Groundwater suitability for drinking and agriculture purposes using irrigation water quality index and multivariate analysis: case of Sidi Bouzid aquifer, central Tunisia

The Sidi Bouzid region is one of the main centers of agricultural production in Tunisia, especially for vegetable crops (18% of national production), arboriculture (13% of almond production and 10% of olive oil), and milk production (125 million liters in 2012 around 12% of national production) [PREDD (Plan Regional d’Environnement et de Développement Durable du gouvernorat de Sidi Bouzid), 2014]. Therefore, the groundwater quality of Sidi Bouzid aquifer was studied to evaluate the quality of the hydrochemical parameters to determine its suitability for both agricultural and drinking purposes. Thirty groundwater samples were collected and analyzed. The obtained results showed that the groundwater contains high values of dissolved ions dominated by SO 4 , Mg and Ca. Gypsum, anhydrite and halite dissolution, as well as direct and reverse ion exchange are the main processes of chemical evolution in the Sidi Bouzid aquifer. Multivariate statistical techniques, such as PCA and HCA, helped to focus on the hidden yet important variables and understand their roles in affecting the groundwater quality. Compared to the World Health Organization (Guidelines for drinking water quality, 3rd edn, vol 1. Recommendations. WHO, Geneva, 2008) and National Water Exploitation and Distribution Company SO.N.E.D.E (NT.09.14) guidelines for drinking water, results showed that the concentrations of major and trace elements were within the admissible concentration rate. Chemical indices such as the percentage of sodium (Na%), sodium adsorption ratio (SAR), Kelly’s ratio, and permeability index (PI) showed that more than 70% of the analyzed samples can be used for irrigation. The irrigation water quality index (IWQI) classes vary from severe (SR) to moderate restriction (MR). The visualization of the IWQI distributions, using GIS software, shows that the moderate restriction class (MR) is the dominant class.