Water Quality Change And Its Influencing Factors In Bosten Lake

In recent decades,a series of water environmental problems such as salinization,organic pollution and eutrophication have emerged in the Bosten Lake under the comprehensive influence of human activities and climate change.To improve the water quality of Bosten Lake,Bayingolin Management Bureau of Xinjiang Tarim River Basin has implemented the water system connection project for the Bosten Lake since 2018.It diverted the Kaidu River through the Huangshuigou River to Bosten Lake,and opened the ecological gate between the Big Lake and the Small Lake.As a result,these projects have realized the connection between the Kaidu River,the Huangshuigou River,the Big Lake and the Small Lake,with the aim of promoting the water circulation and improving the water quality of Bosten Lake.In view of this,in April,June,August and October of 2019,the fixed-point water quality monitoring was carried out in the Huangshuigou area,the West Bank district,the Big Lake and the Small Lake of the Bosten Lake.In this study,annual change characteristics of the water quality for the Bosten Lake and its driving factors after implement the water system connection project were analyzed,in addition,the measures are put forward to improve the water quality of Bosten Lake by using the methods of inverse distance weighted and correlation analysis.The objective of this study is to provide scientific guidance for further improvement the water environment of Bosten Lake.The main conclusions are as follows:（1）The water circulation of Bosten Lake is effectively promoted by the connection project of the Kaidu River,the Huangshuigou River,the Big Lake and the Small Lake.Duing April-October,the TDS in the northwest and southeast,COD in the Middle East,NH₃-N in the northwest corner,TP in the Northwest and East of the Big Lake decreased significantly,and the TDS in the East,COD in the South and East,NH₃-N in the East of the Small Lake also improved significantly.However,the TP in the Small Lake generally increased.（2）The main exceeding standard indexes of Bosten Lake are TDS,COD and TP,while NH₃-N is not the main factor.The annual changes of TDS,COD,NH₃-N and TP in different regions are both synchronous and different.The TDS of the four districts was the highest in August,the COD of the Big Lake and the Small Lake was the highest in April,the NH₃-N of each district was the lowest in October,and the TP of the Huangshuigou area,the Big Lake and the Small Lake were the highest in October.（3）The water system connection project strengthened the water exchange of Bosten Lake.The rising of water level is helpful to improve the TDS,COD and NH₃-N in the Big Lake and the Small Lake.The pollutants carried by the runoff into the lake are the important sources of the load of TDS,COD,NH₃-N and TP in the Bosten Lake.The water temperature was positively correlated with TDS and NH₃-N in the reed breeding area,the Big Lake and the Small Lake,while showed negatively correlation with COD and TP in the Big Lake.（4）The water quality of constructed wetland inside the dam is generally worse than that of natural river course or water area outside the dam.The main reasons are as follows:1)The concentration of pollutants entering the constructed wetlands is too high;2)Poor water circulation in Constructed Wetland;3)The change of temperature aggravates the change of pollutant concentration in constructed wetland;4)The treatment time of constructed wetland is greatly affected by seasons and human beings.