Groundwater in Fractured Bedrock Environments: Managing Catchment and Subsurface Resources
Fractured bedrock aquifers have traditionally been regarded as low-productivity aquifers, with only limited relevance to regional groundwater resources. It is now being increasingly recognised that these complex bedrock aquifers can play an important role in catchment management and subsurface energy systems. At shallow to intermediate depth, fractured bedrock aquifers help to sustain surface water baseflows and groundwater dependent ecosystems, provide local groundwater supplies and impact on contaminant transfers on a catchment scale. At greater depths, understanding the properties and groundwater flow regimes of these complex aquifers can be crucial for the successful installation of subsurface energy and storage systems, such as deep geothermal or Aquifer Thermal Energy Storage systems and natural gas or CO2 storage facilities as well as the exploration of natural resources such as conventional/unconventional oil and gas. In many scenarios, a robust understanding of fractured bedrock aquifers is required to assess the nature and extent of connectivity between such engineered subsurface systems at depth and overlying receptors in the shallow subsurface.
Catchment-scale heterogeneity of flow and storage properties in a weathered/fractured hard rock aquifer from resistivity and magnetic resonance surveys: implications for groundwater flow paths and the distribution of residence times
-
Published:January 01, 2019
-
CiteCitation
J.-C. Comte, U. Ofterdinger, A. Legchenko, J. Caulfield, R. Cassidy, J. A. Mézquita González, 2019. "Catchment-scale heterogeneity of flow and storage properties in a weathered/fractured hard rock aquifer from resistivity and magnetic resonance surveys: implications for groundwater flow paths and the distribution of residence times", Groundwater in Fractured Bedrock Environments: Managing Catchment and Subsurface Resources, U. Ofterdinger, A.M. MacDonald, J.-C. Comte, M.E. Young
Download citation file:
- Share
Abstract
Groundwater pathways and residence times are controlled by aquifer flow and storage properties, which, in weathered/fractured hard rock aquifers, are characterized by high spatial heterogeneity. Building on earlier work in a metamorphic aquifer in NW Ireland, new clay mineralogy and analyses of geophysical data provided high spatial resolution constraints on the variations in aquifer properties. Groundwater storage values derived from magnetic resonance sounding and electrical resistivity tomography were found to largely vary laterally and with depth, by orders of magnitude. The subsequent implementation of hillslope, two-dimensional numerical groundwater models showed that incorporating heterogeneity from geophysical data in model parametrization led to the best fit to observations compared with a reference model based on borehole data alone. Model simulations further revealed that (1) strong spatial heterogeneity produces deeper, longer groundwater flow paths and higher age mixing, in agreement with the mixed sub-modern/modern ages (mostly <50 years) provided by independent tritium data, and (2) areas with extensive weathering/fracturing are correlated with seepage zones of older groundwater resulting from changes in the flow directions and are likely to act as drainage structures for younger groundwater on a catchment or regional scale. Implications for groundwater resilience to climate extremes and surface pollution are discussed together with recommendations for further research.
- age
- aquifers
- boreholes
- clay minerals
- climate
- climate change
- data integration
- Donegal Ireland
- drainage
- drainage basins
- Europe
- fluid flow
- fractured materials
- fracturing
- geophysical methods
- geophysical surveys
- ground water
- hydraulic conductivity
- hydrogen
- hydrogeology
- instruments
- Ireland
- isotopes
- methods
- mineral composition
- mixing
- models
- movement
- numerical models
- pollutants
- pollution
- properties
- radioactive isotopes
- recharge
- regolith
- residence time
- resistivity
- resonance
- seepage
- sheet silicates
- silicates
- simulation
- spatial variations
- storage
- surveys
- temporal distribution
- tomography
- tritium
- water content
- water management
- water storage
- weathered materials
- weathering
- Western Europe
- Gortinlieve Catchment