Andrea Romanazzi(2), Francesco Gentile(1), Giuliana Trisorio Liuzzi(1), Maurizio Polemio(2), 2013, The sustainability of groundwater exploitation for agriculture in the case of a wide coastal karstic aquifer, 1st CIGR Inter-Regional Conference on Land and Water Challenges, pp. 76–76, Bari, 10-14 Sept. 2013,
URL: http://www.cnr.it/prodotto/i/272187

This note aims to define the sustainability of groundwater exploitation for agriculture in the case of a wide coastal karstic aquifer. Numerical modelling was used as a tool to point out the criteria to reduce the quantitative and qualitative groundwater degradation risks. The real heterogeneous aquifer has been simulated as an equivalent homogeneous porous media within cells or elements. Its surface extension is 2230 km2 and it was uniformly discretized into 97,200 cells, each one with an area of 0.6 km2. Vertically, to allow a good lithological and hydrogeological discretization, the area was divided into 12 layers, from 214 to -350 m asl. Inactive cells were used along the boundary with the confining Murgia-Salento aquifer, as conceptual underground watershed due to the absence of flow. A CHD (Constant Head Boundary) was used along the sea boundary, while additional boundary conditions were used for salinity modelling. The results of calibration can be summarised considering the correlation coefficient, equal to 0.92, the standard deviation, equal to 0.7, the mean square error, equal to 0.65 and the absolute mean residue (RMS), equal to 12%. The water budget of the study area was calculated in each cell using a GIS elaboration. Rainfall and temperature monthly data coming from 16 gauges were considered since 1915 until 2000, considering an infiltration coefficient (IC) for each hydrogeological complex. The period since 1925 until 1975 was selected to assess the water balance for the steady state conditions, thus avoiding the trend effect of climate change, particularly relevant in the area starting from the eighties. After implementing and calibrating the steady-state scenario two transient validate-scenarios were implemented for two decades_ eighties and nineties. In these decades the discharge increase for drinking and irrigation purposes and the recharge decrease due to climate variations were considered. The salinity and piezometric trends were thus obtained. As most of the global climate change models predict decreasing precipitation and increasing temperatures and hence evapotraspiration in the Mediterranean region, three forecasts piezometric scenarios, 2000-2020, 2020-2040 and 2020-2060 were subsequently implemented. On this basis, the quantity degradation of groundwater resources was assessed, showing a non-sustainability of the current trend of groundwater exploitation.

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