24th WaterNet/WARFSA/GWPSA Symposium
25-26 October 2023 | Zanzibar, Tanzania
Groundwater remains the most reliable source of groundwater supply for rural households, who constitute 80% of the population in Malawi. Nevertheless, groundwater resources are prone to contamination, a situation that poses a high risk of water related infection to end-users and the environment at large. The contamination of groundwater resources is a function of a wide range of natural and anthropogenic processes within the catchments and aquifers. An understanding of natural and anthropogenic hydrogeochemical processes affecting quality of groundwater is vital in the sustainable management of groundwater resources under the changing climatic pressures.
Therefore, this work sets out to study the hydrogeochemistry of groundwater in Salima and Lilongwe districts in Malawi to predetermine and locate usable groundwater supplies for effective future adaptation to changes in groundwater quality. A total of 60 randomly selected boreholes and shallow wells were sampled using standard sampling procedures. Levels of CO32- (mg/L), HCO3- (mg/L), Cl- (mg/L) were determined titrimetrically. Levels of were determined using uv/vis spectrophotometer. Levels of Na+ and K+ were determined by flame photometry. Levels of Ca2+ and Mg2+ were determined using atomic absorption spectrophotometer. Geochemists’ Workbench®️ Release software, Surfer Golden Graphics software, bivariate and Gibbs plots were used to model major hydrogeochemical processes. This study observed that a wide range of hydrogeochemical water types follows: Ca-Cl (32%), NaHCO3 (20%), Mg-Cl (8%), Na-Cl (30%) and Ca-HCO3 (4%). Rock-water interaction, evapoconcentration, reverse ion exchange processes and salt water intrusion were observed to be the major hydrogeochemical processes. The groundwater was observed to vary spatially and controlled by four PCs, which controlled 72.69% of the variations. Detailed hydrogeochemical modelling of groundwater quality is recommended for locating useable groundwater supplies and sustainable management of groundwater resources.
Keywords: Hydrogeochemical modelling; Groundwater; Geochemist Workbench; Water quality
