Assessment of groundwater quality in shallow wells within the southern districts of Malawi

Abstract

Lack of safe drinking water is a major problem in developing countries. Within Africa most people rely mainly on local groundwater sources for their water needs. These can be deep boreholes or shallow wells, the latter are normally found in poorer communities as they are the least expensive to construct. Over time water from these sources can be contaminated leading to fatal consequences. Previous monitoring of the quality of water from boreholes and shallow wells have been irregular, with the focus being mainly on boreholes. Information on seasonal water quality changes in shallow wells used by rural communities in Malawi has generally been lacking. A study was conducted from 2006 to 2007 to determine the quality of water from shallow wells in three districts in southern Malawi namely, Balaka, Chikwawa and Zomba districts. Water samples from 21 covered and five open shallow wells were analysed for chemical, microbiological and physical parameters using a portable water testing kit. Sampling was carried out at four different times of the year i.e. in August and October 2006 (dry season) and February and April 2007 (wet season). Microbiological data indicated that around 80% of the samples, obtained from the covered wells, failed to meet safe drinking water limits, set by World Health Organisation guidelines and Malawi Bureau of Standards, of zero total and faecal colony forming units (cfu)/100 ml. Values in excess of 1000 cfu/100 ml were noted in 10% of the samples, indicating gross contamination and the probability of pathogens being present. Contamination levels were higher during the wet season than the dry season in all three districts. Arsenic, ammonia, nitrate, nitrite and sulphate were all within the acceptable limits. Elevated levels of hardness, turbidity were noted in certain wells.