WATERSHED MODELING FOR WATER RESOURCE MANAGEMENT IN TWO BASINS OF NORTHWESTERN COASTAL ZONE, EGYPT

Water resources in the coastal area of Egypt are very limited in magnitude as they originate mainly from the rainfall of the winter season. This water scarcity problem is the major constraint for the developmental activities in the area. Runoff Water Harvesting (RWH) is one of the most effective solutions to overcome this problem. The main objective of this research is to use the watershed modeling system (WMS) approach involving the integration of Digital Elevation Model (DEM), meteorological data, land use/land cover, soil type and hydrological model to assess the potentiality of two important basins (Umm Ashtan and Umm El-Rakham) near the city of Mersa Matrouh for water resources management and agricultural development activities. The study aimed also to predict annual peak flow and runoff water volume, as well as the 100-, 50-, 25-, 10-, and 5-year return periods. Results indicated that, the study area includes eight landform units namely: coastal plain, sloping area, escarpment, coarse valley inner, coarse valley outer, low piedmont, moderately high piedmont and high piedmont. Results showed also that Umm Ashtan basin is characterized by larger basin area (105.8 km2), basin length of 34.3 km, perimeter of 119.4 km, and gentle slope (0.024 m/m) as compared with Umm El-Rakham basin. Three types of land use/land cover in the studied basins were identified, namely: agricultural land, barren land and urban. The land use/land cover types represent 16.4, 83.59 and 0.21% of Um Ashatan basin and 34.0, 64.0 and 2.0% of Um Al-Rakham basin, respectively. The Curve Number (CN) average values are 73.8 and 76.15 for of Umm Ashtan and Umm El-Rakham basins, respectively. The annual runoff water volumes are 66150.0 m3 and 49896.7 m3 for the first and second basins, respectively. However, the annual infiltration volumes are 41398.0 m3 and 26450.6 m3 for the first and second basins, respectively. The peak flow of the 100-, 50-, 25-, 10-, and 5-year return periods are 73.53, 49.28, 30.68, 13.58 and 5.46 m3/s for the first basin and 75.82, 49.96, 30.41, 12.82 and 4.77 m3/s for the second basin, respectively. The Runoff volume of the 100-, 50-, 25-, 10-, and 5-year return periods are 3667.25?103, 2490.05?103, 1577.16?103, 721.47?103 and 300.63?103 m3 for the first basin and 4618.33?103, 3071.74?103, 1891.25?103, 813.18?103 and 306.49?103 m3 for the second basin, respectively. The two basins (Umm Ashtan and Umm El-Rakham) can be recommended to have priority for rainwater harvesting with agriculture potential benefits within the Northwestern coast of Egypt.