Swat based runoff and sediment yield modelling for Nagwan Watershed
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Date
2018-08
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Physically based Soil and Water Assessment Tool (SWAT) model was setup and assessed for the runoff and sediment yield from Nagwan watershed (98.42 km2) situated in Hazaribagh district of Jharkhand. The runoff parameters namely effective hydraulic conductivity in the main channel, SCS curve number, base flow alpha factor for bank storage, manning’s “n” value for the main channel and saturated hydraulic conductivity of soil layers were found to be the most sensitive. The sediment yield parameters namely, sediment that can be re-entrainment during channel sediment routing and average slope steepness, exponential parameter for calculating sediment re-entrainment in the channel sediment routing and average slope length were found to be the most sensitive. The statistical indicators of R2, NSE, PBIAS and RSR for monthly runoff during calibration period were found to be 0.74, 0.84, 9.80 and 0.51 respectively. Similarly for validation period value R2, NSE, PBIAS and RSR were found to be 0.77, 0.66, 10.50 and 0.58 respectively. For monthly sediment yield the R2, NSE, PBIAS and RSR during calibration were 0.83, 0.82, 5.90 and 0.42 respectively. The values of R2, NSE, PBIAS and RSR during validation period were 0.71, 0.67, 17.10 and 0.58 respectively indicating the model performance was good for both runoff and sediment yield simulation which are adequate for SWAT model application for management planning. Such successful evaluation of SWAT model as illustrated in this study can widen model applicability into other ungauged basins. The critical sub-watersheds were identified on the basis of sediment yield annually from the SWAT simulated values during period of 2007 to 2013. Out of fifteen sub-watersheds four watersheds were found to be under very high soil loss, six under high soil loss, one under moderate and four under slight soil loss group.
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