Consulting
Understanding karst groundwater requires a 3D assessment of the geology. KARSYS is a deductive approach based on the geology of a site and the hydraulic principles governing karstification. Once a site is defined, SISKA deploys a 4 step approach: (i) identifying the karstic properties of the aquifers, (ii) establishing a 3D geological model of aquifer units, (iii) generating a 3D hydrogeological model through integration of hydrological data and (iv) identification and delimitation of flow systems.
This results in:
- the delimitation of spring basins;
- the volumetric assessment of groundwater resources;
- a model of underground water flow paths.
VisualKARSYS, is a free online service for building and viewing KARSYS models.
KarstMOD (hydrological and hydraulic models) makes it possible to simulate groundwater dynamics quantitatively, and assess recharge (effective infiltration), storage and flow at one or more outlets.
SISKA applies methods and tools to study the vulnerability of groundwater,the delimitation of protection zones and the search for sources of pollution.
In collaboration with other specialist partners, SISKA offers solutions for prospecting and exploiting groundwater. This includes the analysis of spring flows and simulating of flows under different scenarios (meteorological, anthropogenic impacts, exploitation strategies).
SISKA proposes specific approaches for assessing the hazards karst poses on construction and various activities.
Civil engineering and karst
During construction, particularly underground (tunnels, galleries, reservoirs...), the karstic environment can present structural problems. These include unexpected voids, pressurized water and the presence of poorly consolidated sediments. Using the Karst ALEA method, the SISKA can predict potential hazards, propose protective measures to minimise them and make recommendations to manage problems should they occur.
Wind turbines and karst
SISKA is developing methods for assessing and supporting the installation of wind turbines in karst regions. The aim is to minimise the risks of karst to infrastructure stability. An informational brochure on this issue has been published by the SSS.
Infiltrations
In an urban karstic environment, the federal recommendation to infiltrate grey water (roof and road water) is problematic because this infiltration may facilitate collapses. SISKA can draw up collapse hazard maps and assessments. In the event of a collapse, targeted recommendations can be issued.
If infiltration sites are selected, SISKA can issue recommendations on acceptable infiltration flow rates and conditions.
Collapse hazards
The karstic subsurface contains numerous cavities, sometimes covered by a thin layer of soil. Collapses are therefore not uncommon. SISKA can produce site specific collapse hazard maps and assessments.
Geothermal
The specific characteristics of karst can lead to poor constraints on geothermal projects. Indeed, due to the significant circulation of air and water, karstic massifs are colder than other environments. However, karstic springs drain geothermal heat and represent an interesting resource. SISKA has unique expertise that enables it to assess energy potential and develop a strategy for geothermal exploitation in carbonate regions.
SISKA can prepare prescription maps for the installation of geothermal probes based on groundwater vulnerability criteria.
The construction projects and various human activities (tunnels, galleries, roads, wind turbines, geothermal energy, infiltration of grey water, etc.) can have an impact on the karstic environment. SISKA is specialised in assessing and minimising these impacts in accordance with the Ordinance on Environmental Impact Assessment (OEIE).
SISKA has developed a series of tools and methods for such assessments (Visual KARSYS, Karst ALEA and others).
Impact on groundwater
In karstic environments, almost all rainwater infiltrates the subsoil and, after a few days to weeks, emerges from springs that then feed rivers. Developments and structures can modify the water's flow regime and quality. These changes can be critical for drinking water catchments, rivers and underground aquatic fauna. SISKA can assess these impacts and seek solutions that minimise them.
Impact on underground fauna
The underground environment is home to a specific and varied fauna including several endemic species. Underground habitats are very stable because they are relatively unaffected by external variations (climate, urbanisation, etc.). However, their inhabitants are very sensitive to change. SISKA can assess the fauna present, the sensitivity of the habitats and the potential or actual influences of a development or construction project.
Impact on the underground climate
The temperature and humidity (>98%) underground is almost constant year-round. Any disruption to these climatic conditions will have an impact on the cave, the fauna and any archaeological artefacts found there. Furthermore, the underground atmosphere is often enriched with CO2 and radon, which can cause problems if the cave is occupied for long periods (e.g. archaeological excavations, tourist visits). SISKA can measure and monitor the characteristics of an underground climate system and can therefore assess the impact of a development or construction project on cave climate.
Impact on the karstic landscape
Karstic landscapes have been recognized worldwide for their importance to our natural heritage (18 locations are listed as UNESCO World Heritage sites and numerous others are listed in the federal landscape inventory). In Switzerland, sinkholes, potholes and caves are often not explicitly inventoried, even though they form part of the country's natural heritage. SISKA can identify these objects, assess them and seek solutions to minimise potential impacts on these features.
The Karst ALEA method was developed specifically to assess the problems posed by karstic environments during the construction of a structure and the impact of the project on the environment. It can be used to predict the position and characteristics of karstic cavities in a limestone massif.
It also serves as a basis for drawing up collapse hazard maps.
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