Application of SWAT in Hydrological Simulation of Complex Mountainous River Basin (Part I: Model Development)

Suresh Marahatta,Laxmi Prasad Devkota,Deepak Aryal

doi:10.3390/w13111546

Suresh Marahatta, Laxmi Prasad Devkota + Show 1 more

Open Access

https://doi.org/10.3390/w13111546

Copy DOI

Abstract

The soil and water assessment tool (SWAT) hydrological model has been used extensively by the scientific community to simulate varying hydro-climatic conditions and geo-physical environment. This study used SWAT to characterize the rainfall-runoff behaviour of a complex mountainous basin, the Budhigandaki River Basin (BRB), in central Nepal. The specific objectives of this research were to: (i) assess the applicability of SWAT model in data scarce and complex mountainous river basin using well-established performance indicators; and (ii) generate spatially distributed flows and evaluate the water balance at the sub-basin level. The BRB was discretised into 16 sub-basins and 344 hydrological response units (HRUs) and calibration and validation was carried out at Arughat using daily flow data of 20 years and 10 years, respectively. Moreover, this study carried out additional validation at three supplementary points at which the study team collected primary river flow data. Four statistical indicators: Nash–Sutcliffe efficiency (NSE), percent bias (PBIAS), ratio of the root mean square error to the standard deviation of measured data (RSR) and Kling Gupta efficiency (KGE) have been used for the model evaluation. Calibration and validation results rank the model performance as “very good”. This study estimated the mean annual flow at BRB outlet to be 240 m3/s and annual precipitation 1528 mm with distinct seasonal variability. Snowmelt contributes 20% of the total flow at the basin outlet during the pre-monsoon and 8% in the post monsoon period. The 90%, 40% and 10% exceedance flows were calculated to be 39, 126 and 453 m3/s respectively. This study provides additional evidence to the SWAT diaspora of its applicability to simulate the rainfall-runoff characteristics of such a complex mountainous catchment. The findings will be useful for hydrologists and planners in general to utilize the available water rationally in the times to come and particularly, to harness the hydroelectric potential of the basin.

Highlights

Complex interactions between the atmospheric system and the underlying topography determine river discharge
It is a part of rainfall that appears in a stream and represents the total response of a basin
Most of the large rivers in the world originate from the mountains and are perennial in nature as they are constantly fed by snow and glaciers

Summary

Introduction

Complex interactions between the atmospheric system and the underlying topography determine river discharge. Measured flow data are not available in most of the cases in such project sites [5]. It is because of the lack of sufficient flow gauging stations in most river basins. The situation is more severe in mountainous basins [6] because of the inaccessibility of most of these sites for local observations. It is the reason why water budget analyses in such basins are not as easy as in other gauged basins [7,8]. Been considered as the water towers of the world [7,9]

Objectives

Results

Discussion

Conclusion