Mapping and Assessment of Groundwater Quality in Ghardaia Region, Northern Sahara, Algeria

Abstract

This study assesses the quality of groundwater of the phreatic aquifer in Ghardaia, used locally for drinking water supply. Accomplished by mapping and analyzing physico-chemical parameters and their spatial distribution, as well as calculating a water quality index (WQI).

Ten groundwater wells were analyzed. Water samples collected in December 2023 were tested at the laboratory of Algerian water company (ADE) for eleven quality parameters. The Water Quality Index (WQI) was then calculated using ArcGIS mapping and WHO standards to assess overall water suitability.

The physicochemical analysis indicates that the groundwater   is generally slightly alkaline and weakly mineralized, suggesting good quality freshwater. However, most samples exhibit high hardness due to natural mineralization, with the Berriane and Selama–Sebseb wells exceeding the WHO limits for total hardness, as well as for magnesium and potassium. Elevated nitrate levels at the Djafar well (83.92 mg/L) suggest agricultural contamination. Spatial mapping reveals natural mineralization in the northern areas (Berriane) and nitrate pollution in areas close to agriculture and urban development, such as Noumerate. Overall, eight of the ten wells are of excellent quality (WQI = 5.03–17.57), while the quality of Selama–Sebseb and Laadira is lower, being classified as “good” and “poor”, respectively.

The study concludes that the groundwater in Ghardaia is generally of an excellent quality, with a WQI ranging from 5.03 to 17.57. Nevertheless, localized issues persist, including natural mineralization in the northern areas (Berriane) and nitrate pollution exceeding WHO limits near agricultural zones such as Noumerate.