The Environment Agency commissioned ESI, now part of Stantec, to develop the Cotswolds conceptual and numerical groundwater model.
The Jurassic limestone aquifers of the Cotswolds are an important source of public water supply, as well as supplying baseflow to the headwaters of the River Thames.
However, these karstic aquifers have low storage potential and respond rapidly to rainfall. During dry periods many reaches of the main tributaries may become dry naturally, which makes the aquifers particularly vulnerable to the effects of over abstraction.
The Environment Agency needed to develop a conceptual and numerical groundwater model of the area to provide a sound evidence-based tool. This would then support their strategic assessment of the available water resources and water abstraction licensing decisions.
The model would also help to develop measures to protect the groundwater in these aquifers very vulnerable to pollution, due to the speed with which recharge reaches the water table after rainfall.
In 2011 ESI was awarded a contract to develop the Cotswolds conceptual and numerical groundwater model.
The hydrogeology of the area is considered to be particularly complex and challenging due to the faulted, layered and karstic nature of the aquifers.
ESI put forward a strong team with a track record in water resource hydrogeology, modelling of layered and fractured aquifers as well as relevant experience of the Jurassic Limestones.
Following a thorough review of the available data to develop a detailed conceptual model of the area, ESI developed a multi layer groundwater model of the core study area. A pragmatic approach to model design meant that unnecessary complexities were avoided and the calibrated model was able to simulate observed flows and trends in groundwater levels accurately.
This combination of a pragmatic approach with a team with very strong modelling skills resulted in a successfully calibrated groundwater model which is now being used by the Environment Agency and Thames Water to assess the extent and significance of abstraction on the local water resources.