Water quality simulation using the WASP model for eutrophication control in a South Indian Reservoir

Abstract The study focused on analysing the eutrophication indicators of the Krishnagiri Reservoir Project (KRP) using the Water Quality Analysis Simulation Program (WASP). The reservoir was divided into six segments to simulate the indicators, and field measurements from 2015 to 2018 were used to calibrate the model while 2019 to 2022 were used to validate it. The results showed that the model predictions were in good agreement with the measured values, indicating the reliability of the model. The study assessed the impact of nutrient loads on dissolved oxygen, nitrate, phosphate, and chlorophyll-a. Four nutrient loading scenarios were simulated, and the most effective scenario (Scenario 4) involved a 75% reduction in nutrient load, which increased the reaeration rate by 1.47% and decreased chlorophyll-a concentrations by 88%. The study concluded that maintaining nitrates below 2.5 mg/L and phosphates below 0.75 mg/L could help restore the KRP reservoir's trophic status from hypereutrophic to mesotrophic. Overall, the study demonstrated the use of the WASP model in developing nutrient loading scenarios to manage reservoir water quality effectively. The findings could help policymakers and managers make informed decisions about reducing nutrient loads and restoring the trophic status of eutrophicated reservoirs.