A revised hydrogeological conceptual model of the Fell Sandstone aquifer, Northumberland and its impact on the interpretation of long-term nitrate trends

Abstract

Northumbrian Water abstract groundwater from the Fell Sandstone Formation (part of the Carboniferous Border Group) in north Northumberland, which is a groundwater-only water resource zone providing drinking water to Berwick-upon-Tweed and the surrounding area. Groundwater in observation and abstraction boreholes shows significant rising nitrate levels derived from agricultural land use, and are predicted to have an impact on groundwater quality by 2030. Northumbrian Water policy is to use catchment management techniques to mitigate rising nitrate levels through influencing land-use practices and reducing nitrate concentration in groundwater recharge. This paper demonstrates how a detailed geological and hydrogeological understanding of the area has been used to identify specific areas where appropriate catchment management techniques may be most effectively applied. Northumbrian Water and the Environment Agency jointly funded the British Geological Survey to develop a numerical groundwater model of the Fell Sandstone aquifer and to undertake a review of the geology of the Fell Sandstone Formation as part of a Water Industry National Environment Programme (WINEP). Combining the results of these two studies, supported by spatial and temporal field measurements of groundwater nitrate levels, an improved understanding of the potential fate and transport of nitrate in the Fell Sandstone aquifer has emerged. This allows a better prediction of the spatial and temporal impacts of nitrate losses from the soil zone to the aquifer in support of a catchment management approach to mitigating rising nitrate levels. Thematic collection: This article is part of the Hydrogeology of Sandstone collection available at: https://www.lyellcollection.org/cc/hydrogeology-of-sandstone