecological risk assessment. It helps the establishment of the research purpose and significance.The second part of this dissertation describes the general situation of Songyuan irrigation including the basic profile of irrigation scale, irrigation area, irrigation water resource, and the irrigation partitioning.The third part first describes the general situation of the Chagan Lake, then the water quality of the Chagan Lake is analyzed based on the principal component analysis and fuzzy comprehensive evaluation, which lays the foundation for the next step of ecological risk assessment.The fourth part of this research mainly studies the regional risk difference and the total ecological risk of the Chagan Lake caused by the return water of the Songyuan irrigation. In this part, the salinity, the nitrogen, the phosphorus, and the pesticide are selected as the major risk sources in the return water, and the comprehensive evaluation system composed of fertilizer, salt, and nutrition indexes is used to evaluate the ecological risk. The results show that, Daan irrigation and Qianguo irrigation belong to the high level risk, Youzi irrigation and Hongxing irrigation are part of the moderate level risk, and others fall within the lighter level risk. So the ecological risk may be caused if the return water of Songyuan irrigation is discharged in Chagan Lake.The last part of the article mainly puts forward some prevention measures and management suggestions which aimed at preventing the ecological risks of the Chagan Lake caused by the return water of Songyuan irrigation.