Modeling the Partitioning of Precipitation over the Almadinah Watershed, Saudi Arabia: An Integrated Approach

English Abstract:

Assessment and development of freshwater resources remain the main and the only key to sustain the Kingdom of Saudi Arabia growing population and increasing water consumption. An integrated (remote sensing, GIS, and modeling) approach was applied to spatially delineate the recharge areas of, and model the precipitation of precipitation over, the Almadinah watershed, the largest (area: ~108,000 km2) watershed in the Kingdome of Saudi Arabia, during the past three decades. The Soil Water Assessment Tool (SWAT) was used to estimate the partitioning of precipitation into runoff, recharge, and evaporation. SWAT model inputs were generated as follows: (1) daily rainfall data extracted from the Tropical Rainfall Measuring Mission (TRMM) data which is calibrated against rain gauges measurements; (2) soil data were extracted from the geologic maps generated by Saudi Geological Survey; (3) land use maps extracted from the U.S. Geological Survey (USGS) 1-km global Land Use and Land Cover database; (4) topography data were generated from a mosaic of Shuttle Radar Topography Mission (SRTM; 90 m spatial resolution) data; and (5) other climatic parameters including solar radiation, wind speed, air temperature, and relative humidity were obtained from the Climate Forecast System Reanalysis (CFSR) database. SWAT model was calibrated against the discharge data extracted from the archival runoff datasets. The average annual modeling results over the Almadinah watershed through the period from 1980 to 2010 revealed: (1) rainfall was estimated at 58 mm; (2) stream flow were estimated at 19.1 mm (33% of the rainfall); (3) the potential recharge was estimated at 7.2 mm (12.5% of the rainfall); and (4) initial losses is estimated at 31.3 mm (54% of the rainfall). Our results invite the deployment of technical projects such as dam construction and wells installation for groundwater extraction within the Almadinah watershed.