As a result of intensifying human activities around the Changshou Reservoir, water environmental quality has declined over the years. Water quality had been monitored from 1999 to 2002. The result indicated that the concentrations of total nitrogen (TN) and total phosphorus (TP) are high. The concentrations of phosphorus range from {0.037} mg/L to {0.444} mg/L, exceeding the critical value ({0.02} mg/L) for eutrophication. The concentrations of total nitrogen and chlorophyll a range from {0.70} mg/L to {4.18} mg/L and from {1.10} mg/m3 to {61.2} mg/m3, respectively. The eutrophication status of the water body was assessed using the method of integrated nutrition state index, which revealed that all sampling sites were eutrophicated from the year of 2001. About {69.6%} of the annual total nitrogen input and 26% of the annual total phosphorus input originated from the upstreams. The contributions of nitrogen and phosphorus from precipitation to the water body are very small ({0.9%} and {0.3%}, respectively) owing to their low contents ({1.21} mg/L and {0.029} mg/L, respectively). Runoff is the secondarily important input source, which accounts for {19.0%} of the total N input and {47.0%} of the total P input, respectively. Attention should be paid to the aquaculture inputs, whose contributions account for {10.5%} of the total N and {26.6%} of the total phosphorus to the water body, respectively. Nutrient loads are estimated to be 118 gNm{-2}·a{-1} and 8 gPm{-2}·a{-1}. About {69.4%} of nitrogen and {79.7%} of phosphorus input into the reservoir were retained in 2002.
