Estimating runoff using the Natural Resources Conservation Service (NRCS)-Curve Number (CN) is one of the most common methods used worldwide. The WMS Software facilitates accurate estimating of surface runoff from the Erbil basin. The present paper evaluates the applicability of the NRCS-CN method using the Watershed Modeling System (WMS) application in the Erbil basin, KRG, Iraq. The software required a digital elevation model (DEM), hydrologic soil groups (HSG), and Land use Land cover (LULC) shapefile as input data. Then, the WMS processed and calculated the weighted CN for each sub-catchment area within the study area, giving the total weighted CN for the basin. The results estimated that the high Runoff amount was obtained in (2018-2019) because the annual depth of the daily rainfall data was recorded as (1008, 769.7, and 1002.60) mm, and depth of runoff for (2018-2019) were calculated as (181.79, 127.48, and 266.73) mm, respectively, for the stations in Erbil, Khabat, and Qushtepa. As a result, the average volumes of the sub-basins of Central, North, and South, part of Erbil, were calculated as (101,083,979.17; 27,793,570.64; and 30,741,656.15) m3, respectively. Also, the average weighted curve number for 12 sub-catchment results estimated by WMS was (76.1), involving 12 sub-catchment areas. Whereas the results of CNI and CIII were (57.2 to 88) for dry and wet conditions. The kappa method was used to determine the overall accuracy of the LULC map in (2022). The result showed that the overall accuracy was 91.94%, and the Kappa coefficient (Ka) was 0.89, which is acceptable and perfect and verified the results’ accuracy.
Mustafa et al. (Wed,) studied this question.