No abstract

Alpine areas, with normally fissured bedrock outcrops, do not typically contain important hydrologic reservoirs, except for small aquifers located in Quaternary sediments. By contrast, mountainous areas affected by deep-seated gravitational slope deformations (DSGSD), especially if covered by glacial sediments, contain large aquifers and are consequently promising for water exploitation. This last geological setting is observed, for example, in the lower Dora Baltea Valley (near the confluence with the Renanchio Basin) in which the Montellina Spring is located and exhibits a very high discharge. A multidisciplinary approach (detailed geological survey of the bedrock and Quaternary cover, as well as hydrogeological research based on tracer tests, hydrochemical analyses, and water balance studies) was used, allowing for a reconstruction of the geological and hydrogeological setting of the investigated area, also considering its environmental implications. The consequent hydrogeological model derives from the coexistence of some factors. In detail, the thick glacial cover, widespread in the intermediate sector of the slope, represents an important aquifer with a slow groundwater flow to the spring. The buried glacial valley floor, hosting this cover, can convey the groundwater from the high Renanchio Basin zone towards the low sector. The loosened bedrock of the low sector, consequent to DSGSD phenomena, favors the concentration of groundwater along the contact with the underlying normal fissured bedrock outcropping at the base of the slope. Finally, the flow until the spring essentially takes place through N100° trend open fractures and trenches. Part of the Montellina Spring discharge is also fed by the low Renanchio Stream, as highlighted by fluorescein tests, essentially using NE-SW oriented open fractures on the bedrock. The results of the investigation on the Montellina Spring can provide some insight regarding the hydrological potential of other alpine areas with a similar geological setting.

Thermal perturbation produced in the subsurface by open-loop groundwater heat pump systems (GWHPs) must be predicted and constantly controlled, especially in the shallow aquifers of more densely urbanized areas, in order to guarantee plants’ long-term sustainable use and to avoid adverse effects on adjacent geothermal systems. Transient conditions in the flow dynamic can be successfully modelled by means of numerical modelling tools. However, for small plants in suitable hydrogeological systems, an alternative tool for predicting the thermally affected zone (TAZ) around the injection well can be found in analytical solutions for steady advective transport in a shallow aquifer. The validity of using steady analytical solutions to predict the TAZ development at the end of two different cooling seasons (2010 and 2016) was tested in the Politecnico di Torino GWHP system (NW Italy). When fixing the constant thermal difference (ΔT) between the injection and abstraction wells at 5°C, results revealed that a rather reliable assessment of the TAZ of Politecnico di Torino GWHPs, in Turin shallow aquifer, can be performed by plotting the cumulative distribution function of the injected discharge rate (Q) and setting 63% as a steady value.

No abstract

As continuous groundwater monitoring in the upper sector of Rodoretto Valley (Germanasca Valley, Italian Western Alps) is hampered by logistical problem of data collection during winter and spring months, the only tools currently available to derive hydrogeological information are non-continuous and non-long-term dataset of spring discharge (Q), temperature (T) and electrical conductivity (EC). In order to quantity aquifer groundwater reserve, available Q dataset of a small mountain spring (Spring 1 CB) was investigated by applying the analytical solutions developed by Boussinesq (