Estimation of Surface Runoff Volume in Amran Basin- Yemen Using Remote Sensing and Geographic Information Systems Techniques

Abstract

The study aimed to estimate the surface runoff in the Amran basin, one of the seasonal valleys located in western Yemen, with an area of (2110 km²). Additionally, it aimed to build a detailed hydrological database for surface runoff and produce related maps using the (SCS-CN) mathematical model, relying on remote sensing techniques and geographic information systems. By integrating hydrological indicators, including land cover type and land use (LC/LU) and hydrological soil groups (HSG) within the ArcGIS (10.8.1) environment, values of curve numbers (CN) were obtained, indicating that the Amran basin has good hydrological conditions that allow it to generate surface water runoff during periods of heavy rainstorms, attributed to the high values of curve numbers. From the (CN) values, maximum potential values for soil moisture retention after the onset of surface runoff (S) were extracted, along with values of rainfall loss before the onset of surface runoff, depth of surface runoff (Q), and volume of surface water runoff (QV), where (CN) values ranged between (63-94), and the weighted curve number (CNW) averaged (48.93). The values of (S) ranged between (16.21-149.17 mm), and values of (Ia) ranged between (2.24-29.83 mm), while the average (Q) was (149.51 mm). The total (QV) reached (322.70 m³) with an average of (20.17 m³), indicating the potential of the Imran basin to generate surface runoff that can be utilized in water and agricultural development. The concentration time in the basin was (5.91 hours), equivalent to (354.6 minutes), while the discharge amount in the Amran basin was (458.18 m³/s), which is relatively high, attributed to the large area of the basin and the hardness of the rock formations within it, in addition to the high values of (CN) in the basin, thus making the basin susceptible.