Application of oxygen-18 and deuterium for investigating the origin of groundwater in connection with a dam project in Zambia

A study on the origin of groundwaters around the Itezhitezhi storage dam in Zambia was performed with the aid of analyses of the environmental isotopes 18O and D at the Laboratory of Mass Spectrometry, Division of Hydrology at the University of Uppsala. After the reservoir was constructed and filled a number of springs with warm water emerged in an area downstream from the dam. Analyses of 18O indicated the existence of a lower groundwater aquifer different in origin to the upper groundwater. A continued programme to study the variation of 18O contents at selected water-sampling points has shown that there is no rapid hydraulic connection between the recent water in the reservoir and the artesian water in the bedrock downstream from the dam. Chemical investigations and 14C age dating confirmed the conclusions drawn from the 18O analysis that the artesian water originated from an ancient epoch. Calculations on calcite saturation and original temperatures of the artesian water suggest the existence of well-separated groundwater aquifers in the area. (author)