Abstract
The Copperbelt Province of Zambia is marked by extensive surface water contamination as a result of heavy mining operations in the province over the past century. Both the World Bank (2009) and Republic of Zambia and Federal Republic of Germany (2007) have advised that Copperbelt communities turn to groundwater fields for drinking, domestic and irrigation water. Focusing on the city of Ndola, this research assesses the state of water provision in the city and the hydrogeochemcial viability of these resources in providing safe drinking, domestic and irrigation water for local communities. Water samples were collected from surface waters, shallow hand dug wells, and boreholes over a two-month period from April-June 2013. In-field measurements of pH, EC, Eh, temperature, and total coliform concentrations were taken, along with key informant interviews and local water-user questionnaire surveys. Water samples were analysed for a range of heavy metals, both in the total and dissolved forms, as well as dissolved cations. Statistical analysis of water quality data, and coding of key informant and water-user data highlighted key trends, differences, concerns, and challenges within the water supply systems of Ndola. Surface water contamination is evident in Ndola (primarily aluminium and total coliforms), whereby local users understand this and have turned from using these sources. However, access and the affordability of municipal supply as an alternative to surface waters are extremely limited in Ndola, forcing the majority of residents to rely on shallow wells. While distinct differences in water quality were observed between surface water and groundwater quality, shallow wells are not safe for human consumption (with concentrations of aluminium and total coliform exceeding recommended maximum values), primarily due to the lack of well protection and their vulnerability to contamination via surface water interactions and direct ingress from overland runoff. Borehole wells are protected from contamination due to their distance from the surface and subsurface filtration removing contaminants as water percolates through the phreatic zone. There was considerable spatial variation in water quality across the city, which is attributed primarily to variations in subsurface lithology and its role in metal mobility. For example, contamination was minimal in the dolomite-limestone areas, which is likely attributable to chemical buffering due to naturally high pH and hardness concentrations in dolomite aquifers. Furthermore, shallow wells in granite-gneiss areas were found to have lower levels of contamination, which was interpreted as a function of the low recharge rates into these rock types. Overall the groundwater resource is suitable for drinking and further development of this resource would substantially improve local access to safe drinking, domestic and irrigation water. However, the current reliance on shallow wells within informal communities needs to be urgently addressed, both to protect the health of those consuming this water and to protect the shallow aquifers from systemic contamination from pit latrines and poor well protection.