Impacts of seasonal thermal stratification on the water environment of Wanfeng Lake

The water temperature and hydrochemical parameters during September 2009 and January 2010 of Wanfeng Lake in Guizhou Province were surveyed.A clear thermal stratification was found at the vertical profile of water column in autumn and winter.In autumn,a double thermocline appeared,which effectively limited the convective mixing of upper,intermediate and bottom of the layer water,caused water and water chemistry layed significantly.In winter,with the decreasing temperature of upper layer water,because the subsidence of the upper water due to the density changing,the water stratified structure changed,and convection exchange appeared between the upper and the bottom water,so the reducing matter released by anaerobic digestion was brought into the upper layer water.Seasonal thermal stratification played an important role in water quality and environmental change of Wanfeng Lake.Correlation analysis shows that,in Wanfeng Lake,the water temperature was significantly correlated with hydrochemical parameters(DO,pH,and total phosphorus) in September of 2009 and January of 2010,thus water chemistry layered with the temperature stratification synchronization.