Eutrophication modeling in Shihmen Reservoir, Taiwan.

Based on the measured data, including total phosphorus, chlorophyll a, and Secchi disk depth, the Shihmen Reservoir in the state of mesotrophic to eutrophic. A two-dimensional, laterally averaged, finite-difference hydrodynamic, and water quality model was applied to simulate water quality conditions in the reservoir to determine appropriate strategies for the management of water quality. Data collected in the field for a two-year period were utilized to calibrate and verify the model. The model calibration and verification were achieved with water surface elevation, temperature, and water quality constituents such as nutrients, dissolved oxygen, and chlorophyll a. Then the model was used to simulate chlorophyll a concentrations under several scenarios corresponding to various waste load reduction ratios. A 90% reduction of nutrient loadings will upgrade the existing eutrophic/mesotrophic conditions to oligotrophic condition in both 2001 and 2002, exception January in 2001. The modeling effort had yielded valuable information that can be used by decision maker for the evaluation of different management strategies of reduction of nutrients coming from the catchment area.