Evaluation of SWAT Model for Simulating the Water Balance Components for the Dudh Koshi River Basin in Nepal

Abstract

Evaluation and quantification of components of the hydrologic cycle is an essential step towards making any development and/or management plan for any river basin. The present work perceives and evaluates the major elements of the water cycle in the Dudh Koshi River Basin (4017.69 km2) in the Himalayan region of Nepal with the usage of the soil and water assessment tool (SWAT). The monthly calibration (1982--2000) and validation (2001--2006) of the SWAT model had been performed using the local discharge records at Rabua Bazar, Nepal, using the SWAT-CUP programme. The basin's average annual precipitation is 2197.19 mm for the study period. 340.77 mm (15.5{\%}) of yearly precipitation returns as average annual evapotranspiration from the basin. The average annual water yield at the basin outlet is 1578.40 mm, with a total of 6.34 BCM. From the monthly distribution of water balance components, it is found that 79.40{\%} of precipitation, 88.90{\%} of surface runoff, and 76.80{\%} of water yield occur during four months of monsoon.