New geological maps of Berwick-upon-Tweed to help future-proof natural water supply

Over 95 per cent of the water supply for the Tweed catchment, home to Berwick-upon-Tweed, is provided by groundwater. The Fell Sandstone Formation is the principal aquifer supplying drinking water, as well as being a vital resource for farming and industry in the region. Careful management of this critical resource is particularly important in a changing climate.

Climate projections indicate that, by 2050, the north-east of England may see summer and winter rainfall at 31 per cent lower and 25 per cent higher than current averages, respectively. Drier summers and wetter winters will affect the water balance in the aquifer, so understanding and accounting for the anticipated changes are critical in ensuring sustainable abstraction.

Nearly a century on from the last geological survey of the Berwick-upon-Tweed area, the Environment Agent (EA) commissioned BGS to review the geological map of the area to inform a new groundwater flow model of the Fell Sandstone Formation. This work was needed to improve understanding of the regional groundwater system, strengthen the evidence base for water security and support key decisions in the abstraction licensing strategy.

Ultimately, the mapping of the aquifer will help the EA, water abstractors and the local community to ensure sustainable abstraction and reduce risks from contamination to protect the water quality. This informed management will help to ensure the water supplies for Berwick-upon-Tweed are resilient to climate change.

We have commissioned the British Geological Survey to undertake this new survey of the Fell Sandstone Formation and surrounding strata to help us undertake our regulatory role in protecting groundwater underlying Berwick and the surrounding area.

The updated mapping will improve our understanding of the regional groundwater system and any implications on the future availability of water and climate change impacts. This will help in considering applications for new abstraction licences or renewals and/or increases of existing abstraction licences, where we require good quality and up-to-date information on the water environment.

Diane Steele, senior north-east area groundwater technical specialist, EA.

The new geological mapping and groundwater modelling have revealed that the local aquifer system is more complex than previously thought, with compartmentalisation of the groundwater system within the Fell Sandstone Formation aquifer as well as connectivity between the aquifer and water-bearing sandstone bodies in the adjacent rock formations. This work is informing a programme of borehole drilling by the EA to further develop our understanding of the interactions between water-bearing sandstones in Fell Sandstone Formation and underlying strata, and the implications for future water supply.

The new geological maps are being used as inputs for groundwater modelling, which is a key tool to better understand the controls on groundwater flow within the aquifer. Developing our understanding of the connectivity within the aquifer system is critical for assessing the effects of abstractions and evaluating the potential impacts of both changes in usage and changes in climate, helping to ensure the groundwater resource can support the region well into the future.

Tim Kearsey, head of BGS Integrated Geology.

The geological map data produced from this work will form part of the national geological map and will be freely accessible via the Onshore GeoIndex in its next update. More information on the mapping of Berwick-upon-Tweed can be found on BGS’s Story Maps.