Water Quality Assessment and Nutrient Management by SWAT from Sanitation and Agricultural Sources in Warana River Basin, MH, India

Abstract

The Warana river watershed in Western Maharashtra, India has been recognized for exporting some of the highest nitrate-nitrogen loadings in western Maharashtra and is also a major source of sediment and other nutrient loadings. An integrated modeling framework has been constructed with Soil and Water Assessment Tool (SWAT) model and the interactive SWAT CUP. The simulation framework includes a detailed land use and management data such as different crop rotations and an array of nutrient and tillage management schemes, derived from the various source including the state department of Agriculture. This paper presents the calibration and validation of SWAT for the streamflow, sediment losses, and nutrient loadings in the watershed. Streamflow, sediment yield, and nitrate loadings were calibrated for the 1979-1984 period and validated for the 1984-2014 period. Secondary field data on organic nitrogen, organic phosphorus, and mineral phosphorus is used in model to validate for the 2007-2014 period. Model predictions generally performed very well on both an annual and monthly basis during the calibration and validation periods, as indicated by coefficient of determination (R²) and Nash-Sutcliffe simulation efficiency (E) values that exceeded 0.7 in most cases. The first scenario set with application of fertilizer and no sanitation practices and set of land use change scenarios based on taking cropland out of production indicated a significant benefit in reducing sediment yield at the watershed outlet. A second scenario set found that relatively small reductions in nutrient applications resulted in significant reductions in nitrate loadings at the watershed outlet, without affecting crop yields significantly.