Effects of a semi-formal urban settlement on groundwater quality: Epworth (Zimbabwe): Case study and groundwater quality zoning

Abstract

Rapid urbanisation and lack of low cost accommodation in the City of Harare, Zimbabwe, led to a lot of people settling (formally or otherwise) on previously cultivated land in Epworth, south-east of the city. Groundwater quality in different parts of Epworth, a semi-formal settlement in Zimbabwe, was investigated. Water samples for water quality analysis were collected from 10 shallow boreholes and 20 shallow wells across the settlement. Results showed significantly elevated levels of nitrates and coliform bacteria in most parts of the settlement. Levels of coliforms were highest in the old parts of the settlement (>10,000 cfu). High nitrate levels (20–30 mg/l) can be related to more densely settled areas, with a higher density of pit latrines. The groundwater quality generally decreased downflow (to the south-east). Na, Zn, Cu, Co, Fe, PO 4 were also determined, of which only iron showed substantially high levels. Groundwater quality results were used to delineate parts of the settlement into water use zones. Three broad zones were defined: Zone 1 (water drinkable after boiling), Zone 2 (water for agricultural use only), and Zone 3 (water unsuitable for domestic or agricultural purposes). The results also showed that most parts of the settlement have no safe groundwater for human consumption and Zone 1 could be faced with high nitrate levels in future. It is too late to prevent contamination of groundwater in this settlement. As a cost-effective measure to reduce health risk, the local authority could consider the provision of a limited water supply, via communal taps, starting in those areas in Zones 2 and 3 except for the south-east where there area already communal taps. A health education campaign on the risks of drinking polluted groundwater in this settlement is also necessary. The development of a sewage system is an alternative although it is expensive with the current situation. Furthermore, although a proper sewage reticulation system would prevent further groundwater contamination, the levels of nitrate will remain high, until flushed by recharge.