Abstract:
The major goal of the present study was to identify the critical erosion areas of an agricultural
Kora watershed and recommend the best management practices using a physical process-based
watershed scale model, soil water assessment tool (SWAT). The semi-automated Sequential
Uncertainty Fitting (SUFI2) calibration process built in SWAT calibration and uncertainty
program (SWAT-CUP) was used to calibrate the model parameters using time series of flow
and sediment load data of 1997 to 2006 and validated with the observed data from years 2007
to 2011. The performance of the model was evaluated using graphical methods to assess the
capability of the model in simulating the runoff and sediment yield for the study area. The
coefficient of determination (R2
) and Nash Sutcliff efficiency values for the daily flow
calibration using SUFI2 are 0.89 and 0.89 respectively for validation and it was 0.89 and 0.88.
For daily sediment yield by using SUFI2 calibration technique the model evaluation
coefficients R and NSE for calibration was computed as 0.87 and 0.88 respectively, for
validation it was 0.86 and 0.86 respectively. The sensitivity analysis runoff and sediment
producing parameters was also carried out and discussed. This paper presents sediment yield
simulations in the Koga watershed under different Best Management Practice (BMP)
scenarios. Scenarios applied in this paper are (i) Base scenario (Jones et al.) Applying terraces
(ii) (iii) contouring (iv) introduce strip cropping. The scenario results showed that applying
terraces, contouring and introducing Strip cropping reduced sediment yields both at the sub
watershed and the watershed outlets. Considering the critical sub watershed for the existing
conditions scenario (Base scenario), the model result indicates that simulated annual average
sediment yield was 33.45 t/ha/yr. Depend on this from base scenario terraces are saving 18.45
tons/ha/year of soil loss. Contouring was found to reduce soil erosion by 10.54 tons/ha/year.
Strip cropping for agricultural fields in the watershed reduces erosion also by 8.75 tons/ha/year.
These results indicate that applying BMPs could be effective in reducing sediment transport
for sustainable water resources management in the watershed
