Sediment yield prediction and prioritization of sub-watersheds in the Upper Subarnarekha basin (India) using SWAT

Abstract

The present study deals with the estimation of soil loss from the Upper Subarnarekha catchment in Odisha (India) using Soil and Water Assessment Tool (SWAT). Sequential uncertainty fitting (SUFI-2) algorithm of the SWAT calibration uncertainty programs (SWAT-CUP) was used for model simulation. The model was calibrated with the observed data for the period from 1996 to 2008 with first 3 years (1996–1998) as warm-up period. Further, validation of the model was done using 5-year data from 2009 to 2013. Reliable evaluation of the model performance during calibration has been substantiated by the coefficient of determination (R2), Nash–Sutcliffe efficiency (NSE), and percentage bias (PBIAS) as 0.81, 0.81, and −0.15, respectively, and the respective values for the validated model were found to be 0.79, 0.78, and −0.19. The values of P-factor and R-factor were found to be 0.80 and 0.75 and 0.66 and 0.74, respectively, for model calibration and validation. Average annual soil loss from the catchment was 4.84 Mg ha−1. The watershed indexed as SW18 resulted in highest soil loss in the range of 10–15 Mg ha−1year−1. Further, prioritization was done at the level of sub-watersheds using the data of simulated sediment yield, soil texture, land use, and slope for identifying vulnerable sub-watersheds that need immediate attention. The study inferred that sub-watersheds having index numbers SW17, SW18, and SW19 are highly vulnerable, and hence top priority should be given to these sub-watersheds for reduction in soil erosion through the implementation of suitable soil and water conservation measures.