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Ecology and Environment

Oughton, Deborah ; Skipperud, Lindis ; Bradshaw, Clare ; Barnett, Catherine ; Hinton, Thomas ; Fevrier, Laureline ; Salbu, Brit

European Commission

来源: NERC Open Research Archive

【 摘 要 】

Groundwater is a significant component of public water supply and water use in the UK as well as sustaining environmentally important flows to our rivers and wetlands. 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 m3day-1. Most of the groundwater is abstracted from the principal aquifers in southern, eastern and central England. The role of groundwater in the management of water resources is likely to become more important because it can be used to support public water supply and ecosystem services during more severe drought periods projected under climate change. However, the understanding of how groundwater will respond to changes in coupled climate and human stresses is limited and insufficient research has been undertaken. Groundwater recharge generally refers to the downward vertical flux of water at the water table. Potential recharge refers to drainage from the base of the soil, which depends on the rainfall, runoff, interflow and evaporation balance of the soil, as well as soil and vegetation characteristics. Most potential recharge occurs during the winter months when soils are wet and potential evaporation rates are lower. Ten separate studies have been reported which project potential recharge rates in the UK over the 21st century. These studies cover 12 sites and predominantly focus on the Chalk aquifer in south-east England, although other studies have investigated the Permo-Triassic sandstone in the Midlands and the Devonian and Carboniferous limestone in Scotland. Overall, there is some consensus about changes in mean annual potential recharge in the UK. Most studies simulate a decrease by the 2050s but projections are in the range ~ -30 �C+21%. There is most agreement for Chalk catchments in southern England, where the length of the recharge season is likely to shorten. There is less agreement about the impact of climate change on recharge to the Chalk aquifer in East Anglia. There is some agreement over future changes in recharge to Permo-Triassic sandstone aquifers, although the small number of studies means that there is limited evidence to support the findings. Overall it seems that recharge rates will decrease by the 2080s over most aquifers. However, there is significant uncertainty about the magnitude of changes due to a cascade of uncertainty from and about greenhouse gas emissions scenarios, climate model uncertainty, and the effect of socio-economic change on land-use planning and water demand. Knowledge of potential future changes in groundwater levels is important, not only because they are indicative of the total amount of water stored in an aquifer, but also because they affect the degree to which an aquifer can be exploited. Potential changes in the spatial and temporal distribution of groundwater levels in the future will also affect groundwater flood risk. Whilst there is some agreement as to how groundwater levels will change in the future, an insufficient number of studies have been undertaken. There are significant differences in current projections, again due to multiple sources of uncertainty. There is a clear need to undertake more research, particularly at the national scale, which adopt consistent approaches, explore the full range of uncertainties and are spatially coherent.