Groundwater Evaluation in a Rain-Fed Likangala Irrigation Scheme in Malawi

Abstract

The Likangala Irrigation Scheme in Malawi was constructed in 1969 along the coast of Lake Chilwa in Malawi, a saline inland basin lake. Water for irrigation comes from a heavily polluted river which also passes through urban and peri-urban areas of Zomba District. Overpopulation and water scarcity due to climate change have pushed people to have permanent residence within and around the scheme. Groundwater, through boreholes and shallow wells, is the only source of drinking water. The aim of this study was to evaluate the chemistry of groundwater and evaluate its suitability for drinking and irrigation purposes in the Lake Chilwa Basin. WSeven Boreholes and six shallow wells were sampled from the study area. The levels of the abundance of the major ions were found to be in the order Na > Ca > Mg > K and Cl > HCO₃ > CO₃ > SO₄ >NO₃ > F. The study results suggest that the groundwater for the study area is predominantly of sodium-bicarbonate type, due to both silicate weathering, cation exchange and agriculture influence. The Water Quality Index (WQI) showed that 61.5% of the groundwater samples were unsuitable for drinking. Based on irrigation quality index model, there was no sample belonging to a rejection category from irrigation. The study further revealed that 23% of the samples require caution to be used for irrigation. However, there is need for a further studies to examine the soil chemistry of the scheme to identify other crops suitable for the area, besides rice.