The evolutionary trend of water environments in the Sihu Lake Drainage Basin

The Sihu Lake Drainage Basin is situated in the center of Jianghan Plain and comprises an area from the north of the middle reaches of Yangtze River to the south of the Han River and the Dongjing River. Due to a long period exploitation of water and soil resources, the water system in Sihu Lake drainage basin has changed dramatically, which is indicated by lake shrinking, water quality and environmental deteriorating. This study reports a monitoring result of water quality of Shihu drainage basin from 1996 to 2008 using the Basic Analytical Methods of Environmental Quality Standards for surface water (GB3838-2002). The purpose of the study is to evaluate and characterize water quality of the lakes and rivers in the region and the water environmental temporal-spatial evolution trends. An analysis method of main pollutants average integrated index is used. The results show that water in the Sihu Lake basin in general are Grade III to Grade IV. The key factors causing the water deterioration are N, P and other organic pollutants. However, diverse evolutionary trends are recognized among the rivers and lakes. It is also illustrated that these environmental evolution trends are closely related to human economic activities, including agricultural non-point source pollution, industrial point source pollution and domestic sewage pollution.