Variations in groundwater quality in protected and unprotected water sources of Murehwa district

Abstract

Target 7C of the Millennium Development Goals is aimed at halving the proportion of people without sustainable access to safe drinking water and basic sanitation by 2015 (UNDP, 2002). Therefore, implementation of water and sanitation projects in line with this target need to give due attention to measured water quality and assess if water is of acceptable standards. In this regard, an assessment of groundwater quality was carried out in three wards of Murehwa District in Zimbabwe in February and March 2011. Samples from 60 randomly selected ground water sources; 30 protected wells and 30 from unprotected wells were analysed for thermotolerant coliform, pH and turbidity parameters using a portable Delagua water testing kit. This was to find out whether there were significant differences in water quality levels in protected and unprotected wells during the wet season. A point interpolation (isotropic kriging) was used to determine the spatial variations of coliform levels in groundwater sources. Results indicated significant differences in coliform levels between protected and unprotected wells (p = 0.00). Coliform levels in almost 67% of the protected wells and all (100%) unprotected wells failed to meet the Standard Association of Zimbabwe guidelines of 0 CFU/100 ml (SAZ, 1997). Results also showed a significant (p = 0.016) difference in pH between the two water sources. There was no significant (p = 0.376) difference in the turbidity of the two water sources. Well depth was found to be negatively correlated with contamination levels in both protected (p = 0.028, r = - 0.5517)) and unprotected wells (p = 0.001, r = -0.589). Distance from pit latrine was negatively correlated with coliform level in unprotected wells, (r = -0.46, p = 0.0352). Slope angle was not significantly (p>0.05) correlated with coliform level in both water sources. Findings also showed that the concentration of coliform in groundwater was spatially autocorrelated up to 228.8 m. Results showed that both protected and unprotected wells were vulnerable to bacterial contamination