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GIS-based DRASTIC, Pesticide DRASTIC and the Susceptibility Index (SI): comparative study for evaluation of pollution potential in the Nabeul-Hammamet shallow aquifer, Tunisia
Makram Anane & Bessem Abidi & Fethi Lachaal &
Atef Limam & Salah Jellali
Abstract Three vulnerability index models were applied to assess the pollution potential of Nabeul-Hammamet shallow aquifer, Tunisia: DRASTIC, Pesticide DRASTIC and the Susceptibility Index (SI). An output map layer of each one was obtained using a geographic information system (GIS). The SI layer was overlain with DRASTIC and Pesticide DRASTIC and the percentage areas of agreement and divergence in vulnerability categories were extracted. DRASTIC results suggest the aquifer has mostly low vulnerability. Pesticide DRASTIC and SI identify three vulnerability categories (low, moderate, high) in the aquifer. Published data on current chemical groundwater composition indicate that parts of the aquifer are highly contaminated, revealing that DRASTIC underestimates the risk of pollution; Pesticide DRASTIC and SI reect this risk better. Agreement in vulnerability categories between the two last models is found for 64% of the aquifer area. To help manage land-use allocation and prevent Nabeul-Hammamet-aquifer contamination, DRASTIC is not recommended. Pesticide DRASTIC and SI are recommended but for slightly different applications. SI helps in the monitoring of current vulnerable areas and, thus, in contamination prevention. Pesticide DRASTIC could better intervene as a criterion in a multi-criteria analysis to select the best sites for specic on-the-ground practice or future land use.
Keywords DRASTIC . SI . Vulnerability mapping . Groundwater protection . Tunisia
Introduction
The available water resources in Tunisia are about 4,860 million m3/year, of which 32 % comes from shallow groundwater (World Bank 2009). Citizens have long depended on this groundwater for domestic, agricultural and industrial purposes and currently most parts of rural areas are entirely served by groundwater. Growing population along with the associated industrial and agricultural expansions are stressing the aquifers through the need for increasing withdrawals and the risk of contamination from chemical inltration, dumping of pollutants and agricultural inputs (van Beynena et al. 2012). The potentially polluting nature of substances produced and used by man has increased dramatically in recent decades (heavy metals, nitrate, hydrocarbons, pesticides, pathogens, etc.; Henri 1975) along with their disposal into vulnerable ecosystems from point and non-point pollution sources (municipal and industrial...