Suitability assessment of shallow and deep groundwaters for drinking and irrigation use in the El Khairat aquifer (Enfidha, Tunisian Sahel) |
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| Authors: | Mouna Ketata Moncef Gueddari and Rachida Bouhlila |
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| Institution: | (1) Laboratory of Geochemistry and Environmental Geology, Department of Geology, Faculty of Mathematical, Physical and Natural Sciences of Tunis, University Campus, 1060 Tunis, Tunisia;(2) Modelling in Hydraulic and Environment Laboratory, National Engineers School of Tunis, Le Belv?d?re, BP 37, 1002 Tunis, Tunisia |
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| Abstract: | The El Khairat aquifer is an important groundwater aquiferous system, which is considered a major source for drinking and
irrigation water in Enfidha in Tunisian Sahel. The analysis of groundwater chemical characteristics provides much important
information useful in water resources management. Assessing the water quality status for special use is the main objective
of any water monitoring studies. An attempt has been made for the first time in this region to appreciate the quality and/or
the suitability of shallow and deep groundwater for drinking and irrigation. In order to attend this objective, a total of
35 representative water samples were collected during February 2007 from both boreholes (17) and wells (18); and analyzed
for the major cations (sodium, calcium, magnesium and potassium) and anions (chloride, sulphate, bicarbonate, and nitrate)
along with various physical and chemical parameters (temperature, pH, total dissolved salts, and electrical conductivity).
Based on the physico-chemical analyses, irrigation quality parameters like sodium absorption ratio (SAR), residual sodium
carbonate (RSC), percentage of sodium (Na%), and permeability index (PI) were calculated. In addition to this, iso-concentration
maps were constructed using the geographic information system to delineate spatial variation of qualitative parameters of
groundwater samples. The correlation of the analytical data has been attempted by plotting different graphical representations
such as Piper, Wilcox, and US Salinity Laboratory for the classification of water. The suitability of the water from the groundwater
sources for drinking and irrigation purposes was evaluated by comparing the values of different water quality parameters with
World Health Organization guideline values for drinking water. A preliminary hydrochemical characterization shows that most
of the groundwater samples fall in the field of calcium–magnesium–chloride–sulphate type of water. Majority of the samples
are not suitable for drinking purposes and far from drinking water standards. The high EC value and the percentage of Na in
most of the groundwater render it unsuitable for irrigation. Wilcox classification suggested that around 50% of both deep
and shallow groundwater samples are unsuitable for irrigation. According to the US Salinity Classification, most of the groundwater
is unsuitable for irrigation unless special measures are adopted. |
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