Reliability of the VESPA Index in Identifying Spring Vulnerability Level

To assess spring vulnerability level, the vulnerability estimator for spring protection areas (VESPA) index has been proposed. The VESPA index method is based on the joint use of discharge, electrical conductivity, and temperature data, measured at the spring location. In this paper the VESPA index method has been examined through the analysis of observed time series with respect to the following aspects: (1) the time extension of the data set, (2) the use of averaged data, and (3) the number of missing data. For this purpose four springs fed by different geological systems were considered. The outcomes of the statistical analysis show that the VESPA index is a reliable way to identify higher vulnerability levels while some uncertainty occurs in the identification of low and medium vulnerability levels.