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

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.

Hydrological Modelling for Reservoir Operation: Application of SWAT Model for Kalu Ganga Catchment, Sri Lanka

“…The model is conceptual and computationally efficient, uses readily available inputs and enables users to study long-term impacts [24]. The SWAT is internationally recognized as a solid interdisciplinary watershed-modelling tool with diverse applications [23,25,26,27]. It can be used to simulate a single watershed or a system of multiple hydrologically connected watersheds.…”

“…In the SWAT model, there is a large number of input parameters related to the land use (e.g., SCN curve no) and soil types (e.g., available water capacity of the soil, hydrologic group of soil). A set of model parameters based on the experience from previous studies [2,27,28,32] were carefully selected for the calibration of the model and they are given in Table 6…”

Runoff simulation and projection in the source area of the Yellow River using the SWAT model and SSPs scenarios

“…Since the hydrological model is able to provide a significant amount of information from limited existing data and identifies the relationship between model parameters and physically observable land surface characteristics, it is the main method currently used for runoff simulation. The three types of hydrological models used in practical applications are the lumped, semi-distributed, and fully-distributed models, which are based on spatial discretization (Marahatta et al, 2021a). For example, Génie Rural à four paramètres Journalier (GR4J), Hydrologiska Byråns Vattenbalansavdelning (HBV) and a simplified version of the HYDROLOG (SIMHYD) are lumped models, while topographic hydrologic model (TOPMODEL), Variable Infiltration Capacity (VIC) and the SWAT are semidistributed models.…”

A framework to estimate continuous streamflow at the ungauged site with limited catchment’s hydrological data: Case study Isahaya Catchment

“…The size and structure of watersheds as well as their topographic and geographic structures vary significantly due to geological, morphological, vegetation, soil, and climatic differences (Loukas & Vasiliades, 2014, Marahatta et al, 2021. In response to human development, fast climate dynamics, and slow geologic processes, there has been a reciprocal evolution within catchments resulting in changes in the soils, vegetation, and topography, mediated by material and energy fluxes.…”

“…The SWAT (Soil and Water Assessment Tool) is an open-source distributed model (Arnold et al, 1998 that has a large and growing application in the hydrological characterizing of catchments (Asurza & Lavado, 2020). Regarding previous studies, the tool has shown strength in discharge estimation in mountainous catchments (Koycegiz & Buyukyildiz, 2019, Luo et al, 2011, Marahatta et al, 2021, Yacoub & Foguet, 2013. The model has successfully been used to estimate flow rates on a wide scale and in various hydrological regions.…”