Runoff Modeling Using the GIS-Based Curve Number Method

Abstract

To achieve full managment for water resource, accurate records about the quantity and rate of runoff into streams and rivers is crucial since runoff data is required to address watershed development and management challenges. The SCS-CN (Soil Conservation Service–Curve Number) approach calculates hydrological parameters according to the values of soil type and land cover. For any drainage system, these inputs are utilized to create CN grids in a Geographical Information System (GIS) context. The study region is 2,945.33 km² and is situated between the Maysan and Al-Kut administrations in Iraq, north of the Ali Al-Gharbi district. Thus, estimating the CN is the aim of this investigation by utilizing both of soil type and land use/cover with the Digital Elevation Model. The five classes that resulted from the reclassifications were 94.05% agricultural, 2.64% water, 2.54% bare soil, 0.77% urban, and 0.01% forest. The textures of loam soil and sandy clay loam soil are responsible for around 8.44% and 91.56%, respectively, of the watershed area. Since the lowest value indicates minimal runoff, conversely, the estimated CN grid fluctuated between 71 and 100. On the other hand, the area covered by water is indicated by 98 to 100. The predicted CN value ratios were 71-80, 81-90, and 91-100, which were, respectively, 1.44%, 35.08%, and 63.48%. Given that these values closely match the observed runoff. The study region is 2,945.33 km² and is situated between the Maysan and Al-Kut administrations in Iraq, north of the Ali Al-Gharbi district.