Regional groundwater flow and interactions with deep fluids in western Apennine: the case of Narni‐Amelia chain (Central Italy)

Abstract

The elemental fluxes and heat flow associated with large aquifer systems can be significant both at local and at regional scales. In fact, large amounts of heat transported by regional groundwater flow can affect the subsurface thermal regime, and the amount of matter discharged towards the surface by large spring systems can be significant relative to the elemental fluxes of surface waters. The Narni‐Amelia regional aquifer system (Central Italy) discharges more than 13 m3 sec−1 of groundwater characterised by a slight thermal anomaly, high salinity and high pCO2. During circulation in the regional aquifer, groundwater reacts with the host rocks (dolostones, limestones and evaporites) and mixes with deep CO2‐rich fluids of mantle origin. These processes transfer large amounts of dissolved substances, in particular carbon dioxide, and a considerable amount of heat towards the surface. Because practically all the water circulating in the Narni‐Amelia system is discharged by few large springs (Stifone‐Montoro), the mass and energy balance of these springs can give a good estimation of the mass and heat transported from the entire system towards the surface. By means of a detailed mass and balance of the aquifer and considering the soil CO2 fluxes measured from the main gas emission of the region, we computed a total CO2 discharge of about 7.8 × 109 mol a−1 for the whole Narni‐Amelia system. Finally, considering the enthalpy difference between infiltrating water and water discharged by the springs, we computed an advective heat transfer related to groundwater flow of 410 ± 50 MW.

The Viterbo Hydrothermal System and Its Sustainable Exploitation, Central Italy

“…The thermal water flow is continuous from the north at an altitude of 320 m asl to the south at an altitude of 240 m asl with an horizontal hydraulic gradient of 0.008 [54] (Figure 4a and Figure 9), in accordance with the idea that the recharge area is located north of the Viterbo geothermal area, i.e. in the carbonate aquifer of the Umbria Marche Succession including the mountains of Narni -Amelia, the Martani Mountains, the mountains of north eastern Umbria, and the Sabini Mountains in central Apennines [20,25,55,56] (Figure 6). This hydrogeological structure covers an area of 742 km 2 , with an average annual precipitation of 1068 mm, an effective average annual infiltration of 637 mm (inputs), corresponding to 472.6 m 3 /y x 10 6 , and a total yield of springs of 15 m 3 /s corresponding to 473 m 3 /y x 10 6 (outputs) (Boni et al, Capelli et al) [34,57].…”

Assessing Indices Tracking Changes in River Geochemistry and Implications for Monitoring

“…The perturbation of K þ at 42 km in the flood period could be linked to the use of fertilizers or to the absence of uptakes by vegetation in winter when plants are dormant (Berner & Berner, 1996). Groundwater circulation dissolving gypsum, anhydrite and halite from Triassic evaporites of the Narni-Amelia aquifer system (Nera sub-basin) (Frondini et al, 2012) explain the considerable perturbation values of Cl À and Na þ .…”

Duvalo “Volcano” (North Macedonia): A Purely Tectonic‐Related CO2 Degassing System

“…In Italy many non-volcanic gas manifestations are present and most have been studied, both to define the origin of the emitted gases and to quantify their CO 2 output (e.g., Chiodini et al, 1999Chiodini et al, , 2011Chiodini et al, , 2020Frondini et al, 2008Frondini et al, , 2012Minissale et al, 1997;Rogie et al, 2000). Many of them have higher CO 2 outputs (e.g., Chiodini et al, 2011Chiodini et al, , 2020 with respect to Duvalo, sometimes up to more than one order of magnitude (e.g., Mefite D'Ansanto 2,000 t d −1 ; Chiodini et al, 2010).…”