Determination of Potential Runoff Coefficient using Geographic Information System for a Small Basin in Balakayety Watershade, Kurdistan Region of Iraq

Abstract

Runoff coefficient is an index for losses in rainfall required in most hydrological models and water resources projects. Generally, in the Balakayety water shade in Kurdistan region of Iraq, no runoff data are available as almost basins are ungagged. The Geographic Information System (GIS) techniques and available data for a small basin in Balakayety watershed within the Erbil governorate (Kurdistan Region of Iraq) were used to estimate the coefficient of potential runoff coefficient (PRC). The estimated PRC will be then used to calculate the depth of runoff. The Satellite Imagery (Landsat 7 ETM+) for 2015 was procured to create land cover classes, the classifications accuracy equal to 88.4%, and the Kappa index is 83.7%. The slope map developed from the digital elevation model with 30 m resolution. The area’s hydrologic soil map is digitized from the Iraqi soil map. The inverse distance weighting method was used to interpolate the rainfall of the study area into the Arc GIS. It was found that the most study area covered by moderate to high (PRC) values ranged from 55% to 83%, and runoff depth values vary from 398.1 mm to 610.3 mm. The present study indicates that the integration of all obtained thematic maps into GIS provides a powerful tool for calculating the runoff coefficient for catchments lacks streamflow data which can result in flood/drought predictions that will be not accurate. These findings are helpful in identifying flood areas, selecting proper sites for water harvesting, and enhancing water resources management programs.

Keywords

• geographic information system;
• land cover;
• runoff coefficient;
• slope map;
• soil data