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Evaluating and mapping the groundwater pollution susceptibility of the El Madher alluvial aquifer, Eastern Algeria, using the Drastic method Volume 12, issue 2, Juin 2001

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Département Science de la Terre, Université de Batna, rue Chahid-Boukhlouf, Batna 05000, Algérie.
  • Page(s) : 95-101
  • Published in: 2001

Groundwater pollution potential mapping enables identification of areas with a high risk of contamination, irrespective of the type of pollution. This approach should theoretically highlight land-use patterns, or at least pinpoint areas where serious measures should be taken. The Drastic method was developed in USA by the Natural Water Well Association (NWWA) in 1987. It is a standardized method for evaluating and mapping groundwater vulnerability, while taking into account most hydrogeological parameters, i.e. water depth, effective recharge, aquifer media, soil media, topography, impact of the vadose zone, and hydraulic conductivity. These factors are represented by weights and ratings which depend on their relative importance and local hydrogeological conditions. The weight-rate ratio is the Drastic index. The vulnerability index is mapped by overlapping the seven index maps. Manual mapping is long and tedious and seems unsuitable for this operation, but automatic mapping using software programs that process progressive changes in parameters also cannot accurately replicate the phenomenon because the vulnerability index is attributed to the area but not the outline. The pollution potential can be better represented by computational matrices whose elements represent the discretized field. This paper discusses its application to the alluvial aquifer of the El Madher plain, located around 15 km northeast of the town of Batna (northeastern Algeria). Zones susceptible to pollution were highlighted by mapping the vulnerability indices using Matlab matrices.