Estimate nutrients loading from different land use/land cover using distributed hydrological model SWAT

The loading rates of nutrients (TN, TP) to streams from various land uses in the basin could show significant difference. In this study, Honghu Lake Basin, located at the mid-reach of Changjiang River, was chosen as the study area, and the watershed distributed hydrological model SWAT (Soil Water Assessment Tool) was applied. The model provides estimates of total nitrogen and total phosphorus loading rates to streams for. each land use. Although other factors impact model predictions (e.g. land slope and soil type), it can be useful to determine the relative importance of land use in the basin with respect to nutrients loading to surface waters. Boundary conditions in the simulations was prescribed as follows: 1: 250000 digital elevation models, 1: 1000000 digital soil map with spatial and non-spatial information, 1:100000 land use map of 1980s, 1995 and 2000, and 1983 similar to 2002 daily temperature/precipitation/solar radiation/wind speed/relative humidity data. Simulation results showed that the impact of land-use on nutrient production and transport varies from different land-use types, such as cropland, forest, resident area, et al., among which cropland has the highest nutrient produce per area (Riceland has a TN production of 1720kg/km(2)/a, TP production. of 332kg/km(2)/a, and dry land has TNI189kg/km(2)/a; TP247kg/km(2)/a respectively) forest is in the second high production, and resident area is the lowest.