Abstract
Groundwater is the principal water resource supporting pasture-based livestock production in the arid Mangystau and Atyrau regions of western Kazakhstan, where permanent surface-water availability is limited. This study integrated field surveys of groundwater infrastructure with hydrochemical analyses of 36 groundwater samples (24 from Mangystau and 12 from Atyrau) to evaluate groundwater quality, livestock-watering suitability, and the practical usability of existing water points. Mineralization ranged from 281 to 10,298 mg/L, demonstrating substantial source-level and within-region variability. Total mineralization did not differ significantly between the sampled sources of Mangystau and Atyrau. After correction for multiple regional comparisons, statistically significant differences were retained for sulfate and bicarbonate, with higher sulfate concentrations in Mangystau and higher bicarbonate concentrations in Atyrau. Ionic charge-balance assessment showed that 35 of 36 samples were within ±10%; one charge-imbalanced sample was excluded from charge-balance-dependent hydrochemical interpretation. Among the 35 QA/QC-accepted samples, mineralization was strongly associated with Na+ (Spearman ρ = 0.834, p = 5.06 × 10−10) and Cl− (ρ = 0.843, p = 2.08 × 10−10), while Na+ and Cl− showed very strong covariation (ρ = 0.952, p = 1.51 × 10−18). Together with a median molar Na/Cl ratio of 1.10 and the predominance of Na–Cl facies, these relationships are consistent with an important contribution from saline and evaporitic sedimentary materials to groundwater mineralization. Twelve sources contained ≥7000 mg/L TDS and require restricted, source-specific livestock use. Elevated nitrate and ammonium occurred at a subset of water points and are interpreted as localized water-quality concerns whose origin cannot be established from the present dataset. The results demonstrate that pasture-water management should prioritize source-specific groundwater-quality assessment, infrastructure maintenance, and sanitary protection rather than reliance on administrative-region averages alone.