EcoSF4: Judas Gap Fish Pass Detailed Design

Judas Gap is an Environment Agency owned structure located at the saline limit on the River Stour on the Essex Suffolk border, NGR TM0799732809. The site already has a pumped eel pass installed in the old fish pass chamber.

The Judas Gap structure is critical in terms of fish movements for the Stour, for both freshwater fish that are trapped on the downstream side and migratory fish that require an entry/exit route to the freshwater system, both smelt and sea trout are present in the Stour estuary. The design will also need to ensure that eel passage is maintained.

The River Stour has an augmented water supply from the Ely Ouse to Essex Transfer Scheme (EOETS), water is pumped from the Gt Ouse to the top of the rivers Stour and Pant. Located in the Lower Stour is one of the main water supply abstraction points at Cattawade Intake, Essex and Suffolk Water (ESW) abstraction licence number 8/36/15/*S/0123, NGR TM1004933059. Work has been undertaken in the latest round of the Water Industry Natural Environment Programme (WINEP) to ensure flow continues down the Lower Stour and North Channel during low flow conditions, rather than being abstracted from the middle reaches of the Stour, this has been implemented to prevent large scale fish mortalities and wider ecological harm in this section of the river, the EA has worked with ESW to secure 5mld for the operation of a fish passage solution in this section. The requirement to impound water in this section of the river for public water supply abstraction inhibits the possibility for barrier removal. This section of the River Stour is also a navigable waterway.