Aquatic Control Engineering

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Siphon Fish Pass @ River Wissey, Norfolk

The Siphon Fish Pass, developed in the Netherlands, is an innovative fish passage system based on the traditional pool and weir fish pass. The Siphon Fish Pass can be utilised to provide migratory fish passage at many natural or manmade watercourse obstructions including weirs, lock structures, sluices and even between different watercourses. The Siphon Fish Pass can allow passage of most types of fish, varying from small coarse fish and eels to large migratory salmonids without compromising any existing flood defences.

For this project, Aquatic Control Engineering Ltd acted as principle contractor under the CDM regulations on behalf of the Environment Agency to design, supply, install and commission the UK’s first Siphon Fish Pass. The site is located in Stoke Ferry, North Norfolk at the Wissey Syphon diversion sluice. This structure consists of large counterbalance gates, one of which prevents the free-flow of water (and thus fish migration) between a cut-off channel and the River Wissey.  Although an important flood defence structure for local residents and land owners, the structure acts as an impassable barrier for coarse fish, salmonids and eels.

The Siphon Fish Pass was chosen as the most appropriate solution for a number of reasons:

1. The siphon provides fish and eel migration in both directions between the two water courses
2. The siphon at the Wissey site is partially buried allowing easy integration into the existing landscape without the need for hard engineered foundations.
3. In times of high flows the siphon can be shut down and isolated to remove any risk of flooding.
4. Utilising the natural siphon effect, power and water consumption is kept to a minimum
5. A unique design requiring minimal civil engineering makes the siphon substantially cheaper than other traditional options

The Siphon Fish Pass, available from ACE is adapted technology from Holland.  This already hugely successful Fish Pass has been modified to be compliant with the Environment Agency regulations. 

Each site presents a unique obstruction, the adaptive Siphon Fish Pass system can be designed to take into account; flow, head differential and of course expected fish species.  This Wissey Siphon Fish pass project was completed from initial site visit to commissioning in just nine months.  This is testament to careful planning, hard work, strong teamwork and a truly innovative product.   

For more information please see our Siphon Fish Pass product information page.  Also we held a lunch event and more detailed information is available on the dedicated event page, which also features our presentation slideshows