Stour Estuary

Alton Water Reservoir Pressures

The table below shows the current pressures that this waterbody faces and the solutions that could be put in place to solve these problems. You can learn more about some of these pressures and solutions on the Environment Agency Catchment Data Explorer or you can contact us to find out more.



    Diffuse pollution




    Physical modification


    Fish passage


    Invasive species


    Point source



A combination of all of the previous pressures, and the general maintenance of the river, means that the morphology of this river is classified as moderate.

Much of the modification in this waterbody cannot be changed due to required structures.

Maintenance can be more considerate to wildlife and structures can be made to incorporate more natural features such as bankside vegetation.

There are multiple structures in this waterbody which prevent fish movement. There is a 1.7km stretch beyond the reservoir where the fish population has become completely isolated over the last 10 years. Isolated populations are often more susceptible to disease and other pressures.

This pressure can be solved by improving structures to allow fish and eel passage.

Increasing habitat for fish where these structures are in place would also be beneficial.

Flow is heavily impacted in this waterbody because of two main factors. One is the impoundment of water at Alton Reservoir. The second is a flood protection structure which also affects the natural flow of water. The reduced flow means that the dissolved oxygen content in this waterbody is at poor status.

This waterbody has now been re-designated as heavily modified which means that it can be re-assessed taking these structures into account. Unfortunately, both the reservoir and flood protection structures are required and therefore need to be maintained. Ensuring the establishment of vegetation to maintain habitat availability is the only step that can be taken.

Website key stakeholders:

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Design by LTD Design Consultants and build by Garganey Consulting based on an original concept by Herts and Middlesex Wildlife Trust