Analysis of surface Runoff for Some Wadi Basins in Northwest Libya

Abstract

This study has used (SCS, 1986) method with Geographic Information System (GIS) to estimate the surface runoff volumes from the Wadis of Shahobeen, Zghadna, Turghat, Girriem, and Ghunaima which located in northwest Libya. The performance and efficiency of SCS method versus measured data were investigated and other hydrological characteristics such as time of concentration and surface runoff velocity were performed, as well. Many hydrological and morphometric characteristics of the basins such as daily rain storms, the average runoff depth, soil cover, soil maps, soil type, soil permeability and antecedent soil water conditions were taken into consideration in the present study. Based on daily rain storms, the results revealed that the Turghat Wadi basin has the largest amount of the calculated surface runoff volume with 2.94 million cubic meters which was measured during the time of study. It was found the overall measured surface runoff flows surpassed the estimated one by 3%. The highest time of concentration was found in the basin of Turghat Wadi, while the lowest concentration time was for the Zghadna Wadi basin. The highest velocities of surface runoff were found in Qirim and Ghunaima Wadis basin, while the lowest velocities were obtained in Shahobeen Wadi basin. However, the results suggested that it can be relied on SCS model with GIS in estimating the volume of surface runoff in terms of curved values (CN), especially in the absence of sufficient information to measure the flow in some collection basins.

Keywords: GIS, remote sensing, runoff, SCS model.