Rethinking Water Management in Karst Aquifers: A Multi-Specialty Approach to Sustainability - Mike Buchanan 2025

Abstract

This paper examines the critical challenges posed by anthropogenic drawdown of karst aquifers, emphasising the ecological services these systems provide. It critiques the reliance on traditional hydrological models, particularly Darcy's Law and advocates for a paradigm shift towards sustainable water management practices that prioritise ecological integrity and community engagement. Additionally, it explores alternative hydrological models that are more suited to the unique characteristics of karst systems, providing a framework for improved water management.

Introduction

Karst aquifers are vital sources of freshwater, characterised by their unique geological karst features, formations, including caves, sinkholes, and underground rivers. These systems play a crucial role in supporting biodiversity and providing essential ecological services, such as water filtration, habitat provision, and carbon sequestration. However, the anthropogenic perception of surplus groundwater availability has led to over-extraction, resulting in significant ecological consequences. This paper aims to propose a multi-specialty approach that integrates hydrology, ecology, and community practices for sustainable water management in karst aquifers.

Anthropogenic Drawdown of Karst Aquifers

Moisture Depletion and Ecological Services

Groundwater extraction from karst aquifers leads to moisture depletion in epikarstic soils, adversely affecting vegetation and soil health. These soils are critical for supporting diverse ecosystems and their services, including nutrient cycling and habitat provision. The loss of moisture not only threatens plant life but also disrupts the delicate balance of the entire ecosystem.

Heat Plumes and Climate Change

The drawdown of groundwater can create reductions in soil moisture and evapotranspiration that can exacerbate heatwaves and reduce convective potential (Mu et al., 2021; Zeng et al., 2017; IPCC, 2021), leading to reduced rainfall and exacerbating desertification. As temperatures rise, local microclimates are altered, further impacting the ecological health of the region. This phenomenon highlights the interconnectedness of groundwater management and climate change, emphasising the need for sustainable practices.

Biodiversity Loss

Cave-dwelling bats and other species reliant on stable water levels are particularly vulnerable to the impacts of groundwater extraction. These bats play a vital role in pest control. Their decline can have cascading effects on ecosystem services. The disruption of natural stygobitic biodiversity further underscores the importance of protecting karst aquifers.

Limitations of Traditional Hydrological Models

Complex Flow Paths and Sensitivity

Karst aquifers exhibit highly variable flow paths influenced by fractures, conduits and voids. Traditional models often fail to capture this heterogeneity, resulting in mismanagement of water resources. Additionally, the sensitivity of karst ecosystems to changes in water levels and quality necessitates a more nuanced understanding of hydrological processes.

Proposed Solutions for Sustainable Water Management

Avoiding Groundwater Abstraction in Karst Systems - To protect karst aquifers, it is essential to focus on fluvial systems for water extraction. This approach alleviates pressure on karst aquifers and promotes the sustainable use of water resources. Tapping into resurgent points can provide a viable alternative, allowing for the extraction of groundwater without significantly disrupting the aquifer's overall health, if well managed.

Critique of Managed Aquifer Recharge (MAR) - While MAR is often promoted as a solution for replenishing aquifers, its application in karst environments may not be suitable. The complexity of karst hydrology can lead to inefficiencies and unintended consequences. Instead, a cautious approach that prioritises the protection of existing water sources and ecosystems is recommended.

Curriculum Improvements in Hydrology Education - A multi-specialty educational approach is needed to equip future hydrologists with the tools necessary to manage karst aquifers sustainably. This includes specialised courses on karst hydrology, ecology, and integrated water management, as well as practical training in field settings.

Alternative Hydrological Models for Karst Systems

Given these limitations, alternative modelling frameworks are required that can better represent the duality of diffuse and conduit flow in karst.

Discrete Fracture Network (DFN) Models

DFN models simulate flow through fractured media by representing fractures as discrete entities. This approach captures the heterogeneity of karst aquifers and provides insights into how fractures influence groundwater flow and transport, especially under low-flow, fracture-dominated conditions.

Dual-Continuum Models

These models treat the aquifer as having two distinct continua: one for the matrix (the rock) and one for the fractures. This allows for the simulation of flow and transport in both the porous matrix and the more permeable fractures, providing a better representation of the dual nature of flow in karst systems.

Karst Aquifer Models (KAM)

Specific models have been developed to address the unique features of karst aquifers, such as the Karst Aquifer Model (KAM). These models often incorporate elements of both surface and subsurface hydrology, tailored to the specific hydrological processes in karst environments. They can simulate the effects of recharge, discharge, and the influence of surface water on groundwater systems.

Hydrogeological Simulation Models (e.g., MODFLOW)

MODFLOW is a widely used groundwater modelling software that can be adapted for karst systems by incorporating specific parameters and boundary conditions that reflect karst characteristics. However, in low flow karst aquifers, MODFLOW’s reliance on porous media assumptions and regional-scale calibration leads to significant limitations. To improve its reliability, enhanced fracture representation should be incorporated, either through embedded DFN approaches or hybrid stochastic methods, and models must be calibrated with detailed field datasets.

Integrated Surface Water-Groundwater Models

These models consider the interactions between surface water and groundwater, which is particularly important in karst systems where surface features can significantly influence subsurface flow. They provide a holistic view of the hydrological cycle in karst areas and help in understanding the impacts of land use and climate change on both surface and groundwater resources.

Stochastic Models and Field Validation

Stochastic models incorporate randomness and uncertainty into the modelling process, which is particularly useful in karst systems where variability is high. These models allow for the assessment of risks and uncertainties in groundwater management, helping to predict the effects of different scenarios on water availability and quality. Importantly, no modelling framework alone can determine groundwater divides (Ghasemizadeh et al., 2012; Reimann et al., 2014) or flow pathways without validation from field evidence such as dye tracing, water chemistry, and tracer testing. This combined approach ensures ecological protection, particularly for karst biodiversity and stygofauna, which are often overlooked in UK regulatory practice despite obligations under the EU Habitats Directive(Soley et al., 2012).

Discussion

This reliance on model outputs also reflects a deeper systemic blind spot: the neglect of subterranean ecological services. Groundwater ecosystems host microbial and invertebrate communities, including stygofauna, that provide regulating and supporting functions such as nutrient cycling, water purification and resilience against contamination. Despite obligations under the EU Habitats and Groundwater Directives, these communities remain almost entirely absent from UK regulatory practice and water-resource assessments.

The treatment of Chalk aquifers in national groundwater studies (e.g. Soley et al., 2012) illustrates this institutional narrowing of perspective. By assuming that porous-media models are sufficient to represent aquifer function, such approaches risk reinforcing overconfidence in abstractions while diverting attention from ecological impacts. This is not simply a technical shortcoming, but a form of epistemic closure: privileging hydraulic predictability over ecological complexity. Addressing these deficiencies requires rethinking groundwater management in the UK as an integrated socio-ecological challenge. That means, embedding ecological monitoring alongside hydrological models, explicitly incorporating uncertainty in licensing decisions, and recognising groundwater ecosystems as service providers in their own right. Only through such systemic reform can statutory water management begin to reconcile human demands with the long-term health of karst and Chalk aquifers.

References

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