A brief report on online training on Soil & water Assessment Tool (SWAT), Feb28-04March 2022

Abstract

Water is a vital natural resource. Hydrological modelling is an essential aspect of any development project for planning, designing, executing, and managing water resources efficiently. A hydrologic model simplifies a real-world system (e.g., surface water, soil water, wetland, groundwater, estuary) that aids in understanding, predicting, and managing water resources. Both the flow and quality of water are commonly studied using hydrologic models. SWAT is widely used in assessing soil erosion prevention and control, non-point source pollution control and regional management in watersheds. This training course was designed to impart and transfer the working knowledge of a popular semi-distributed hydrological model called the Soil & Water Assessment Tool (SWAT). This model is a small watershed to river basin-scale model used to simulate surface and ground water quality and quantity and predict the environmental impact of land use, land management practices, and climate change. SWAT, a river basin or watershed scale model, is a physically-based, spatially distributed, continuous model that operates on a daily time step. It is a product of four decades of modelling efforts by USDA-ARS, USDA-NRCS and Texas A&M University. It was developed to predict the impact of land management practices on water, sediment and agricultural chemical yields in large complex watersheds with varying soils, land use and management conditions over long periods. It can incorporate the effects of tanks and the reservoirs/check dams off-stream as well as on-stream. The significant advantage of SWAT is that it does not require much calibration. Therefore, it can be used on ungauged watersheds and predict relative impacts of alternative scenarios such as changes in management practices, climate and vegetation on water quality and quantity. Model output includes all water balance components at the level of each watershed and is available at daily, monthly or annual time steps. SWAT model has been extensively used to address water resources and nonpoint-source pollution problems for various scales and environmental conditions across the globe. SWAT allows several different physical processes to be simulated in a watershed. A watershed may be partitioned into many sub-watersheds or sub-basins for modelling purposes. Thus, a user can reference different areas of the watershed to one another spatially. The input information for each sub-basin is grouped or organized into the following categories: climate; hydrologic response units or HRUs; ponds/reservoirs/ wetlands; groundwater and main channel, or reach, draining the sub-basins. HRUs have lumped land areas within the sub-basin that are comprised of unique land cover, soil and management combinations. SWAT typically uses the ArcSWAT interface to create inputs that work in the licensed ArcGIS environment. The Quantum GIS (QGIS) is a free and open-source GIS that performs most of the functions of commercial GIS. Given its robustness and wide use in academic and professional environments, the present training course was conducted using QSWAT, a QGIS interface for the SWAT model.