Soil and Water Assessment Tool Applications for Hydro-environmental Assessments in Sri Lanka: A Review

Abstract

Soil and Water Assessment Tool (SWAT) is a distributed hydrologic model that considers the spatial variability of physical properties of a catchment. SWAT is a public domain model which has been applied to address a wide range of hydrological and environmental issues worldwide. Compared to the global applications of SWAT, only a limited number of applications are touched on in the Sri Lankan context, and more potential applications in the hydro-environmental field have yet to be explored. Being a distributed model, SWAT requires a lot of model input data but has the best structure representing a catchment with hydrological response units, resulting in accurate model output. Therefore, SWAT applications for Sri Lankan catchments are encouraged. Thus, based on the literature, this study delves into the existing applications of SWAT in the Sri Lankan context and explores its potential applications for soil, water and land management in Sri Lanka compared to the global context. According to the SWAT applications in the Sri Lankan context, most of the studies focused on runoff simulations. Moreover, several studies have been conducted to understand the effects of sediment loads and estimate parameters for ungauged catchments. Some studies focused on water availability assessments in catchments under climate change impacts. However, in comparison to the global context, some import-ant hydro-environmental impact assessments were not conducted to a satisfactory level in Sri Lanka, such as soil erosion estimates, land-use change impact analysis, best management practices identification for improved irrigation efficiency, water quality assessments including point and non-point source pollutant estimates, nutrient cycling and transport simulations, and predicting the impacts of agricultural practices. As per the aforementioned research gap, a need exists to expand SWAT fields of applications that received limited attention in Sri Lanka. As such, this review is a dedicated call for hydro-environmental researchers urging further exploration.