Pollution load simulation of Dongting Lake basin based on SWAT and GIS

In this study, the Soil and Water Assessment Tool (SWAT) model was applied to simulate pollutant load of the TP and TN of Dongting Lake basin, considering point source and non-point source pollution. Comparison verification was made between water quality monitoring data from Shahekou, Hanshoupotou and Zhangshugang water monitoring stations and simulated results. Three assessment indicators, Re, R2, and E were used to evaluate the availability and suitability of the model. Spatial analysis by GIS revealed that TP and TN load was found to be concentrated in the nearby lake district that merged by sub-basins whose outlets were directly into the lake and the area covered 22 thousand KM2. The pollutant load of TP and TN in the nearby lake district accounts for 39.6% and 45.2%. Xiang River district was the second largest area which account for 13.9% and 12.5% of TP and TN respectively. Yuan River district burdened the least amount of the pollutant load. Contribution rate analysis showed that farmland runoff and aquaculture should be the key factors for pollution. Fertilizer of farmland runoff was the most critical contributor for TN load which account for 32.9% of the total amount, and aquaculture was the largest contributors for TP load account for 47.3%.