REGIONAL AND LOCAL CONTROLS ON GROUNDWATER QUALITY IN SIERRA LEONE, WEST AFRICA

Measuring and mapping out water quality is quickly becoming a top priority in many African countries due to increasing pressure on water resources from climate change and growing population. The Government of Sierra Leone (West Africa) has recently received foreign investment in order to improve the water sector and the quality of drinking water services around the country. The goal of this study is to process groundwater quality data collected from various sources around the country and map out chemical contaminants that can be particularly detrimental to human health upon consumption.

Well data from over 475 boreholes (> 30 m deep) around Sierra Leone was compiled from third-party sources, including local drilling companies, government/district offices and the World Health Organization. Chemical data from 86 of those well locations were found relevant and analyzed to find spatial correlations between chemical parameters (such as pH, fecal coliform counts and trace metal levels) and thematic features (proximity to major roads, land use, human settlement density, population density). These correlations were then created into subsequent maps exhibiting a visual interrelationship between the aforementioned variables. A generalized danger map for chemical contamination was generated for each well location and extrapolated for the surrounding regions.

Preliminary results suggest that 1) biological contamination shows a positive spatial correlation with predominantly agricultural land-uses and a fair dependency on human settlement density, 2) physicochemical parameters (TDS, turbidity) are likely associated with the proximity of major transportation axes, and 3) trace metals (copper, iron, manganese) suggest a contamination from natural (geologic) origin.

These results highlighted regions of the country where groundwater safety should be further investigated and where appropriate management plans need to be developed in order to make it safer for human consumption.