Effect Of Poyang Lake Water Level Change On Water Quality

Poyang Lake is China’s largest freshwater lake, the water environment has always been an issue of much concern.This paper took the Poyang lake’s hydrology and water environmental reaserch as a starting point,to investigate and collect the appropriate data in the basin to carry out related research.First of all, the paper discusses the research background, summarizes the water quality assessment methods at home and abroad. Discussing the water level changes and the impact on water quality and the prediction model apply to the prediction of water quality.Second, analysis the runoff data of five rivers in Poyang Lake basin, from 1956 to 2012, the Poyang Lake basin runoff interannual, years variation characteristics and to determine abundance year,flat year and dry year Then, using single factor evaluation, to evaluate Poyang Lake Basin water quality. Using Decision Tree Algorithm and PSO+KNN Algorithm, to establish a link between the water level of Poyang Lake, area, volume and the main water quality parameters.Then to verify the prediction accuracy of the two algorithms. Finally,using PSO+KNN algorithm to forecast Poyang Lake lake water quality classification from 2010 to 2012.The main research results of this paper are as fllows.(1)Using statistical methods to analysis the runoff data of five rivers in Poyang Lake basin, from 1956 to 2012.Then, to obtain run off interannual variation of Poyang Lake basin. The results show that the interannual variation of Poyang Lake river flow is relatively stable. In the past 57 years, the abundant water year appeared 16 times, the average water years 17 times and the dry years, appeared 24 times. During the year, the flow distribution of Poyang Lake is uneven. The maximum monthly runoff appear in June,and the minimum monthly runoff appear in December or January.(2)According Kangshan,Longkou,Tangyin,Banghu,Piaoshan,Zhuxikou,Duchang, Xingzi, Poyang, Hamashi, Hukou ten monitoring sites of Poyang Lake area, from 2002 to 2009 March, July and November, the three in the monitoring data of water quality, water quality in Poyang Lake area were appraised.The evaluation results are as follows: The Poyang Lake water quality are better than Grade III in July. Water quality does not meet III standards in March of 2006,2007,2009. In other years are better than III standard.Water quality in November of 2005, 2006, 2009, are not met III water quality standards.(3)According to the water quality index of 2002~2008 in Poyang Lake typical sites, Xingzi, Duchang, Tangyin, Kangshan, Hukou and water level the lake area and lake volume data of five typical site. Using Decision Tree Algorithm and PSO+KNN Algorithm, to establish a link between the water level of Poyang Lake, area, volume and the main water quality parameters.Then through the prediction of water quality parameters on the 2009,to verify the prediction accuracy of the two algorithms.(4) Using PSO+KNN algorithm to forecast Poyang Lake lake water quality classification from 2010 to 2012. Overall the predicted results,CODMn、DO、NH3—N water quality indicators can be maintained at more than III water standard. TP water quality indicators can maintain water quality at more than III water standards in July,can not meet III water standards in March and in November.