Abstract:

Excessive input of nitrogen and phosphorus is always the main problem in the Taihu Lake basin, and it is important to cut the nitrogen and phosphorus loading from the catchment and control the water quality in the inflow rivers efficiently. The TN and TP standards in national surface water environmental quality standards of China (GB3838-2002) have discrepancy between rivers and lakes. That is, the lack of the TN standard for rivers and the inconformity between the TP standard for rivers and lakes. Thus, the pollutant control objective in lake is difficult to meet by restricting the nutrient input from rivers under nowadays’ guideline. This paper took the northwest of the Taihu Lake and its inflow rivers as case study and used the BATHTUB model to simulate the correspondence between the concentrations of TN and TP in the inflow rivers and lakes. Then a plan to revise the nitrogen and phosphorus control was proposed for the inflow rivers in the northwest of the Taihu Lake. The modeling results showed that: 1. If the inflow rivers implement the TP standard for rivers in the GB3838-2002, the TP concentration in lake would exceed its own standard and couldn’t achieve the environmental goals. 2. Provided the inflow rivers implementing the TN and TP standards for lakes in the GB3838-2002, the associated TN and TP concentrations in the lake could fulfill their environmental goals in GB3838-2002. However, this plan is lack of practical significance due to the poor water quality background in the Taihu Lake. 3. If the TN and TP concentrations for inflow rivers are inferred according to each environmental goal for lakes in the GB3838-2002, the result is more practical to implement and could guarantee the water quality in the lake. Our results may give a reference to the revise of nitrogen and phosphorus standards for inflow rivers and then the water quality in the northwest of the TaihuLake can be improved.

Key words：BATHTUB; the Taihu Lake; inflow rivers; TN;TP; water quality standard