Research of the Characteristic of the Seasonal Thermal Stratification in Shanzi Reservoir,Fujian Province

Surveied the water temperature and hydro chemical parameters during the twelve monthes in 2005 of Shanzi reservoir of Fujian province.The result showed that an clear thermal stratification had been formed at the vertical profile of water column from March to November in shanzi reservoir.It could cause very strong stratification of the dissolved oxygen especially in summer and there was an anoxic hypolimnion companying with processes of organic maters degeneration between the surface sediment and the overlying water.The results also confirmed that unstable of the thermal stratification caused by surface cooling of water when the air temperature decreased abruptly from twelve to the next January and February would lead to a vertical convection between the upper layer water and the deep layer water.The reductants formed in the anoxic hypolimnion would be brought to the epilimnion through the vertical eddy diffusion.This study showed that the seasonal thermal stratification could play a key role in change of water quality in shanzi reservoir.