Investigation and Estimation of Eutrophication in Large and Medium-sized Reservoirs of the Three Gorges Reservoir in Chongqing

12 large and medium-sized reservoirs in the Three Gorges Reservoir in Chongqing were investigated.The results showed that the total nitrogen(TN) and the total phosphorus(TP) concentrations of all the reservoirs were high.The concentration of the TP,TN,CODMn,Secchi disk depth(SD) and chla varied from 0.017 to 0.258 mg/L,0.718 to 5.941 mg/L,1.30 to 7.03 mg/L,0.42 to 2.00 m and 3.286 to 52.300 mg/m3,respectively.According to the estimation standard commended by Environmental Monitoring Centre of China,all of the reservoirs were from mesotropher to eutrophication.Two reservoirs were hyper eutropher,four middle eutropher,four light eutropher and two in mesotropher level.