Geology of Kota Kinabalu and its implications to groundwater potential

The increasing population in Kota Kinabalu is proportional to the demand for water resource. Groundwater is a primary concern because it is the most economical source of water supply. The main objectives of this paper are (1) to evaluate the groundwater resources in the study area, and (2) to study the effects of geology on groundwater. Kota Kinabalu is underlain by the Late Eocene-Lower Miocene Crocker Formation and Quaternary Alluvium. The Crocker Formation is composed of sandstone, shale and an interlayered sandstone-siltstone- shale sequence. The study area is controlled by heavy structural lineaments representing a complex history of folding, thrust, normal and wrench faulting. Movements along these structures strongly influence the geomorphology and groundwater distribution in Kota Kinabalu. The rocks within the fault zones are highly deformed, sheared, jointed, and fractured. The geology of the study area indicates that only the sandstone units of the Crocker Formation and Quaternary alluvium can be considered significant groundwater reservoirs. The aquifers within the study area can be divided into three major groups based on host rock and structural parameters, as follows (1) aquifers of Quaternary Alluvium, (2) aquifers within the fault zones, and (3) aquifers of the sandstone units of Crocker Formation. The chemical and physical analysis of the Kota Kinabalu groundwater suggest a meteoric origin and an alkaline type of water. Both the stratigraphic and structural settings favor a high potential groundwater resource in Kota Kinabalu. These settings facilitate the movement and circulation of groundwater within Crocker Formation and Quaternary Alluvium, affect the continuity of aquifers, enhance secondary permeability, as well as increase the storage capacities of the formations. Such settings also create confined and unconfined aquifer systems