Vulnerability Mapping of an Apulian Deep Carbonate Aquifer Using GIS

Abstract

Computer techniques such as Geographic Information Systems are applied to the evaluation of the vulnerability of a deep carbonate aquifer. The study area, of about 150 km2, is located in the low Murgia Plateau (Apulia) and characterized by Mesozoic limestone and dolomite rocks of several thousand meters thickness. A wide and thick aquifer resides in these carbonate rocks. Its groundwater flows toward the sea mainly under pressure and with maximum piezometric level of about 200 m a.s.l.. Due to their high quality, the water resources of this aquifer are particularly valuable for the local communities and therefore must be protected from pollution and inappropriate use. The vulnerability map of the aquifer is an indispensable tool for the effective management of groundwater resources and to support environmental planning. Several approaches have been proposed by different authors to evaluate intrinsic vulnerability. Most of the methods for detailed vulnerability mapping are based on the integrated analysis of several variables using different algorithms. Geographic Information Systems are advanced computer tools for the analysis of georeferenced data in 2D and 3D and can be effectively applied to the implementation of evaluation models. In this study the SINTACS evaluation method was implemented in a GIS and a digital vulnerability map produced. The different data taken into consideration in this analysis, such as depth to water, actual infiltration, pollution attenuation capacity of unsaturated zone, land cover, hydrogeological features of saturated aquifer, hydraulic conductivity, terrain slope, geology and geological structures, were georeferenced and converted into digital form. Each variable corresponds to a separate data layer made of graphic and attribute data. The computerized multilayer analysis performed by the GIS is time effective and leads to more comprehensive and accurate results with better spatial resolution.