Abstract
Karst aquifer recharge areas are usually difficult to identify because of the complexity of these aquifers’ characteristics. On the other hand, their identification is very important in the aim of protecting the groundwater resources that these aquifers host. Regarding this topic, this paper presents an approach aimed at identifying karst aquifer recharge areas by the application of oxygen-18 and deuterium isotopes composition of groundwater coupled with hydrological features. Oxygen-18 and deuterium isotope composition of Capodacqua di Spigno Spring, in the South of the Latium Region, has been applied with rainfall and discharge values related to the feeding aquifer of this spring. As δ18O and δ2H values of groundwater samples are natural tracers of the recharge area’s elevation, we propose a model, based on the distribution of the basin surfaces involved as recharge areas, in relation to elevations. The model estimates, for any discharge value, the percentage of the topographic area involved in the aquifer recharge. The setting up of this simulated distribution is supported by a Weibull cumulative probability function. The results show that the measured discharges increase as larger areas with lower elevations are involved in the recharge process.
Highlights
Well-developed karst aquifers, characterized by slow infiltration through the rock matrix and fast flow through conduits and fractures, represent highly productive groundwater systems with a high degree of heterogeneity and anisotropy
The application of spring water isotopic concentration makes it possible to define the average elevation of recharge areas
This correlation should take into account the isotopic values variation of the rainfall input, a model, which is based only on isotopic values detected at the spring, was introduced
Summary
Well-developed karst aquifers, characterized by slow infiltration through the rock matrix and fast flow through conduits and fractures, represent highly productive groundwater systems with a high degree of heterogeneity and anisotropy. Identifying recharge areas coupled with karst aquifer hydrogeological characteristics, which are related to the main kind of groundwater drainage, is important information for sustainable management of these groundwater resources. Natural environmental stable isotopes together with other geochemical parameters are useful tools in cases where artificial tracing is not feasible such as at the scale of a regional aquifer system [3]. They have been applied to trace water flows inside the hydrological cycle from infiltration, influenced by chemical and isotopic precipitation characteristics, to discharge, due to water–rock interactions and geochemical processes [4,5].
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