Investigating aquifer vulnerability employing DRASTIC model and GIS techniques in Menzel Habib Shallow Aquifer, South-Eastern Tunisia

Groundwater vulnerability assessment shows an extreme sensitivity to in situ anthropogenic pollutants. A dichotomous assessment of geological and hydrological (inter alia) characteristics makes it possible to determine the vulnerability of an aquifer system. The natural vulnerability of an aquifer can be severely compromised by human activities. The physical structure and material composition of aquifers shows resistance to contaminants transport from surface to groundwater. Currently, numerous methods have been posited evaluating aquifer's vulnerability. Similarly, the DRASTIC and DRASTIC pesticides models utilize computer algorithms and hydro-geological data within a Geographical Information System (GIS) to compute spatial aquifer vulnerability. The DRASTIC and DRASTIC pesticides models are constructed using combined spatial datasets on Depth to groundwater (D), Aquifer Recharge (R), Aquifer media (A), Soil media (S), Topography (T), Impact of the Vadose Zone (I) and Hydraulic Conductivity (C) of the aquifer. The degree of vulnerability of the aquifer system can be evaluated by computing sensitivity analysis of DRASTIC index using GIS, showing the contribution of each parameter to vulnerability sensitivity. The GIS was used to develop a vulnerability map for Menzel Habib aquifer area. The obtained results indicated that moderately vulnerable areas are of 5%, while areas of no risk correspond to 95% using DRASTIC index. Otherwise, DRASTIC pesticide index indicated that 15% area of low vulnerability, 84% moderately vulnerable and 1% high vulnerability. The central area of Menzel Habib aquifer showed a low vulnerability due to dense human settlement and a deeper water level. However, agricultural areas recorded high vulnerability risk. Menzel Habib's environmental and socio-economic development is dependent on policy makers and planner's ability to use information effectively for decision making. The obtained groundwater vulnerability maps provide a basis for this aimed at protecting the aquifer from pollutants. Additionally, land use and development activities can be informed by mapping variables, showing that agriculture areas are highly vulnerable as compare to settlement areas

Water quality indexes on aquifer systems from a semi-arid region – a new vulnerability index to sustainable groundwater management

Groundwater is an important resource applied for multiple purposes and needs to be protected all over the world. Tunisia is facing the problem of water scarcity due to its arid and semi-arid climate. This region has a rather unstable climate with irregular rainfall quantity and spatial distribution leading to either periods of drought or intensive rainy periods. Groundwater salinization is a major problem associated to natural and anthropogenic processes. The inland aquifer from Menzel Habib (southeastern Tunisia) is exploited for domestic purposes and agricultural activities. Groundwater from Menzel Habib aquifer shows a significant total dissolved solids content (TDS: 1.60-8.71 g/L), associated to the high sodium, chloride, sulfate, magnesium, and calcium water concentrations, and could be used as a water quality indicator. The integration of water contamination indicators and groundwater vulnerability models is a new vision and first-hand information on groundwater quality assessment and sustainable management. The main aim of this study is to assess the vulnerability of the Menzel Habib aquifer using GIS-based vulnerability models to provide information on groundwater contamination and to develop a new index for mapping groundwater vulnerability to salinization. The obtained results indicate different vulnerability degrees, varying from very extremely low to high vulnerability. The highest vulnerability areas are located on the western region, which could be associated to a lower deep of groundwater combined with evaporation processes, and a consequent salinity increase. A modified vulnerability index is proposed by adding to hydrogeological data an eighth parameter, corresponding to TDS water contents. The modified index is based on the standard DRASTIC index and the adding of TDS - DRASTIC_Sal. This new index is a simple approach for aquifer salinization vulnerability assessment, particularly on inland aquifers from arid and semi-arid regions with associated agricultural activities. The expected outcomes of the current study will be a helpful knowledge concerning the status of groundwater vulnerability from Menzel Habib region and will be a decision-making tool to be considered by authorities in land use planning as well as in groundwater resource management