The Geoethical Case Against Reservoirs in Karstified Carbonate Terrains: Interdisciplinary Evidence and Policy Guidance – Mike Buchanan 2025

Abstract 

Karstified carbonate terrains present unique hydrogeological, geomechanical, geochemical, and ecological vulnerabilities that render surface and subsurface reservoirs high-risk infrastructure. This paper synthesises multidisciplinary evidence demonstrating why avoidance should be the default policy, clarifies circumstances where rigorous, exceptional mitigation might be considered and proposes operational, monitoring, legal frameworks to protect subterranean ecosystems and downstream stakeholders.

Introduction Karst systems

Characterised by dissolution conduits, caves, sinkholes, and heterogeneous porosity - exhibit rapid, anisotropic flow and high uncertainty in subsurface geometry (Ford & Williams, 2007). Traditional engineering approaches that assume continuous confining layers or predictable transmissivity are ill-suited to karst systems, creating substantial geoethical obligations to prioritise avoidance over modification (Palmer, 1991; Smart & Hobbs, 2015).

Hydrogeological Risks

Karst conduits enable fast, preferential flow that circumvents natural attenuation and engineered barriers, increasing transport velocity of contaminants and stored fluids (Gunn, 2004). The spatial discontinuity and stochastic distribution of voids compromise site characterisation and modelling - standard drill-and-test programs commonly miss critical features (Mitchell, 2003). Pressure perturbations from storage operations (filling, pumping, injection) can induce new pathways or enlarge existing conduits, altering regional flow regimes unpredictably (Worthington et al., 2000).

Geomechanical and Structural Risks

Carbonate dissolution and episodic collapse generate subsidence and sinkhole hazards that threaten embankments, liners, and other reservoir structures. Loading and changing pore pressures can trigger collapse in pre-weakened zones; tectonic stresses and gravitational torque further modulate mechanical stability over decadal timescales (Kefalas et al., 2016; Waltham et al., 2005). Geomechanical models must therefore incorporate coupling between chemical dissolution, stress redistribution, and long-term creep - complexities often beyond routine design practice.

Hydrochemical and Biogeochemical Risks

Introduced storage waters or altered redox/chemistry mobilize sorbed contaminants and adjust saturation states, accelerating dissolution or precipitation and changing permeability (White, 1988). Even “benign” waters can disrupt endemic groundwater microbiomes, shifting nutrient cycles and attenuative capacity. These biogeochemical changes may mobilise metals and degrade water quality over long time frames (Bourke et al., 2018).

Ecological and Biodiversity Considerations

Subterranean ecosystems host specialised stygofauna and microbial communities that provide critical ecosystem services (nitrification, denitrification, biodegradation). Such communities are extremely sensitive to chemical and physical perturbations; impacts may be irreversible on human timescales (Halsall & Humphreys, 2010). Ethical stewardship demands their inclusion as primary receptors in risk assessments, not secondary considerations.

Monitoring, Detection, and Remediation Challenges

Early detection of leaks or ecological shifts is difficult: conduit networks produce low signal-to-noise responses and standard monitoring wells may not intersect key flow paths. Tracer tests can help but are spatially and temporally limited; remediation in karst conduits is technically challenging, costly and often ineffective at restoring baseline conditions (Chen & Goldscheider, 2014).

Socio-legal and Economic Implications

High uncertainty increases liability, regulatory hurdles and community opposition. The long-term stewardship obligations and potential for transboundary impacts necessitate conservative permitting and robust financial assurances (Gunn & Linder, 2016). Cost–benefit analyses often under-account for ecological loss and indefinite monitoring liabilities.

When, if Ever, Consider Karst Sites? 

