Dual-flow in karst aquifers toward a steady discharge spring (Presciano, Central Italy): influences on a subsurface groundwater dependent ecosystem and on changes related to post-earthquake hydrodynamics

Abstract

The Presciano spring system (Central Italy) is fed by a fractured carbonate regional aquifer and shows peculiar hydrogeological, physicochemical, hydrogeochemical and biological features that led to hypothesis about local superimposition of a dual groundwater flow system. The components of this system are fast-flow and baseflow groundwater paths. Hydrogeochemical and isotopic (δ18O and δD for H2O, and δ34(Formula presented.) and δ18(Formula presented.)) data were used to test this conceptual model. Differences in physico-chemistry and ion concentrations were recorded for two main spring sectors, attributable to different groundwater flowpaths. Environmental isotope analyses allowed distinguishing different recharge areas for the two groups: more depleted values (-10.4 ‰ δ18O and -71 ‰ δD) indicated the existence of a flowpath influenced by a higher elevation recharge area, whereas enriched isotope signals (-9.9 ‰ δ18O and -66 ‰ δD) supported a regional recharge area of local water infiltration. The existence of a dual flow system is also reflected in the relationship between SO4 2- concentration and SO4 2- isotope data. The isotopic pattern of SO4 2- reflects the seasonal contributions by the two flow paths to the springs: after snowmelt, the isotopic sulphate value in the spring outlet is very similar to the spring sector fed by the fast flow component, while, after the spring exhaustion period, its isotopic composition is very similar to the base flow spring sectors fed by the fracture network. The influence of the different flowpaths has also been highlighted by changes in water isotope composition after the 2009 L'Aquila earthquake in this area: the strong homogeneous response of the spring system can be attributed to a cleaning of the fracture system, which affected the aquifer at regional scale. Additional investigations adopting the geoelectrical tomography technique highlighted the possibility of the existence of a buried karst channel or at least high-permeability shear zone at the contact between the carbonate aquifer and the fluvio-lacustrine quaternary deposits, where the spring system is located. Biological indicators, such as groundwater copepods also showed a response to the dual flowpath regime. The results of this study have great relevance for a better management of the Presciano spring habitat, which is increasingly threatened by anthropogenic disturbance. © 2014 Springer-Verlag Berlin Heidelberg

Earthquake-Related Changes in Species Spatial Niche Overlaps in Spring Communities

“…Copepods also comprise ~80% of the total meiofauna density at TS 14, 22, 23 . In particular, we tested if the earthquake-induced higher discharge increased the niche overlap of copepod species by reshaping their micro-distribution in the TS.…”

Exploring the distribution of groundwater Crustacea (Copepoda and Ostracoda) to disentangle aquifer type features—A case study in the upper Tajo basin (Central Spain)

“…Groundwater invertebrates are good hydrological biomarkers for groundwater flow paths in the saturated zone (Eisendle‐Flöckner & Hilberg, ; Mori, Kanduč, Opalički‐Slabe, & Brancelj, ; Mösslacher, ; Petitta, Caschetto, Galassi, & Aravena, ) and the epikarst layers (Meleg, Moldovan, Iepure, Fiers, & Brad, ; Pipan & Culver, ), changes in groundwater pathways feeding spring systems (Galassi et al, ; Stoch, Artheau, Brancelj, Galassi, & Malard, ) and to discriminate between the phreatic and unsaturated zones of aquifers (Galassi, Huys, & Reid, ; Sket & Bole, ). These services provided by the groundwater biota result from the particularities of species distributions, typically being unevenly and mostly narrowly dispersed owing to species‐specific habitat preferences and low dispersal abilities (Brancelj, ; Galassi et al, ; Sket, ).…”

Exploring copepod distribution patterns at three nested spatial scales in a spring system: habitat partitioning and potential for hydrological bioindication

“…The values of δ 18 O recorded at Santa Liberata indicated a lower elevation recharge area, corresponding to the main recharge area of the Gran Sasso aquifer (Petitta et al, 2015). Moreover, the elevation derived by the isotope signal is very similar to those recorded in springs located northwards (San Calisto and Tirino River Valley springs: Tallini et al, 2014), fed exclusively by the Gran Sasso aquifer.…”

“…Similarly, beyond their uniqueness in terms of degree of endemism, rarity and relictuality De Laurentiis, 1997a, 1997b;Botosaneanu, 1998;Barquín and Scarsbrook, 2008;Galassi et al, 1999Galassi et al, , 2011Cantonati et al, 2011), some groundwater species have been claimed as good candidates for identifying dual aquifer flowpaths (Petitta et al, 2015;Mori et al, 2015) or changes in groundwater pathways feeding spring systems (Stoch et al, 2009;Galassi et al, 2014). However, the reliability of spring meiofauna assemblages as hydrological biotracers has not been investigated to any great extent.…”