Classification and quality of groundwater supplies in the Lower Shire Valley, Malawi – Part 1: Physico-chemical quality of borehole water supplies in Chikhwawa, Malawi

Abstract

This paper presents data on the physico-chemical quality of groundwater supplies in Chikhwawa, Malawi. Eighty-four water samples were collected and analysed for a range of chemical constituents (Al, As, Ca, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb, Se, V, Zn, K, Na,Cl^-, F^-, NO₃^-, SO₄^2-), pH, temperature, electrical conductivity and turbidity, from 28 boreholes located in 25 remote, rural villages (n=3 per village) distributed along the east (n=15) and west (n=10) banks of the Shire River. Samples were collected every 2 months during the wet season, over a period of 5 months (December to April). Results were compared with national (Malawi Bureau of Standards Maximum Permissible Levels (MBS MPL)) and international (World Health Organization Guideline Values (WHO GV)) drinking-water standards. In general, most parameters complied with the Malawi Bureau of Standards Maximum Permissible Levels (MBS MPL) for borehole water supplies. The MBS MPL standards for iron, sodium and nitrate were slightly exceed at a few boreholes, technically rendering the water supply unwholesome but not necessarily unfit for human consumption. In contrast, significantly high nitrate (< 200 mg/ℓ) and fluoride (< 5 mg/ℓ) concentrations at levels which constitute a significant risk to the health of the consumer were detected in borehole samples in a number of villages and warrant further investigation. Water committee members complained of problems associated with taste (saltiness or bitterness) and appearance (discoloured water) primarily on the west bank, presumably as a result of the high sodium and chloride levels, and precipitation of soluble iron and manganese, respectively. This resulted in some water collectors reverting to the use of surface water sources to obtain drinking-water, a practice which should be dissuaded through the education of water and village health committees.

Keywords: Wholesomeness, fitness for human consumption, borehole water quality, Malawi