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The groundwater of wadi Djendjen plain (Jijel, North-East Algeria) have always been used as drinking water supply in the cities and the irrigation of agricultural lands.¶ This confers this aquifer, which has already been the subject of numerous hydrogeological studies, a particular interest in terms of qualitative and quantitative monitoring. Its exploitation is today encountering excessive salinity problems, evidenced by measurements of the electrical conductivity of the water and the alkalinisation of soils.¶ This degradation of the environment results, among others, from ion exchange which involves cations (sodium, calcium and magnesium), water / clay interaction as reflected by the sodium absorption ratio (SAR).¶Analyses on samples of groundwater destined for irrigation and the application of a geostatistical approach have enabled to map the most affected zones by this phenomenon.¶

Today, scientists are deeply concerned by the vulnerability of groundwater reservoirs to pollution. Relatively simple overlay and index methods can be used to produce groundwater vulnerability maps in geographic information system. In addition, this study deals with contamination from nonpoint sources. In this study, two such models, DRASTIC and GOD, were applied in the Jijel Plain area of northeast Algeria and compared with measured groundwater nitrate concentrations. This showed that results from DRASTIC were better than GOD, 69% correlation with nitrate compared to 56%. DRASTIC was better able to identify vulnerable zones along the river valleys. The DRASTIC model was then modified using the nitrate concentrations to optimize the rating score given within each parameter range and sensitivity analysis to change the weighting given for each parameter. These combined changes gave a final Pearson's correlation of 83% with nitrate. This showed that recharge, aquifer type, and topography were the key factors in controlling vulnerability to nitrate pollution., (© 2017, National Ground Water Association.)