Assessment of Groundwater Quality Using the Water Quality Index (WQI) and Nitrate Pollution Index (NPI), in the El-Oued Region (South-East Algeria)

Abstract

Groundwater, serving critical requirements for both drinking and irrigation, is a vital and irreplaceable resource. The objective of this paper is to assess the quality of unconfined aquifers in the El-Oued region located in the northern Sahara of Algeria. The assessment employs two practical analysis models, namely the Water Quality Index (WQI) and the Nitrate Pollution Index (NPI), with a focus on irrigation and domestic water use. In this investigation, an extensive set of 113 samples was gathered from diverse locations to undergo analysis and assessment.

The WQI findings indicate that 38% of the samples exhibit very poor to unsafe water quality, characterized by strong to very strong salinity unfit for all uses. Conversely, 62% of the study area samples demonstrate good water quality with moderate salinity suitable for both domestic and irrigation purposes.

The Nitrate Pollution Index (NPI) was calculated to assess the level of nitrate (NO3) contamination in the El-Oued region water’s. According to the NPI results, 24% of the samples indicate high to very high pollution levels unsuitable for any use, while 76% of the study area samples exhibit low to moderate pollution, making them suitable for irrigation purposes. The elevated nitrate pollution in the unconfined aquifer observed in urban areas is attributed to human activities, such as improper waste disposal in open areas and infiltration of sewage.