Fish Passes on River Abstractions/Impoundment Structures

September 15, 2020

If you are planning to construct a structure that will obstruct a know migratory route, you will need a fish pass.

The free passage of migratory fish is a key requirement of the Water Framework Directive. Installing weirs, dams, culverts and other obstructions in waterways to manage river abstractions, can cause disruption to the movement of fish and other aquatic fauna. SEPA, the Environment Agency and Natural Resources Wales have a range of statutory powers to improve fish movement to support and promote the diversity and abundance of fish and eels in our watercourses.


Do I need to install a fish pass?

If you plan to construct, a weir to manage river abstractions, and it obstructs a known migratory route, then the simple answer is yes. If you operate an existing impoundment structure, then you could be required to install a fish pass. If you already have a fish pass in place, maintenance and ensuring its fit for purpose are likely to be your responsibility.


What are the options? 

There are several factors to consider when designing, installing and maintaining an effective fish pass. Each river system is different; therefore, knowledge of the hydrology, geomorphology and suitable engineering solutions are required. Solutions that require in-river works will be subject to several regulatory considerations, potentially including:



A high level of regulatory liaison will be required to ensure that the requirements of operators are balanced against regulatory requirements, particularly where works are planned on statutory main rivers. Importantly, the final solution must take account of the practical and financial considerations associated with any in-river works.


Our surface water team are uniquely placed to help you assess any requirements for improving fish passage and liaising with the regulators to achieve the most appropriate solution. If you are interested to learn more, get in touch with our technical lead, Lee Clarke at LeeClarke@envireauwater.co.uk or call us on 01332 871 882.


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