Hydrogeochemical investigation and isotopic composition as tracers of ground water recharge in Chitipa district, Malawi

This study evaluated the hydrogeochemistry and stable isotopic composition of groundwater in Chitipa District, Malawi and made an assessment of seasonal recharge dynamics. Groundwater samples were collected during both dry and rainy seasons from 25 randomly selected boreholes across the Traditional Authorities Mwaulambya and Misuku. Quantitative analysis using SPSS (version 20) revealed significant seasonal variation (p < 0.05) in electrical conductivity (EC) ranging from 202–308 µS/cm and nitrate levels rising from 0.7 to 68.6 mg/L between seasons, chloride (Cl⁻), bicarbonate (HCO₃⁻), potassium (K⁺), and calcium (Ca2⁺), while pH, sodium (Na⁺), sulfate (SO₄2⁻), and magnesium (Mg2⁺) remained statistically unchanged (p > 0.05). Piper diagrams and ionic dominance sequences indicated mixed groundwater types mainly Ca-Na-HCO₃ and Ca-Mg-SO₄. Dominant ions across seasons were Na⁺ > Mg2⁺ > Ca2⁺ > K⁺ (cations) and HCO₃⁻ > Cl⁻ > SO₄2⁻ > NO₃⁻ (anions), all within Malawi Standards. The findings suggest that seasonal recharge is influenced by precipitation and land-use practices. To protect groundwater quality, the study recommends improved sanitation infrastructure, sustainable agricultural practices, and intensified afforestation to enhance aquifer recharge.