Using GIS and Geostatistical Techniques for Mapping Piezometry and Groundwater Quality of the Albian Aquifer of the M’zab Region, Algerian Sahara

Abstract

The M’zab region is subject to an arid Saharan climate where surface and sub-surface waters are of little importance. The Albian Aquifer, commonly called Continental Intercalary (CI), main component of North Western Sahara Aquifer System (NWSAS/SASS), constitutes the most extensive aquifer formation of the region. In our study area, the CI is identified, as a regional subset, as the Albian Aquifer of M’zab Region (AAMR). Its groundwater resources are considered the only source available to meet the growing needs of drinking water supply, agriculture and industry. This aquifer is heavily exploited by a very large number of wells (more than 750). Its supply is very low, so it is a very low renewable layer. This requires periodic monitoring and control of its piezometric level and its physico- chemical quality. The objective of our study is to know the current state of this aquifer, while studying the variation of its piezometry for the period 2010-2018, and also the chemical quality of its groundwater by analyzing more than 90 samples over the entire study area. The application of geostatistics by kriging and the steps of analysis, modelling and calculation of semivariogram have enabled us to draw up maps of the various hydrogeological and hydrochemical parameters. As a result, twelve thematic maps were gridded using Geostatistical tools of ArcGIS software. The water-level-change map showed a significant drop in the groundwater level over the entire M’zab region and especially around the major cities (Ghardaïa, Berriane, Metlili and Zelfana) with more than 8 meters. Chemical analyses of the Albian groundwater in the study area show the dominance of evaporite facies (Cl--Na+-Ca2+) with low concentrations than the Algerian Standards for Drinking (ASD). All the water quality indices (WQI) that have been mapped reveal that the groundwater samples were suitable for drinking and irrigation with a high quality of water located in the south of the study area.