The ICGC generates basic information about the nature and structure of the subsoil in 3D to contribute to the future challenges that climate change scenarios set out in terms of water supply and decarbonization. 

Within the framework of the work to assess the available groundwater resources in Catalonia, the ICGC has developed the 3D Model of Port del Comte aquifers on which the KARSYS method has been applied to delimit and quantify the volume of reservoirs associated with karstic aquifer discharge springs. 

The KARSYS method (a pragmatic approach to karst hydrogeological system conceptualisation) is a practical approach to know the location and extension of potentially available reservoirs in this area and their delimitation in qualitative terms. This approach was developed by Malard et al. (2012) and Jeannin et al. (2013) from the Swiss Institute for Speleology and Karstology (SISKA), and has been applied in the past by Turk et al. (2013) in aquifers of the Kanin Massif in the Julian Alps in Slovenia; or Ballesteros et al. (2015), in the high mountain aquifers in an area of the western and central of Los Picos de Europa Massif (N, Spain); and recently by Herms (2022) in the Port del Comte Massif (between the counties of Alt Urgell and El Solsonès). 

The application of the KARSYS method from a 3D model allows to approximate the extension and theoretical volumes associated to the groundwater reservoirs linked to the karstic springs that discharge the system. This method is a very valuable tool with potential diverse uses, such as guiding the location of possible future exploitations (wells) in strategic high mountain karstic aquifers. This would reduce the costs of new drilling for groundwater extraction, as well as the risks that these involve in this type of environment.

Imatge

This cartography is under the Creative Commons Attribution 4.0 International license.  More information

The aquifer system of the Port del Comte Massif

The Port del Comte corresponds to a thrust sheet within the mantle of Cadí. Cartographically, it has a triangular shape and is limited, to the East, by the Cardener fault; to the West, it is overlain by units from the Upper mantles; and to the South, it limits with the materials of the Ebro Foreland basin. The internal structure of the Port del Comte unit is formed by a series of folds in a general NE-SW direction. This structure is truncated by the Port del Comte fault that divides the unit into two sectors. 

The sedimentary series of the unit is characterized by a great thickness of Lower Eocene (from Ilerdian to Lower Lutetian) materials, overlying a Mesozoic basement formed by the Triassic, Jurassic (Alinyà area), Upper Cretaceous and Paleocene (Garumnian facies).

Imatge

Aquifer system of the Port del Comte Massif. a) Conceptual model of the hydrogeological functioning of the Port del Comte massif where the water divides and main flow lines are interpreted as well as the extension of the groundwater reservoirs associated with the different karst springs of the aquifer (Herms, 2022). b) Volumes of the groundwater reservoirs obtained from the updated 3D model (v1.0, December 2024).

From a hydrogeological point of view, Port del Comte is considered as an independent unit formed by a multi-aquifer system, where the fissured and karstified limestones of the Lower Eocene constitute the main aquifer level. Recharge occurs essentially in a diffuse manner throughout its outcrop and in a concentrated manner through the karst elements, from rain and snowmelt. Discharge occurs essentially in a natural regime through four main karstic sources, in addition to a diffuse drainage in the Northern sector: the Fonts del Cardener, the Font de Sant Quintí and the Font de Can Sala, the Font Aiguaneix and the diffuse drainage towards the Riu de la Vansa through the Riu Fred and its associated karstic siphon of the Font d’Andana or Padrinàs, and the rest of the tributaries.

Methodology: update of the 3D model and application of the KARSYS method

Based on the 3D model of geological surfaces obtained by Herms (2022) during 2024, a review and update was carried out to achieve greater adjustment and definition of the volumes of the groundwater reservoirs of the aquifer system of the Port del Comte Massif. 

Imatge

Reconstruction of the 3D aquifer model: a) structural and lithostratigraphic surfaces; b) volume of the lower Eocene karst aquifer.

The KARSYS method has been applied to the updated 3D model. This method is based on an explicit conceptual model for karstic aquifers that assumes that groundwater flow is predominantly conditioned by their geometry. By fixing the regional base hydraulic gradients, the method allows to delimit the volume of groundwater reservoirs associated to each of the karstic springs. 

Results and conclusions

• Considering the geometries obtained by applying the KARSYS method to the aquifer system of the Port del Comte Massif, it is concluded that the geological structure strongly conditions the reservoirs associated with the karstic springs, conditioning the dynamics of the system and the geochemical footprint of each of the springs (Herms, 2022). 
• The inferred groundwater reservoirs have a plan area between 0.67 km² (Can Sala reservoir) and 14.10 km² (les Fonts del Cardener reservoir) and a volume between 28.63 hm³ (Can Sala reservoir) and 3145.6 hm³ (les Fonts del Cardener reservoir). 
• It should be noted that these volumes do not correspond to the available water resources, so it would be necessary to know the secondary porosity of the system. These volumes also do not have a direct equivalence with the dynamic volumes of water in the reservoir that would have to be estimated using other method.  

For more information, you can consult the technical document explaining the development of the 3D model of aquifers in Port del Comte (TR- 0013/2024, Catalan).

Resources

Data visualization and format

• Viewer user guide (CAtalan)