Water Quality Features and Metal Pollution in Wadi El Rayan Lakes, Egypt

Located in the Western Desert of Egypt, 125 kilometers southwest of Cairo, the Wadi El-Rayan protected area encompasses two man-made aquatic ecosystems, known as Wadi El-Rayan lakes. These lakes play a crucial role in regional irrigation and have an extreme economical importance in fishing, sustained solely by agricultural runoff of El-Wadi drain. This study aimed to comprehensively assess the water quality status and heavy metal pollution (Fe, Cu, Cd, Pb, Cr, Co, Ni, Zn, Al, Mn) in the Wadi El-Rayan lakes by evaluating physicochemical characteristics, heavy metal concentrations, and applying established water quality and metal pollution indices. Water samples were collected seasonally in 2021 from winter to autumn. Our data declared a significant elevation in organic contamination; nutrient salts, and chlorophyll-a in the upper lake compared to the lower lake. Conversely, the lower lake exhibited a fifteen-fold rise in salinity. This salinity upsurge, averaging 31.68%, limits the suitability of the lower lake for irrigation. according to the Canadian Water Quality Index (CWQI) classification, the upper lake was identified as "marginal" across all sites for aquatic organisms and "fair" for irrigation, while the lower lake was "fair" for fish habitat. The Oregon Water Quality Index (OWQI) indicated critically poor water quality in both lakes. Pollution and heavy metal pollution indices (PI and HPI) underscored varying degrees of metal contamination, particularly concerning aquatic life in both lakes. According to the Pollution Index (PI) of individual metals, Co displayed serious pollution effects, while Pb showed slight pollution effects across all sites. While, Cu showed slight local effect on the area affected by El-Wadi Drain. Other metals showed no significant pollution. This study raises a critical alarm regarding the escalating pollution, advocating for immediate intervention to mitigate the degradation of these vital aquatic resources, preventing a scenario reminiscent of Lake Qarun's ecological transformation.