Investigation of rainfall–runoff modeling for Egypt by using remote sensing and GIS integration

Egypt is characterized as a “water scarce” country, with limited fresh water supplies, and is expected to be under water stress by the year 2030. Therefore, it is important to develop any available means to supply water to maintain human life, such as runoff harvesting approach. The curve number (CN) is a hydrologic parameter used to describe the stormwater runoff potential for drainage areas, and it is a function of land use, soil type, and soil moisture. This study was conducted to estimate the potential runoff coefficient (PRC) using geographic information system (GIS) based on the areaʹs hydrologic soil group (HSG), land use, slope and determine the runoff volume. The soil map of Egypt was extracted from the soil map of the world and then was used in building a soil hydrological group map. Landsat image 5/7 TM/ETM was incorporated with land cover data to generate land use and land cover (LULC) map. Slope map for Egypt was generated from a 30 m DEM. The GIS technique was used to generate PRC map. Annual runoff depth is derived based on the annual rainfall surplus and runoff coefficient per pixel using raster calculator tool in ArcGIS. A variation from as low as 0 to a maximum of 180 mm was observed due to divergence in topography and climate in Egypt where the largest rainfall was observed in the northern part of the country. Generally, the result of this study indicates that in the absence of reliable ground measurements of rainfall, the product can satisfactorily be applied to estimate the spatial rainfall distribution based on values of R and R2 (0.94) obtained.