Abstract
Groundwater systems provide an important source of water supply as well as contributing baseflow to rivers, lakes and dependent ecosystems and so the impact of climate change on these systems needs to be understood. Calculating recharge to groundwater systems is, therefore, necessary to quantify what is typically one of the largest components of the groundwater balance. This study uses the national-scale recharge model developed for the British mainland and the 11 ensemble members from the Hadley Centre for rainfall and potential evaporation created by the Future Flows and Groundwater Levels (FFGWL) project to investigate the impact of future climate on groundwater resources. Changes to seasonal and monthly recharge for the 2050s and 2080s time slices have been produced for the whole modelled area and for river basin districts for England and Wales. Areal summaries and monthly time series of recharge values show a generally consistent trend of increased recharge in winter, decreased recharge in summer, and mixed pattern in autumn and spring. The work shows that increased winter rainfall is the main factor in increasing recharge. Water balance calculations reveal that over the 2050s and 2080s, the climate change “signal” predominates over the annual variability, which results in a clearer pattern of more recharge being concentrated in fewer months. This finding should prove useful for water resources planners to assess the resilience of groundwater resources to climate change. Further work is recommended to understand the sequencing of flooding and drought events and to the effects of soil health and land cover changes in the future analysis.
Highlights
Groundwater is a hidden asset that contributes significantly to maintaining the overall quality of our environment and is a globally important source of water (Taylor et al, 2012)
It is necessary to establish whether the future climate have upwards or downwards trends to enable the changes observed in the spatial distribution of recharge for the time slices (2050 s and 2080 s) to be confirmed
These results demonstrate how the recharge processes can “balance” the predicted modification of meteorological conditions associated with climate change, i.e. drier summers and wetter winters
Summary
Groundwater is a hidden asset that contributes significantly to maintaining the overall quality of our environment and is a globally important source of water (Taylor et al, 2012). In the UK, groundwater provides over 75 percent of water for drinking and industrial use, in southern England (Lerner and Harris, 2009). There is a need to understand the occurrence, extent and frequency of ground water (Clearwater) flooding (Hughes et al, 2011). All these processes occur in groundwater systems that are largely driven by rainfall recharge as their main input. Rainfall recharge (Lerner et al, 1990) is defined here as recharge occurring from rainfall directly from where it lands on the ground surface. In the UK, rainfall recharge occurs typically between October and March when actual evaporation is lower than rainfall (and the soil moisture deficit is zero). Recharge replenishes aquifers during the autumn, winter and early spring and storage allows groundwater abstraction to be undertaken all year round
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