MAIN PHYSICAL AND CHEMICAL FACTORS IN TIANMUHU LAKE, WITH EVALUATION OF EUTROPHICATION FROM 2001 TO 2002

From June of 2001 to May of 2002, a one year joint study by Nanjing Institute of Geography and Limnology, CAS and Liyang Environmental Protection Bureau was undertaken in Tianmuhu lake. The characteristics of physical and chemical factors,their eutrophic trend and present situation of water quality and eutrophication were analyzed. The results showed that water quality decreased obviously in recent years following the increase of tourists and fishery. Thermocline turned up from March to October, and strengthened from March to May, then weakened from September to October. Water quality did not reach the second class of National surface water standard. Secci disc was in the range 0.5~2.4 m~(-1) (average (1.54 m~(-1))). The annual average values of TN, TP were 0.54 mg/L and 0.003 mg/L, respectively. The average values of abundance and biomass of phytoplankton were 5.026×10~7 cell/L and 15.36 mg/L, respectively. The lake is situated meso to meso-eutrophication and the situation may become worse in the future without effective protection measures.