<p>Water quality in the Niger Delta is shaped by complex natural and anthropogenic factors. This study investigated the physicochemical characteristics, ionic composition, drinking/irrigation water quality indices, and hydrogeochemical facies of water (111 groundwater and 2 surface water) from 22 communities in the Niger Delta following standard methods. Results showed acidic pH (4.33 ± 0.12–7.44 ± 0.41) and elevated magnesium (61.20 ± 2.00–83.00 ± 0.00&#xa0;mg/L), not meeting WHO, SON and NESREA limits. Phosphate levels (0.66 ± 0.06–1.51 ± 0.16&#xa0;mg/L) surpassed the ecological threshold (0.15&#xa0;mg/L), indicating anthropogenic pollution and eutrophication risk. Water Quality Index classified all samples (108.48–169.04) as poor. Irrigation indices (SAR, RSC, KR, PI, PS, CBR, %Na, SSP, BH) rated the water as generally suitable, except Magnesium Adsorption Ratio (&gt; 50 in − all samples) and Corrosivity Ratio (elevated in 36% of samples), which suggest long-term soil permeability and water infrastructure risks. Ionic order was Ca²⁺ &gt; Mg²⁺ &gt; Na⁺ &gt; K⁺ and HCO₃⁻ &gt; SO₄²⁻ &gt; Cl⁻ &gt; PO₄³⁻ &gt; CO₃²⁻. Geochemical analysis (Piper, Chadha, Durov, Stiff diagrams) indicated Ca-Mg-HCO₃ dominance from carbonate weathering via rock-water interaction (Gibbs plot) with reverse ion exchange as the main process (CAI, CAII). The Hydrochemical Facies Evolution Diagram showed mixed facies, while Chernoff face plots revealed anomalous chloride enrichment in 35 samples, influencing Schoeller and Gaillardet interpretations toward silicate weathering and evaporite dissolution. Principal Component Analysis identified TDS, HCO₃⁻, Na⁺, Mg²⁺ and Cl⁻ as key quality determinants, highlighting synergistic degradation from natural processes and human activities. Targeted pollution control, corrosion-resistant infrastructure, and sustained monitoring are needed to protect regional water resources.</p>