SPI and recession curves analysis for karst spring management. A case study in central Italy

Water crises have become more and more frequent in recent years. In fact, the ongoing climate changes have led very often to periods of drought, which, together with the increasing of groundwater exploitation, leads to a depletion of thess resources, which are fundamental for human life. Most of the most important springs, in the world, are located in karst areas. Specifically, for a large part of the Mediterranean region, karst springs play an essential role in water supply systems. The quantitative analysis of karst aquifers is therefore of primary importance, in order to undertake a sustainable management of groundwater resources. Monitoring the karst spring discharge during the entire hydrological year is recommended. When measurements are not possible, spring discharge estimation, should be done. In this study, authors monitored the Capodacqua di Spigno Spring from January 2018 to September 2020. They have measured the surplus discharges in the river near the spring, using a current-meter. It was thus possible to reconstruct the flow rate delivered by the spring for the entire monitoring period. The most important value to be considered, in groundwater management, is the minimum discharge that the spring supplies during the year. In this paper, an existing forecasting method, that uses the Standard Precipitation Index (SPI), for the estimation of the minimum annual spring discharge, in the Capodacqua di Spigno Spring, was applied. The forecasting method using the SPI does not give any indication on the timing of the minimum flow rate. Using the recession curves, it was possible to estimate when the expected minimum will occur. The estimated minimum flow rates were compared with the measurements carried out and with the real flow rates supplied by the spring. In conclusion, it has been demonstrated how important is to associate discharge estimation methods with its monitoring. The comparative analysis in fact leads to a better knowledge of the spring drought phenomenon.