Isotopic characterization of groundwater and surface water in the Keta Basin, Ghana

This paper presents the application of environmental isotopes (O-18/O-16, D/H and Sr-87/Sr-86) to groundwater and surface water studies with emphasis on saline groundwater in aquifers in the Keta Basin. Ghana. The isotopic compositions of oxygen and hydrogen of deep groundwater reveal small variations and plot close to the global meteoric water line. Shallow groundwater and surface water reveal considerably larger variations in the isotopic compositions and show pronounced evaporitic enrichment. The 87Sr/86Sr ratios of the groundwater and surface water primarily reflect the geology of the formations in the aquifers and the recharge areas. However, groundwater from a number of deep wells and dug wells in near-coastal aquifers is characterized by relatively high Cl contents. A significant marine influence in these aquifers is indicated by well-defined mixing lines for both strontium isotopes, hydrogen and oxygen isotopes with the isotopic composition of modern seawater as one end-member.