Assessment of groundwater quality for drinking and sustainable irrigation using hydrogeochemical indices and multiple linear regression in the Bawku West District, Ghana

Abstract

Groundwater sustains domestic supply and smallholder agriculture across the semi‑arid Bawku West District of Ghana, yet climate variability, rising demand, and expanding agrochemical use increasingly threaten its quality and long‑term usability. Despite its importance in the district, limited characterization of spatial groundwater quality patterns and hydrogeochemical controls constrains effective resource management. This study applied hydrochemical graphing, kriging‑based geospatial mapping, multivariate statistics, and multiple linear regression (MLR) to analyse 69 borehole samples and evaluate suitability for drinking and irrigation. Major ions occur in the order Na⁺ > K⁺ > Mg 2 ⁺ > Ca 2 ⁺ and HCO₃⁻ > SO₄ 2 ⁻ > Cl⁻, with Na–HCO₃ facies dominating 41.4% of samples, indicating silicate weathering and rock–water interaction as primary geogenic controls, alongside localized anthropogenic inputs of nitrate and sulphate. Most samples comply with WHO drinking‑water standards, with limited exceedances for fluoride (2.9%) and nitrate (15.9%). Irrigation assessment reveals that although 98.6% of samples exhibit excellent SAR, irrigation suitability is largely doubtful to unsuitable based on Na% (92.8%) and magnesium ratio (85.5%), reflecting relative sodium and magnesium enrichment that may degrade soil structure under prolonged irrigation. The MLR employed a Groundwater Quality Index derived from standardized physicochemical and ionic parameters and demonstrated strong performance (R 2 = 0.88; adjusted R 2 = 0.86; p < 2.2 × 10⁻ 1 ⁶), indicating that TDS and Ca 2 ⁺ significantly influence groundwater quality, while elevated TDS indicates mineralization‑driven deterioration and HCO₃⁻ shows a negative buffering effect. The study recommends water mixing, targeted treatment, salt‑tolerant crops, and controlled agrochemical use to support resilient groundwater management.