Decoding multidimensional water quality in arid industrial lakes: a comprehensive CCME-WQI, HPI, and GIS-based evaluation of the Arab al-Ulayqat system

Effective water quality management is crucial in arid regions, where inland water systems are highly vulnerable to anthropogenic pressure and climatic stress. This study aimed to assess water quality in Egypt’s Arab al-Ulayqat Lakes using physicochemical, microbiological, heavy-metal, multi-index, and GIS-based analyses to identify pollution levels, water-use suitability, and contamination hotspots. Ten sites were sampled in spring 2025 and analyzed for 36 physicochemical, microbiological, and heavy-metal parameters. Water suitability was evaluated using Canadian Council of Ministers of the Environment Water Quality Index (CCME-WQI), the Heavy Metal Pollution Index (HPI), irrigation indices, and industrial scaling/corrosion indices, while spatial patterns were mapped using Geographic Information System (GIS)-based Inverse Distance Weighted (IDW) interpolation. Results revealed severe and spatially heterogeneous deterioration. Salinity was extreme, with total dissolved solids (TDS) of 451–18,730 mg/L and electrical conductivity (EC) of 705–29,300 µS/cm. Turbidity ranged from 2.56 to 661 NTU, while organic pollution was substantial (biochemical oxygen demand (BOD) 6–20 mg/L; chemical oxygen demand (COD) 14–248 mg/L; mean COD/BOD ratio = 4.73), indicating dominance of poorly biodegradable contaminants. Nutrient enrichment was pronounced (total nitrogen (TN) 1.41–64.87 mg/L; total phosphorus (TP) 0.35–13.54 mg/L), confirming advanced eutrophication risk. Microbial contamination was substantial, with total coliforms up to 5.5 × 10⁵ CFU/100 mL and fecal coliforms up to 7.9 × 10⁴ CFU/100 mL. Heavy-metal pollution was also significant, with HPI values of 63.51–301.69 and an average of 132.72, while S7–S10 represented the main heavy-metal hotspot zone. Spatial assessment showed that only S2 and S5 achieved Good drinking-water status, only S2 and S5 were Marginal for aquatic life, and irrigation suitability ranged from Good (S2–S5) to Poor (S6). These findings indicate combined impacts from industrial discharge, agricultural runoff, domestic wastewater, and evaporative concentration. The study provides baseline data and a decision-support framework for targeted remediation, monitoring, and sustainable management of arid-region lake systems.