Estimation of Annual Runoff of Galal Badra Transboundary Watershed Using Arc Swat Model, Wasit, Eastern of Iraq

Abstract

Optimal investment of natural water resources in an area is an effective way to provide significant amounts of water that can contribute to reduce the negative impacts of climate extremism. Proper assessment of the components of any hydrological system is a priority in watersheds studying. SWAT (Soil and Water Assessment Tool) model was used within ArcGIS, to assess the hydrological situation in general, and surface runoff in particular for Galal Badra Watershed GBW (Wasit Governorate, eastern Iraq). GBW has an area of 2,655 square kilometers (89% of which is in Iran and the rest 11% within Iraq). The data set for SWAT model running were digital elevation model, slope map, soil map, LULC map, and climatic data (precipitation, relative humidity, wind speed, solar radiation, minimum/ maximum air temperature). SWAT simulation concluded that the annual average surface runoff in GBW was 244x106 cubic meters (with an average discharge of 7.8 M3 / s), which accounts for about 25.7% of the total precipitation. This ratio can be used in preliminary forecasting of surface runoff resulting from different amounts of precipitation. The model was not calibrated due to insufficient data available to complete the calibration process. However, the results provided by the SWAT model regarding the water balance elements in the watershed, make the SWAT model an effective tool for hydrological assessments, especially in cases where the necessary data are scarce for various reasons. Also, SWAT results can be considered as a preliminary assessment, which gives an overview of the hydrological situation of the area, contributes to building an initial perception of the water system, determining the most important elements in it, and anticipating the factors most influencing it. This enables policymakers, decision-makers, and stakeholders to adopt future plans at the level of research and implementation that will develop the reality of water investment in the region under conditions of climate extremism.