Changes in groundwater levels, temperature and quality in the UK over the 20th century: an assessment of evidence of impacts from climate change

Bloomfield, John P. ORCID:; Jackson, Christopher R.; Stuart, Marianne E.. 2013 Changes in groundwater levels, temperature and quality in the UK over the 20th century: an assessment of evidence of impacts from climate change., LWEC, 14pp.

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Groundwater is a significant component of public water supply and water use in the UK, as well as sustaining environmentally important flows in rivers and wetlands. Groundwater is vital to the economy of the UK and has been valued at about £8 billion. Across England and Wales the average annual recharge to the main aquifers is ~7 billion m3. About 30% of this is abstracted from aquifers at a rate of ~7 million m3/day, mostly from principal aquifers in southern, eastern and central England. Groundwater temperature varies with depth and is a function of the background geothermal gradient and ambient temperature at the land surface. The average temperature of groundwater in the upper parts of aquifers is around 10-11º C. The natural, or baseline, quality of groundwater is highly variable and reflects the chemistry of the recharge water and the geochemistry of the soils and rocks through which it moves and is stored. The quality of groundwater has been extensively impacted by a wide variety of pollutants throughout the 20th century with nitrate being the most widespread. There is a consensus that relatively little is known about how groundwater has responded to climate change. Groundwater systems are naturally very variable in their characteristics and are expected to respond to climate change in a complex way. In addition, groundwater systems are sensitive to other environmental factors, such as land use change. Consequently, distinguishing between the impacts of what may be relatively small climate change signals from other environmental changes is very challenging. In the UK, groundwater levels are highly variable and long-term trends may be influenced by a wide range of factors, such as: changes in recharge caused by changes in land-use and agriculture practices; changes in land cover, particularly urbanisation, and changes in groundwater abstraction with time. At groundwater level monitoring points that have been selected to avoid these external influences, there is no evidence of a change in groundwater levels as a result of changing climate. Groundwater level records in the UK are typically less than 20 years long. Consequently, even if climate induced trends in groundwater levels are present the measurement record at the vast majority of monitoring points may be too short to enable climate trends to be seen. In addition, groundwater level data are generally of not good enough quality to enable more subtle changes, such as changes in the timing and length of the recharge season, to be investigated and characterised. This is because the monitoring was not originally designed to monitor for the effects of climate change. There is some evidence for a rise in average groundwater temperatures. For the period 1990 to 2008 it has been estimated that there may have been an increase in average temperature of groundwater of between 0.01C/yr and 0.02C/yr. There have been no systematic investigations of the relationship between groundwater quality and climate change in the UK. However, long-term changes in baseline groundwater quality have been documented as being due to other environmental and societal changes not related to climate change. For example nitrate in groundwater has increased by an average of 0.34mgNO3/l/yr during the second half of the 20th century, a rise entirely consistent with increases in agricultural application of fertilizer. The effects of these other environmental changes are thought to be far more significant in terms of their impacts on groundwater quality than any direct effects from climate change. The current monitoring of groundwater level, temperature and quality is inadequate for the investigation and quantification of climate change impacts and it is recommended that dedicated monitoring of groundwater is established to enable assessment of future climate change impacts on groundwater.

Item Type: Publication - Report
Funders/Sponsors: LWEC
Additional Information. Not used in RCUK Gateway to Research.: Report available for free download from URL above
Additional Keywords: GroundwaterBGS, groundwater, climate change
NORA Subject Terms: Earth Sciences
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Date made live: 19 Sep 2013 11:04 +0 (UTC)

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