Groundwater quality assessment using water quality indices and GIS technique with kriging interpolation in Maadher plain of Hodna, northern Algeria

Abstract

In a semi-arid region of Maadher, central Hodna (Algeria), groundwater is the main source for agricultural and domestic purposes. The quality of groundwater is strongly influenced by surrounding anthropogenic activities under the effect of climate change. The objective of this study was to assess the quality of groundwater and its suitability for use in irrigation and drinking using quality indices and to identify polluted wells using geographic information system (GIS) by the spatial interpolation method of Kriging. The results showed that all water samples contained high levels of calcium, chlorine and sulfate, as well as alarming concentrations of nitrate ions that exceed WHO standards. Piper's diagram indicated that the groundwater hydrochemical facies is a sulfate-chloride-nitrate-calcium combination (SO₄2−-Cl−-NO₃⁻- Ca2+ water type). According to the water quality indices, the classifications of WQIs are similar, the majority of samples are in the poor water category and just over 10% of all samples are in the very poor water category, and less than 10% of the samples represent the good to excellent quality category. Irrigation water indices indicate that all samples are acceptable. Water quality maps generated using ordinary Kriging method show that high concentrations of salinization parameters (Ca2+, Na+, Mg2+, SO₄2− and Cl−) were found north of the Maadher zone and decrease as we move south; except for bicarbonate and nitrate which were high in the center of the zone, near the Wadi Bousaada depression. The study revealed that groundwater quality has been affected by anthropogenic activities represented by excessive agricultural practices and inflows from Wadi Bousaada. The groundwater saturation index was calculated to know the origin of the mineralization and the chemical processes that occur in the aquifer.