Development of a GIS Based Procedure (BIGBANG 1.0) for Evaluating Groundwater Balances at National Scale and Comparison with Groundwater Resources Evaluation at Local Scale

The ISPRA (Italian National Institute for Environmental Protection and Research) has developed a GIS based procedure (BIGBANG 1.0—“Nationwide GIS-based hydrological water budget on a regular grid”) for evaluating all the factors of the monthly groundwater balance at National scale, using Python programming language. The procedure is based on spatial environmental information at very high resolution, often available on the WEB, in formats easily usable by the main geographic information systems. The hydrological factors of total precipitation, actual evapotranspiration, surface runoff and aquifer recharge are evaluated for a grid of 1 km resolution. The tool has been applied to the Campania Region (southern Italy) for the period 1996–2015, also defining for all factors the LTAA (Long Term Annual Average). These results and the monthly evaluations have been compared with groundwater balances carried out at local scale, in a carbonate groundwater body. The comparison shows that the lithological and hydrogeological features, much more detailed at local scale, can influence some factors of the balance, but the final amount of the recharge is comparable. Finally, this comparison, apart the above cited observations, represents a valid test for the BIGBANG 1.0 procedure and for its future implementation in the next versions.