Abstract

The study focused on Likangala and Domasi Irrigation Schemes which were constructed in the 1960s along the coast of Lake Chilwa, a saline endorheic lake characterized by both regulated and unregulated cultivation. Water for irrigation comes from rivers whose surface water quality has been reported as contaminated. Overpopulation and water scarcity have affected residents of the two irrigation schemes to use groundwater as the only source of drinking water. The study was carried out toexplain the chemistry of groundwater and evaluate its suitability for drinking and irrigation purposes particularly during the dry season. The dominance of cations in both Domasi and Likangala Irrigation Schemes was in the order Na > Ca > Mg > K. For anions, the order for Domasi Irrigation Scheme was HCO3 > Cl > CO3 > SO4 >NO3 > F while that for Likangala Irrigation Scheme was Cl > HCO3 > CO3 > SO4 >NO3 > F. The study revealed that groundwater for the study area was predominantly of sodium bicarbonate type due to silicate weathering, cation exchange and agricultural influence. Based on the integrated drinking water quality index, 50% and 61.5% of the water points in Domasi and Likangala Irrigation Schemes were unsuitable for drinking purposes and some communities should be provided with alternative water sources. The main triggers for water unsuitability included elevated levels of carbonates, bicarbonates, turbidity, chloride and manganese. For both irrigation schemes, the total hazard indices (THI) were however within acceptable health risks for adults. All the water points showed that the water is suitable for irrigation purposes, with about 79% belonging to the moderate - excellent category. Therefore, there is a need to mechanize the abstraction of groundwater for irrigation during the dry season to maximize annual yield.

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School	: School of Natural and Applied Sciences
Issued Date	: 2024

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