A regional spring database for groundwater management: The preliminary results of a case study in Molise region (south Italy) and the future perspectives

A clear understanding of the groundwater system plays a leading role in the effective management of water resources and sustainable development. There is, therefore, a need to consider all available datasets, collate other supplementary data and update the present hydrogeological databases as an important source of information for decision-makers. Springs could be considered as hydraulic features for characterizing the basin-scale groundwater flow when there are not wells in a study area or there is limited access to them. In this study, the springs in some river basins in Molise region (southern Italy) are investigated. Between 1 and 1556 m a.s.l. (622 m a.s.l. on average), a total of 2681 springs (1620 perennial and 1061 non-perennial springs) were identified based on the Istituto Geografico Militare topographic maps at a 1:25000 scale. In springs, the hydraulic head is almost equal to the elevation head (h≈z). Regarding that groundwater flows from high to low hydraulic head (h), it could be concluded that the groundwater body generally flows from the mountainous area in the south and southwest towards the coast of Adriatic Sea in the north and northeast.

For further investigation, 1237 springs in Fortore and Saccione river basins were considered and the following factors (as indicators of the areas with a high probability of groundwater spring presence) were obtained from the digital elevation model for spring orifices: altitude, slope degree, slope aspect, curvature, plan curvature, profile curvature, topographic wetness index (TWI), stream transport index (STI) and stream power index (SPI). Following log-transformation of altitude, slope degree, slope aspect, SPI, STI and TWI for obtaining more symmetric statistical distribution, the springs were categorized into three groups through the Grouping Analysis in ArcMap 10.8: Group 1 with 101 springs; Group 2 with 1003 springs; and Group 3 with 132 springs. The springs in Group 2, Group 3 and Group 1 occur at high (639 m), medium (475 m) and low (150 m) altitudes, respectively. The slope of spring orifices in Group 2 and Group 3 is almost similar, but steeper than that of Group 1. The SPI and STI increase from Group 1 to Group 3 while the TWI and slope aspect are not significantly different between the spring groups. The R-squared values show that altitude and slope are the most important variables for discriminating the groups. A literature study shows a greater probability of spring groundwater occurrence in areas at a higher altitude and with a steeper slope, but this should be confirmed in our study area after applying some modeling techniques and considering more complex relationships.

This study presents a general overview of groundwater hydrogeology in some river basins in Molise region. It is noteworthy that the project is still ongoing and the database will be updated with a wider range of variables (e.g., hydrogeological complexes, distance to tectonic elements, spring discharge and spring water temperature when available) to obtain a comprehensive spring database and empower researchers supporting decision-makers for groundwater management.