Determining recharge distribution in fractured carbonate aquifers in central Italy using environmental isotopes: snowpack cover as an indicator for future availability of groundwater resources

Abstract

Environmental isotopes were used to determine the source and to understand the physical–chemical processes involved in groundwater movement along a flowpath. This study applies groundwater stable isotopes to assess snow-cover influence on the recharge processes of some regional carbonate aquifers of central Italy. Starting with extensively investigated aquifers, 17 springs were selected and sampled (June–October 2016) for isotope analyses. The δ18O–δD results follow the local meteoric water line; the low mismatch between the 2016 sampling surveys suggests that those springs are not influenced by seasonal variability. Nevertheless, the average elevations of recharge areas calculated using the vertical isotope gradient were higher compared to those obtained with hypsographic profiles. This means that the relevant contribution to recharge comes from higher elevation areas; hence, snowpack coverage and snowpack persistence over time on recharge areas were analysed using satellite images. Four different relationships between the snowpack characteristics and the elevation of recharge areas have been identified. These offer relevant information about the different degrees of dependence of the regional aquifers of central Italy on the recharge due to high-elevation subbasins where the snowpack cover is significant. A possible correlation emerges between computed isotope recharge elevation and mean snow cover elevation, revealing how snowmelt is a primary source for aquifer recharge. Consequently, to evaluate the risk of groundwater resource depletion in a climate-change scenario, there is discussion on how a potential snow-cover reduction would affect the recharge rate of mountainous aquifers.

Groundwater recharge distribution due to snow cover in shortage conditions (2019–22) on the Gran Sasso carbonate aquifer (Central Italy)

“…Laboratory in Milan (Italy) using a mass spectrometer Finnigan Delta Plusmass equilibrated at 25 °C as described by Epstein and Mayeda (1953) for oxygen. The analytical precision is about ± 0.1‰ for δ 18 O and ± 1‰ for δ 2 H (Petitta et al 2022).…”

“…The δ 18 O and δ 2 H stable isotopes have been largely used to determine groundwater recharge areas, with their elevations, and water flow paths (González-Trinidad et al 2017;Sappa et al 2018;Wachniew 2015;Arellano et al 2020;Vespasiano et al 2015). Applying the use of stable isotopes for calculating the mean recharge elevation is still a basic tool, with particular reference to mountainous aquifers where recharge areas are distributed in a wide elevation range (Petitta et al 2022). The mean elevation of the recharge area calculated by isotope values of spring water is also representative (Jasechko et al 2017;Jódar et al 2021).…”

Refining the origin of thermal water using stable isotope, hydrochemistry and GIS approaches in Jiaoxi, Taiwan

“…This characteristic renders it valuable for estimating the source elevation of single‐point groundwater or springs. Apart from the review by Jasechko (2019), recent studies continue to widely apply isotopic methods to determine recharge elevation in regions, such as Africa (Balagizi et al, 2022; Hamad et al, 2018), China (Wu et al, 2021), Haiti (Gourcy et al, 2022) and Italy (Fronzi et al, 2021; Petitta et al, 2022). However, the isotopic approach alone primarily aids in identifying the recharge elevation rather than the recharge area.…”

Hydrodynamic characterization of carbonate aquifers by atypical pumping tests without interruption of drinking water exploitation

“…The case study is about the Gran Sasso aquifer one of the most important in Central Italy [5] which has been studied for engineering purposes and for springs' characterization; from a hydrodynamic point of view, the available data are referred only to discharge, chemical and isotopic features [9][10]. The lack of hydrodynamic data and the presence of well elds have allowed the execution of atypical step-drawdown test using the exploited wells, both for pumping and head monitoring.…”