Impacts of climate and land use change on groundwater quality in England : a scoping study

Ascott, M.; Lewis, M.; Gooddy, D.; Mackay, J.; Smedley, P.L.; Cartwright, C.. 2022 Impacts of climate and land use change on groundwater quality in England : a scoping study. Nottingham, UK, British Geological Survey, 134pp. (OR/22/076) (Unpublished)

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Abstract/Summary

In 2019, the Environment Agency (EA) carried out a risk assessment following the government Climate Change Committee's methodology. This work highlighted groundwater quality as one area where the quality of the EA’s plan was weak, and progress in managing the risk was poor. In the same year, the UK parliament declared a climate emergency, and the COP26 summit in 2021 has brought climate change and the need to adapt into even stronger focus. This prompted the need for further evidence gathering and in 2021 the EA commissioned BGS to undertake a scoping study to explore the impacts of climate and land use change on groundwater quality. The study had the following objectives: (1) To determine what key risks to groundwater quality may be associated with climate change, (2) what adaptation and mitigation measures may be needed, (3) how EA groundwater quality monitoring may need to change in the future associated with climate change and (4) what are the research and evidence gaps associated with the impacts of climate and land use change on groundwater quality. The study addressed the aims above through a number of desk-based activities which are detailed in this report. A review of the findings of UKCP18 has illustrated the potential changes to the climate of England over the 21st century as context for changes in groundwater resources and quality. Air temperature, evapotranspiration and sea level are all predicted to increase throughout the 21st century. Whilst the direction of change in annual precipitation is unclear, wetter winters and drier summers are predicted, with greater magnitude extreme winter rainfall events. No published work has evaluated the impact of climate change based on UKCP18 data on groundwater recharge and levels. A review of previous studies using UKCP09 and other climate projections has shown limited consistency in the direction of change in long term average groundwater recharge and levels in England. There is some consistency in changes to seasonality in groundwater recharge and levels, with increased recharge and levels in winter, decreased recharge and levels in summer. There is limited evidence for changes in extremes (increasing high winter groundwater levels). A review of international literature related to climate change and groundwater quality has shown an overall worsening of groundwater quality over the next 50 – 80 years, although the trajectory of change for individual parameters is highly uncertain. Some parameters have a high level of confidence in a relationship with climate variables (e.g. shallow groundwater temperature and air temperature, sea level rise and salinity in coastal aquifers). However, for many components of climate change and water quality parameters, our understanding of relationships is near non-existent and speculative. A workshop was held on “Groundwater Quality into the Future” as part of this study. The purpose of the workshop was to gather input from both Environment Agency and external stakeholders regarding the key issues related to future groundwater quality, and the priorities for adaptation, management and research. This workshop identified uncertainty in impacts of climate change on groundwater quality, the need for holistic approaches to management of groundwater in the terrestrial water cycle, and the need for continued monitoring as cross cutting themes. A number of focus areas were also identified: nutrients, emerging substances, changing rainfall characteristics, changing temperature, groundwater rebound, urban development and construction, changing salinity and groundwater ecosystems. The potential impacts of climate change on groundwater quality are illustrated through five case studies – Brighton, Chichester, Birmingham, Eden and Dove. The case study areas cover a range of different hydrogeological (Chalk, Permo-Triassic sandstone and Carboniferous Limestone), geographical (north, south, inland, coastal) and land use settings (rural, urban). For each case study we discuss the hydrogeological conceptualisation and water quality issues of concern. We then present the results of UKCP18 (temperature, rainfall) and the derived products eFLaG (rainfall, evapotranspiration, groundwater recharge, groundwater levels) and GeoCoast (sea level rise), before providing a qualitative evaluation of the impacts of climate change on groundwater quality. Across all five case study areas, air temperatures are predicted to increase by up to 3°C. This could increase reaction rates for degradation of contaminants, but such increases may only be marginal. Increased sea levels are predicted to increase salinity in coastal aquifers. The direction of changes in long term average rainfall and recharge is uncertain, but the magnitude of changes is predicted to be small. There is generally a high confidence of increased rainfall and recharge seasonality and greater magnitude of extreme events in winter. This has the potential to result in spikes of pollutants, but this could also be offset by increased dilution. Land use change, and in the case of Birmingham, groundwater level recovery from historic over-abstraction, may have a greater impact on groundwater quality than changes in climate. On the basis of the literature review, case studies and input from stakeholders, an initial prioritisation of the potential risks to groundwater quality associated with climate change has been made. The relatively small increases in temperatures and changes in long term average rainfall and recharge make these a low priority. The local nature of increases in sea level affecting coastal aquifers make these a medium priority. The high confidence in changes in rainfall and recharge seasonality and extremes and impact through changes to leaching, spikes and dilution make these a relatively high priority. The highest priority risk is land use change, whether induced by climate change or otherwise. Land use change may change contaminant sources and pathways, and is both highly uncertain and has a potentially high impact on both groundwater and other components of the terrestrial water cycle. Building on the previous project tasks, a number of recommendations have been made regarding evidence gaps, monitoring approaches, regulation and adaptation measures. Specific recommendations are detailed in the table below and general recommendations are discussed herein. Further research is required to address the significant evidence gap related to how drivers of groundwater quality are likely to change in the future, and what the hydrogeological system response to changes in multiple, competing drivers may be. This is a large area of work and should be prioritised based on stakeholder needs. Subsequent work is required to consider the impacts of future changes in groundwater quality on downstream receptors, and what management strategies should be adopted. Recommendations for changes in groundwater quality monitoring detailed below are speculative at this stage given the high level of uncertainty associated with the impacts of climate change on groundwater quality. A key recommendation from the workshop was for better integration of groundwater resources and quality in regulation, as well as better integration of groundwater as a whole within the terrestrial water cycle and urban planning. Given the uncertainty regarding the impacts of climate and land use change on groundwater quality, “no regrets” adaptation measures are most appropriate at this time. These measures, detailed below will address groundwater quality needs under current climate and land use and in any future. However, as “no regrets” measures address current groundwater quality issues, future issues which are not currently a concern (e.g. the next generation of emerging contaminants) will not be impacted by these approaches. This highlights the importance of addressing the evidence gaps above through targeted research projects. Detailed project proposals to address these gaps are beyond the scope of this report and should be co-produced between the Environment Agency, BGS and other stakeholders.

Item Type:	Publication - Report
Funders/Sponsors:	British Geological Survey, Environment Agency
Additional Information. Not used in RCUK Gateway to Research.:	This item has been internally reviewed, but not externally peer-reviewed.
Additional Keywords:	GroundwaterBGS, Groundwater
Date made live:	21 Nov 2022 11:14 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/533586

Item Type:

Publication - Report

Funders/Sponsors:

British Geological Survey, Environment Agency

Additional Information. Not used in RCUK Gateway to Research.:

This item has been internally reviewed, but not externally peer-reviewed.

Additional Keywords:

GroundwaterBGS, Groundwater

Date made live:

21 Nov 2022 11:14 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/533586