HYDROGEOLOGIC AND MORPHOMETRIC STUDY FOR BADRA BASIN,WASIT GOVERNORATE

Abstract

This report is devoted to evaluate the groundwater in Badra Basin east of Iraq. The exposed rocks in this basin extend in age from Late Cretaceous to the Pliocene. The Quaternary sediments of alluvial fans and sheet runoff cover most the downstream parts and the vast syncline in the middle parts. From the structural point of view, Badra Basin is located within three structural zones, the Mesopotamia Foredeep Zone, Low Folded Zone and High Folded Zone. The study area is classified as a semiarid to arid region according to the aridity index. It is characterized by hot and dry summer and relatively cold winter with moderate rainfall. There is a significant variation in the climatic parameter between the basin upstream and downstream areas, where the annual rainfall and potential evaporation in Ilam meteorological station (upstream area) are 420 mm and 1525 mm, respectively, while in Badra station (downstream area) are 185 mm and 3127 mm, respectively. This variation is mainly due to the significant difference in the elevation above sea level between the upstream and downstream areas. The upstream area is characterized by the carbonate fractured aquifer, while the downstream area is characterized by the intergranular aquifer of the Quaternary alluvial fan sediments and the late Miocene and Pliocene clastic sediments. The general direction of the groundwater flow in the study area is from northeast to southwest. The groundwater type is variable from chloridic type to sulphatic type, where it is mainly chloridic near the Iraqi Iranian border as result of the returned irrigation water, due to the extensive use of groundwater in irrigating the farms in Mehran Plain in the Iranian side during summer season. In addition, the presence of springs discharging deep brine chloridic water along the main faults could be another reason of being the groundwater in chloridic type. The sulphatic type of groundwater belongs mainly to dissolving the Miocene evaporite rocks (gypsum and anhydrite). According to the total dissolved solids (TDS), the groundwater in the area is classified generally as moderately brackish to slightly brackish water. The groundwater is not suitable for human drinking, but it is commonly suitable for livestock. Regarding the high infiltration capacity of sediments, the groundwater in general can be used to irrigate the salt tolerant crops. Quarter of the wells is suitable for building and construction and industrial purposes and few wells are suitable for petroleum and chemical industry, while no well is suitable for food, cement and paper industries. The morphometric results showed that the Badra Basin is an elongated Basin with low drainage density (Dd) especially in the upstream area. This can be explained by the high permeable, erosion resistant, and fractured carbonate rock. However, the Dd in the downstream parts is relatively higher; where the exposed rocks there consist of clastic sediments belong to Late Miocene, Pliocene and Quaternary sediments. In spite of the low form factor which is an indicator of flatter peak of flow for longer duration, after each heavy rainstorm the main valley downstream being loaded with eroded sediments due to the high value of the relief ratio (Rh) and easily eroded sediments in the downstream area. This fact gives an answer for the question of “why most of the