Chalk Streams

Project Highlights so far:

Instream improves on the Chalgrove Brook and Kingsey Cuttlebrook
Fish passage and habitat improvement at Cuxham Mill
Detailed water quality investigations at 3 sewage treatment works
Mapping of potential restoration opportunites in chalk tributaries

Chalk streams are a special type of spring-fed river unique to England and northwest Europe.

Chalk streams derive most of their flow from underground chalk aquifers. The chalk aquifer and the chalk landscape are historically, aesthetically and ecologically distinctive because of their alkalinity, minerality and their cool, stable and gentle flows, which support a rich ecology and biodiversity.

The chalk aquifer acts like a vast sponge, soaking up rainfall over the winter months, releasing it slowly through the summer.

Only a small proportion of flow reaches a chalk stream by surface run-off. This creates a stable flow-regime with the stream comparatively buffered against the extremes of wet weather and drought compared to run-off dominated rivers.

The River Thame Chalk Stream Strategy applies to all tributaries to the River Thame arising in the Chilterns (e.g. Chalgrove Brook, Lewknor Brook, Cuttle Brook, Kingsey Cuttlebrook, Scotsgrove Brook, Stoke Brook, Wendover Brook and Upper Thame rising in the chalk).  

These are “scarp-face” chalk streams, which rise at the base of the chalk and tend to flow out onto the greensand beds and the underlying clay.

Objectives to achieve over the coming years as part of our Chalk Stream Strategy:

The scoping process for our chalk stream strategy was completed in 2022/23 with support from the rivers specialists at Atkins and funding from Natural England's Seedcorn Fund. The process identified significant restoration opportunities across each of the chalk stream catchments to improve habitats, expand connectivity, monitor, engage and improve practices amongst polluters.

The ultimate objective is to restore habitats and water quality to a level that would enable the recovery of characteristic chalk stream plant and animal communities.

Currently, our priority chalk stream tributaries are...

The Chalgrove Brook which hosts our only verified population of wild brown trout.

The Cuttlebrook which is the only tributary free from sewage discharges.

The Kingsey Cuttlebrook which has stretches of excellent habitat and hydromorphology but constraints from water quality.

Thank you to:

Our Funders: Environment Agency, Natural England, Chilterns Conservation Board and South Oxfordshire District Council
Our Partners & Suppliers: Atkins, Chiltern Rangers, Rivers Trust, Nature Metrics, UK Centre for Ecology & Hydrology, Babylon Plants, Cuttlebrook Nature Reserve Volunteers

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