MORPHOMETRIC ANALYSES OF WADI AL-AJEEJ DRAINAGE BASIN, USING GIS TECHNIQUE

Abstract

Wadi Al-Ajeej” drainage basin is one of the areas in the Al-Jazirah Province, experiencing shortage in water-resource in Iraq. Morphometric analyses are made in this study for “Wadi Al-Ajeej” drainage basin to support formulating plans, on the basis of the results, and to help in a better implementation. GIS techniques have been adopted to identify morphologic features and analyse their properties. Morphometric parameters such as linear, aerial and relief aspects of the drainage basin were computed and determined. The entire drainage basin of Wadi Al-Ajeej covers 3804.7 Km² with seventh order stream network, comprising three contiguous sub-basins; Al-Badee, Al-Khazrajia and Al-Hamal sub-basins which occupy 80% of the area in the northern and eastern parts of the basin. The drainage network of the three sub-basins in addition the entire Al-Ajeej basin are delineated using the Digital Elevation Model (DEM) 30 m resolution. The drainage network shows that the terrain exhibits dendritic, sub-parallel and trellis drainage patterns. Estimated drainage density is approximately 1.3 Km/Km² and has coarse drainage texture. The bifurcation ratio in all subbasins has experienced moderate structural disturbances, by “Tel-Hajar” subsurface extensional structure, that change the main streams flow from NNW – SSE to NNE – SSW. Al-Badee, Al-Khazrajia and Al-Ajeej subbasins are the highest relief ratios (17.2, 15.6, and 12.7 respectively), due to their high reliefs (1126 m, 966 m, and 1162 m respectively), while Al-Hamal subbasin has low relief ratio (2.14) due to its low relief (128 m). Drainage density results refer to excellent drainage basin (with moderate rates of infiltration and surface runoff) and coarse texture (indicate low erosion and high relief). The elongation ratio shows that three subbasins (Al-Badee, Al-Khazrajia and Al-Hamal) possesses an elongated shape pattern, but only Al-Ajeej subbasin seems to be close to a circular shape.