Hydrogeological conceptual model of the Spittal area - Project Groundwater Northumbria

This report has been produced by the British Geological Survey (BGS) on behalf of Project Groundwater Northumbria, the Flood and Coastal Innovation Programme (FCIP) project managed by Gateshead Council. It uses existing data and information to provide a conceptual understanding of the hydrogeology of the Spittal area, whilst discussing recent groundwater trends and groundwater flood susceptibility in the area. It also provides information on how historic coal mining may have impacted the groundwater system. The report shows two schematic cross-sectional diagrams to visually conceptualise groundwater across the area.
The geology is composed of interbedded Carboniferous age sedimentary rocks which have been folded, forming an asymmetrical anticline. Therefore, geological strata towards the east coast dip steeply to the east, whilst strata further west dip more gently to the south-southeast.
The Ballagan Formation and Fell Sandstone Formation located in the northwest of the area form a productive aquifer which supplies water to the local population. The Scremerston Coal Member which underlies the village of Spittal and village of Scremerston forms a complex, multilayered aquifer system comprising sandstone aquifer units separated by low permeability rocks forming aquitards. The Tyne Limestone Formation and Alston Formation in the east and south of the area also form a series of aquifer units and aquitards. Groundwater flow is likely to broadly follow the dip of the geological strata, potentially creating a groundwater divide through the area.
Superficial deposits include till, morainic and glaciolacustrine deposits, alluvium in the River Tweed and Allerdeanmill Burn valleys, river terrace, estuarine and glaciofluvial deposits around the River Tweed, beach deposits (sand, silt, gravel) on the coast, including under parts of Spittal. Till and glaciolacustrine deposits are likely to reduce bedrock aquifer recharge, whilst permeable alluvium, river terrace deposits, morainic deposits and beach deposits are conducive to groundwater recharge (or discharge), potentially forming small, perched aquifers.
Mine workings throughout much of the Scremerston Coal Member are likely to increase aquifer storage and potentially provide flow pathways connecting separate sandstone aquifer units. Some mine adits drain mine water into the North Sea and some workings extend under parts of Spittal, potentially increasing groundwater flow towards the village.
Groundwater level trends vary, with levels in the Fell Sandstone Formation and Ballagan Formation lowered significantly by abstractions. Groundwater levels and trends in the Scremerston Coal Member, Tyne Limestone Formation and Alston Formation are poorly understood due to a lack of data.
Groundwater flood risk is greatest in lower parts of Spittal where water likely discharges from sandstone aquifer units of the Scremerston Coal Member. Localised groundwater flooding is also possible in higher elevation areas where it emerges from aquifer units, fractures or perched superficial deposit aquifers.