Abstract
The NRCS-CN model is one of the commonly used models for the estimation of discharge peak in a watershed in Saudi Arabia using the DEM outputs and daily rainfall data. The current study aims to classify the sub-basins using rainfall volume, rain off volume and estimate the discharge peak using NRCS-CN method. The drainage map of the studied sub-basin areas was extracted from SRTM Dem 30 m outputs. To estimate the surface runoff and its discharge peak, the drainage area was divided into four tributary basins for Wadi Al-Aqiq using the WMS software outputs from SRTM Dem 30 m. The extracted sub-basins were Wadis Rim, Al Yitimah, Al Ishsh and Sha'ib Ruwawah. The results indicate the importance of the integrated use of the digital processing outputs of the DEM in extracting the morphometric variables necessary in calculating the concentration-time, unit peak discharge and the land resources map in determining the runoff curve. In addition, the weighted curve numbers were ranged between 88.4, 89.9, and 92.1 in Wadi Al Ishsh, wadi Rim, and wadi Al Aqiq watersheds, respectively. It was evident that the attained results can be calibrated by the actual recorded discharge and related to several watersheds.