The importance of monitoring for the determination of aquifer vulnerability and spring protection areas

Spring water resources are an irreplaceable source of drinking water supply and therefore must be adequately protected in terms of quality and quantity. The assessment of an aquifer’s vulnerability to pollution is the key stage for the sizing of protection areas. The information regarding the type of aquifer and its behavior is rather poor and, with the exception of data related to geological surveys, few hydrogeological data are available (aquifer tests, geological surveys, etc….). A suitable method to analyze the behavior of an aquifer is to monitor the three parameters of spring water: flow rate, temperature and electric conductivity. The temporal variations of these parameters, especially during major infiltrative events, allow us to acquire basic data to assess the aquifer’s vulnerability. This paper describes the hydrogeological situation and the monitoring data of 12 springs fed by different types of aquifers (karstic, fractured and porous), equipped with automatic data loggers that measure flow rate, temperature and electric conductivity. For each spring the vulnerability of the aquifer was evaluated through a detailed hydrogeological study (monitoring data, site surveys, chemical analysis of water, tracer tests). Next, using the monitoring data the vulnerability index to pollution was calculated using the half-life time and the VESPA methods. The overall results of the study have been compared in order to highlight the main issues raised by the different methods used.