Groundwater flow dynamics and distribution of hydrochemical facies using GIS in Hodna Plain, M'Sila, Southeastern Algeria

Abstract

With the aid of the Geographic Information System (GIS), the present study aims to describe the relationship between groundwater flow systems and the distribution of chemical facies. The research also discusses the different geochemical processes which are responsible for the evolution of groundwater chemistry. Analytical studies of 25 groundwater samples indicate mean cation values such as Ca2+ (209.1 mg∙l1-), Mg2+ (116 mg∙l1-), Na+ (239 mg∙l1-) and K+ (2.8 mg∙l1-). The mean anion values are SO42- (3.7 mg∙l1-), Cl- (22.5 mg∙l1-), and NO3- (2.2 mg∙l1-). The GIS using topo to raster and multivariate statistical techniques were applied to the groundwater quality analyses obtained in order to define the major control factors that affect the plain hydrochemistry of Hodna. The statistical analysis reveals the presence of three groups, presenting an increased potential of salt content in the groundwater flow direction. Initially, in the aquifer boundaries and in the infiltration areas, the facies result as bicarbonate. In the southern part of the plain, groundwater becomes SO4-Cl rich, because of the dissolution of salt formations and the presence of the Hodna salt water lake. The Cluster Analysis has described the effects of rock water activity and overexploitation of water intended for irrigation as being responsible for altering groundwater chemistry in the area. Rock-water interaction diagrams show chemical weathering caused by precipitation, along with dissolution of minerals forming soil. The scattered plots among ions revealed geochemical processes such as carbonate weathering, silicate weathering, cation exchange and reduction of sulphate.