Crisis Beneath the Sands: Groundwater Degradation and Health Risks in the Northeastern Algerian Sahara – The Case of Oued Souf Valley

Abstract

The Oued Souf Valley in southern Algeria, part of the vast Sahara, is confronting a severe groundwater crisis driven by overexploitation, human-induced pollution, and climate variability. This study presents an extensive assessment of hydrochemical, bacteriological, and heavy metal contamination across three major aquifers: the shallow phreatic, complex terminal, and continental intercalary aquifers. Results from 58 monitoring wells and detailed sample analyses reveal alarming contamination levels in the phreatic aquifer, with electrical conductivity up to 7500 μS/cm, nitrate concentrations exceeding 150 mg/L, and high levels of aluminum, lead, and manganese. All phreatic samples showed very high pollution levels based on the Groundwater Pollution Index (GPI). Spatial analysis linked contamination patterns to intensive agriculture and urban expansion. Deeper aquifers displayed lower contamination but still frequently exceeded WHO standards for drinking water and irrigation due to high salinity and mineralization. Health risk assessments revealed hazard index (HI) values exceeding 1 for adults in 8 samples and for children in all samples, highlighting significant risks from long-term exposure to metals. Geostatistical modeling showed fluctuating groundwater levels between 2008 and 2021, driven by human activity and infrastructure failures. While ecological risk from heavy metals was generally low, localized samples showed considerable or high risk, especially due to lead contamination. The findings underscore the urgent need for integrated water management, stricter pollution controls, improved infrastructure, and targeted public health interventions to safeguard this vulnerable region’s water resources and its population’s health.