Abstract

The Shwan Basin –Kirkuk is considered one of the seasonal valleys, with an area of 1371 km2. The research aims to estimate the volume of surface runoff of the basin using the SCS-CN method. This method was implemented within the ArcGIS 10.8 and Landsat 9 OLI satellite data for the basin, which deals with several variables, including land cover, especially vegetation, soil quality and rainfall. The study relied on the highest rainfall intensity during the years 2010-2024, and the soil was classified according to the hydrological soil groups specified by (SCS-CN. The second level of soil moisture, represented by the semi-arid soil condition (AMCII), was chosen according to the tables prepared by (SCS. Based on stream orders, the basin was divided into six sub-basins. The CN values of the basins varied between 62 and 93, main basin dominating the 78 and 85 categories, covering an area of 447.78 and 442.4 km2, respectively. The average depth of surface runoff in the main basin was 23 mm, while in the 6.5, 4, 3, 2, and 1 sub-basins, the values were 16.17, 21.27, 21.91, 23.69, 20.40, and 34.50mm, respectively. The highest surface runoff volume for the main basin and sub-basins occurred in 2019, and the lowest was in 2021 during rainfall events of 150 and 36 mm for both years, respectively.