From 1 April the Environment Agency will be using new aquifer designations that are consistent with the Water Framework Directive. These designations are aimed to better reflect the importance of aquifers as groundwater resources and also their role in supporting surface lakes, rivers and wetlands.
The new designations are based on the almagamation of the former NRA Groundwater Vulnerability maps and British Geological Survey mapping data. Aquifers are split into two different classes; those within superficial (drift) deposits such as sands and gravels, and those within bedrock (solid permeable formations) such as sandstone, chalk and limestone.
The new aquifer designations are:
Principal Aquifers - a layer of rock or drift deposits that have high intergranular and/or fracture permeability – meaning they usually provide a high level of water storage.
Secondary Aquifers – a wide range of rock layers or drift deposits with an equally wide range of water permeability and storage. Secondary aquifers are subdivided into two types:
Secondary A – permeable layers capable of supporting water supplies at a local rather than strategic scale, and in some cases forming an important source of base flow to rivers.
Secondary B – predominantly lower permeability layers which may store and yield limited amounts of groundwater due to localised features such as fissures, thin permeable horizons and weathering. These are generally the water-bearing parts of the former non-aquifers.
Secondary Undifferentiated – assigned in cases where it has not been possible to attribute either category A or B to a rock type. In most cases, this means that the layer in question has previously been designated as both minor and non-aquifer in different locations due to the variable characteristics of the rock type.
Unproductive Strata – rock layers or drift deposits with low permeability that have negligible significance for water supply or river base flow.
Further information and guidance on the use of the new aquifer maps can be viewed on the Environment Agency website