Abstract
Scarcity of measured hydrologic data is the main cause for difficulty in demonstrating the assessment of groundwater recharge. The aim of this study is to provide a new scope to assess the runoff and groundwater recharge in ungauged basins based on paleo-flood and morphometric features in arid environment in spite of limited hydrological data. This study is based on rainfall-runoff modeling through the integration between paleo-flood mark measurement, basin physiographic features, and geographic information system (GIS) techniques. Four models of ArcHydro, Grinne (channel) model, Watershed Modeling System (WMS), and HEC-HMS were integrated together and used to assess flood risk and the relationship between rainfall and runoff in the study basin. Al Dawasir basin was selected to demonstrate this study, because it is the biggest basin in the Kingdom of Saudi Arabia with an area of 257,689km(2) and extends for about 700km from Makkah al-Mukarramah region in the west side of Saudi Arabia to Riyadh region and the Rub` Al Khali in the middle of Saudi Arabia. Al Dawasir basin which has stream order reaches to 8th order, composed of 2 sub-basins of 7th order, 12 sub-basins of 6th order, and 44 basins of 5th order. This study deals with the hydrological study of large sub-basins of highest order (7th and 6th) such as Al Fushsh, Turbah, Al Khurmah, Ranyah, Bishah, Shiab Yafikh, Tathlith, Al Hinu, Al Maqran, Himam, and Uyaynah sub-basins. Wadi Al Dawasir Basin is usually subjected to sporadic storm events, which vary spatially and temporally in intensity. Based on the paleo-flood measurement of Wadi Ranyah sub-basin, calibrated scenarios have been done and the resulted hydrograph is matching with rainfall event of 10-year return period with and without routing scenarios. Some scenarios have been done to calculate the surface runoff volume of the whole Wadi Al Dawasir basin and calibrated the results based upon the paleo-flood measurement of Wadi Ranyah sub-basin. The calculated volume of Wadi Al Dawasir basin ranges from 4.8 BCM to 27.4 BCM for 2- and 100-year return periods, respectively.