Application of isotope techniques to groundwater resources management in the North-Western part of the Volta River Basin of Ghana. 

Priscilla Lartsey

In the North-Western part of the Volta River Basin of Ghana, population has been projected to rise along with agricultural activities. In addition, climate models have predicted an increase in temperatures and decrease in annual precipitation, for which their effects on the quality and quantity on groundwater resources in the area remain uncertain. This project therefore seeks to evaluate the quality and quantity of groundwater resources in the study area, using isotope techniques and conventional methods. The objectives of this study includes (1) establishing the origin and mechanism of recharge using hydrochemistry, stable isotopes of water, tritium and water table fluctuation, (2) Investigating surface water- groundwater interaction using the stable isotopes and radon mass balance, (3) Exploring the use of leaching experiments to delineate rock-water interactions that influence groundwater chemistry in the study area, (4) Investigating nitrate contamination of groundwater using ¹⁵N and ¹⁸O of nitrate. To meet the set objectives, 97 groundwater samples, 8 surface water samples and 5 rock samples were obtained from the study area. Piezometers were installed into two monitoring wells and a rain sampler also installed in the study area to collect rainfall. Water samples were analysed for chemistry, stable isotopes of water, tritium, radon isotope and nitrogen- 15 isotopes. Rocks samples were prepared for thin sections, X-Ray Florescence, X-Ray Diffraction, and a portion used for the leaching experiment. The research is part of an IAEA technical cooperation project, in which Ghana is working in collaboration with Burkina Faso, Togo and Benin in the Volta basin to understand the aquifer systems and to collaborate towards the management of the aquifers for sustainable groundwater supply.