Groundwater quality assessment in south valley (Egypt) using multivariate and hydrochemical approaches

Abstract

To address freshwater scarcity, the Egyptian government has started mega developmental projects, such as the Southern Valley Development Project (SVDP), which utilizes groundwater resources to support new communities and agricultural projects. To ensure the suitability of water resources therein, water samples were collected from 19 wells distributed across the SVDP region. These samples were analyzed for their physicochemical characteristics. An integrated comprehensive evaluation was then followed, combining geochemical tools (Piper plots and Gibbs & Chadha diagrams), principal component analysis (PCA), human risk assessment, and water quality indices (WQIs), and the results revealed that the groundwater mineral composition was mainly controlled by rock water interfaces, especially silicate and carbonate weathering, though some wells were affected by saline intrusion. The chemical composition in 58% of wells was dominated by Na-HCO₃ water. Three key components were identified by PCA: natural rock weathering (55% variance, high Na⁺/Cl⁻/SO₄²⁻), agricultural pollution (18%, NO₃⁻/PO₄³⁻), and bicarbonate enrichment (12%, HCO₃⁻). Most water samples showed medium to high salinity hazards (C2-C3) but low sodicity (SAR < 10), though high RSC warned sodium buildup. Although, most potentially toxic elements were within safe limits (HI < 1), elevated Fe (exceeding WHO guidelines with HI > 1) and localized Pb spikes posed health risks, especially for children if not properly untreated. Thereafter, groundwater samples were evaluated for suitability for both drinking (DWQI) and irrigation (IWQI) purposes using the multivariate analysis model. Water quality indices classified 88% of samples as moderately safe for drinking (WHO) while most water samples can be classified as “good” for irrigation (FAO), except S7/S15/S18. The findings underscore the urgent need for localized groundwater management strategies which aligned with Egypt’s 2030 Water Strategy and the UN Sustainable Development Goals.