Hydrogeological Investigation: A Case Study on the Groundwater Potential Assessment in the Hantebet Catchment, Tigray, Northern Ethiopia Nata Tadesse*, Berhane A. and K. Bheemalingeswara Department of Applied Geology, Faculty of Science and Technology, Mekelle University, Mekelle, Ethiopia [P.O. Box 1604, E-mail: [email protected]] ABSTRACT The Hantebet catchment, which is consists of a vast depressed area bounded by adjacent Highlands, is located in the Northern Ethiopia in the Tigray Regional State having an area of 24.4 km2. The major objective of this research work was to conduct a systematic hydrogeological study of the area which help for better understanding, and then proper and full exploitation of groundwater resources of the area. Extensive work was carried out by collecting pertinent primary data of the area in the field and secondary data from different offices. Different lithological boundaries, drainage patterns, morphological features and geological structures were traced from aerial photographs. The major lithological units in the basin are dolerite sills/dykes (45.2 %), shale (13.4 %), limestone (12 %), siltstone (0.5 %) and alluvial deposits (28.9 %). Stratigraphically, limestone is found at the base overlain by shale and followed by siltstone. The younger igneous intrusions of dolerite as a sill and dyke are exposed on the top part of the hills and plateaus. Alluvium with varying thickness is found overlying all these successions in the lowlands. The major structures observed in the area are extensional fractures such as joints, dykes, listric faults, karsts and primary beddings. These structures strongly control the groundwater movement of the area. The different rocks and unconsolidated sediments of the area which behave as aquifers have been classified on the basis of the type of permeability which they exhibit and the extent of the aquifer into localized aquifer with intergranular permeability, less extensive aquifer with fracture and karstic permeability and localized aquifers with fractured and intergranular permeability. Even though limestone and dolerites have a characteristics of being an aquifer due to the place where they are found they facilitate downward flow rather than being acting as a water bearing formation. Alluvial sediments, weathered and fractured shale, weathered and fractured marl, weathered and fractured sandstone, and weathered and fractured dolerite dykes that are found in the depressed area are important aquifers where groundwater can be developed. Any future development of groundwater should be concentrated on these types of formations in the middle of the downstream side of the basin. Later extent and vertical thickness of the different aquifers; the productivity of the respective aquifers; and, the presence of additional multilayer aquifers, their respective thickness and productivity are recommended to be investigated for a better understanding of the aquifers of the area and then for a better development of the groundwater in the area. Keywords: Aquifer, fault, fractures, groundwater, permeability.