Environmental impact of the barrage construction on groundwater

Groundwater is among the most vital sources of freshwater, providing the primary supply for human consumption and for agricultural and industrial use. Although the construction of barrages enhances resource management and alleviates droughts and floods amid escalating population growth, it affects groundwater quantity and quality. As the most significant multipurpose water project on the Nile River, the new Assiut Barrage is crucial to the country's food self-sufficiency and to the livelihoods of nearly 6 million people. However, the environmental impacts of the new barrage on groundwater in the surrounding area are unclear. In this study, we monitored groundwater levels at 55 wells over 12 years, both before and during barrage construction, to clearly illustrate the barrage's effects on groundwater levels. Moreover, groundwater quality and associated health risks (HRA) were evaluated. This research demonstrated that the presence of water in a barrage's reservoir affects the groundwater level, particularly in the surrounding area. During the construction of the new barrage, groundwater levels declined in the upstream observation wells while increasing in the downstream districts. This fluctuation could be due to excessive groundwater withdrawals for irrigation in the upstream areas, while levels decrease in the downstream areas because of their urban rather than agricultural character. According to the groundwater quality index (GQI) model, 75% of upstream groundwater samples and 66.7% of downstream samples fall into the good category for irrigation. Our HRA findings indicated that both carcinogenic and non-carcinogenic risks from dermal exposure to heavy metals (HMs) across all studied groundwater wells are negligible. This study provides a clear picture of the impacts of barrages on groundwater, with implications for similar conditions worldwide, including arid and semi-arid regions.