Using Hydrochemical And Isotopic Tracers to Assess the Impact of Anthropogenic Activities on Groundwater Quality in Bongo And Kassena Nankana West Districts in Upper East Region of Ghana

Abstract

The population within Bongo and Kassena Nankana West Districts, in the Upper East Region of Ghana is estimated to be about 84,545 and 70,667, respectively. An estimate of about 80% of the population depends on groundwater for domestic and agricultural purposes. However, groundwater resources in the Districts is at risk due to anthropogenic activities such as rapid increase in irrigation activities and animals rearing, open defecation and uncontrolled disposal of animal droppings, improper land use, waste disposal, and illegal mining activities. “This study was carried out to use hydrochemical and isotopic tracers to assess the impact of anthropogenic activities on groundwater quality in the study areas. The study employed hydrochemistry and isotopic techniques to assess the chemical quality of groundwater in the study areas. A total of sixty-four (64) boreholes were sampled from the study areas for the study. The samples were analysed in-situ for pH, conductivity and salinity using a HACH potable meter; and bicarbonate using a titrimetry. Analytical methods employed for the determination of major and minor ions were (Na+ and K+) complexometric titration (Ca2+) and (F-, Cl-, NO3 -, PO4 3-, and SO4 2-). Atomic absorption spectrometry was used for the determination of Mg2+ and heavy metals (Fe, Mn and As). Stable isotope of 2H and 18O composition of the water samples were determined using Liquid-Water stable isotope analyser [Off-Axis Integrated Cavity Output Spectroscopy (off axis ICOS) via Laser Absorption]. In general, majority of the ions are within the permissible limit for drinking purpose except few locations in the study areas. The Gibbs Diagram, the Piper Trilinear Diagram and the Hierarchical Cluster Analysis reveal different degrees of water-rock interaction or mineralization and are consequence of silicate weathering and silicate mineral dissolution, cation exchange and to a lesser extent University of Ghana http://ugspace.ug.edu.gh vi fertilizer application. Based on the Water Quality Index (WQI) classification, the majority of the samples fall under excellent to good water category and suitable for drinking water purposes, except for groundwater in few areas which showed deteriorating water quality. The stable isotopes composition implies, there has been fractionated before recharge”. Since, the values deviate towards the positive valves.