Karst systems should be considered for reservoir construction only under stringent, exceptional conditions:

  • Demonstrable absence of active karstic connectivity within the footprint via multi-year, multidisciplinary investigations (dense borehole arrays, 3D geophysics, speleological surveys, repeated tracer tests).
  • Geomechanical analyses showing mechanical stability under expected loads and tectonic regimes.
  • Hydrogeochemical compatibility proven by controlled test injections and long-term monitoring demonstrating negligible alteration to resident groundwater chemistry and biology.
  • Ecological baseline characterisation (metagenomics, stygofauna surveys, eDNA studies) and bioassays confirming tolerance to proposed storage water.
  • Legally enforceable operational limits, triggers tied to ecological indicators, and financial assurances for remediation and long-term stewardship.

Operational Recommendations and Best Practices

  • Default to avoidance; prioritise off-stream, above-ground, fully lined storage outside adjunct recharge zones.
  • If unavoidable, use conservative engineering: redundant containment (double-liners, cutoffs), load-minimising embankment designs and grouting only after rigorous proof of efficacy.
  • Implement comprehensive, long-term monitoring: continuous pressure/chemistry sensors, distributed tracer networks, ecological indicators, and periodic 3D geophysical surveys.
  • Permit conditions must require adaptive management, immediate cessation triggers, and long-term financial surety for ecological remediation.
  • Mandate interdisciplinary oversight teams (karstologists, hydrogeologists, geochemists, ecologists, geotechnical engineers, ethicists) throughout project life.

Geoethical Imperatives

Modifying karst systems for storage imposes intergenerational risks and potential irreversible losses. Geoethical principles require prioritising protection of subterranean ecosystems, full disclosure to stakeholders and conservative decision-making frameworks that favour non-intervention when uncertainty is high (Croft & Barker, 2017).

Conclusion

Karstified carbonate terrains present persistent, multi-faceted risks, hydraulic, mechanical, chemical, biological and legal, that make reservoirs and adjacent, adjunct storage inappropriate default choices. Avoidance should be the guiding policy; exceptions demand exceptional, multidisciplinary proof of safety, stringent operational controls and long-term stewardship commitments. Elevating karstology to a primary discipline in site assessment and decision-making is essential to uphold geoethical responsibilities and protect subterranean resources.

References

  • Bourke, S. et al. (2018) ‘Biogeochemical impacts of introduced waters in karst aquifers’, Journal of Hydrology, 556, pp. 123–136.
  • Chen, Z. and Goldscheider, N. (2014) ‘Remediation challenges in karst aquifers’, Hydrogeology Journal, 22(3), pp. 597–607.
  • Ford, D. and Williams, P. (2007) Karst Hydrogeology and Geomorphology. John Wiley & Sons.
  • Gunn, J. (2004) Encyclopedia of Caves and Karst Science. Routledge.
  • Gunn, J. and Linder, P. (2016) ‘Policy and legal frameworks for karst protection’, Environmental Policy Review, 12(2), pp. 45–60.
  • Halsall, G. and Humphreys, W. (2010) ‘Stygofauna vulnerability and conservation’, Aquatic Conservation, 20(4), pp. 501–512.
  • Kefalas, G. et al. (2016) ‘Geomechanics of sinkhole formation under loaded conditions’, Engineering Geology, 204, pp. 56–68.
  • Mitchell, P. (2003) ‘Limitations of standard site characterization in karst’, Quarterly Journal of Engineering Geology, 36(1), pp. 23–29.
  • Palmer, A. (1991) Origin and Morphology of Limestone Caves. Clarendon Press.
  • Smart, P. and Hobbs, P. (2015) ‘Karst hydrogeology: uncertainty and management’, Water Resources Management, 29(7), pp. 2153–2167.
  • Waltham, T., Bell, F. and Culshaw, M. (2005) Sinkholes and Subsidence: Karst and Cavernous Rocks in Engineering and Construction. Springer.
  • White, W. (1988) Geomorphology and Hydrology of Karst Terrains. Oxford University Press.
  • Worthington, S.R.H. et al. (2000) ‘Hydraulic behavior of karst aquifers: implications for engineering’, Hydrogeology Journal, 8(1), pp. 16–33.
  • Croft, J. and Barker, R. (2017) ‘Geoethics and groundwater: principles for decision-making’, Ethics in Science and Environmental Practice, 4(1), pp. 12–29.

 

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