28. Improving fish movement along the Mimram

Theme: Water Quality, Habitats and Wildlife


  • That whatever the flow level, the river and its associated habitats, including banks and floodplains, are managed to support chalk stream species

Project description

To ensure the river is passable by fish along as much of its length as is feasible

Over the years lots of weirs and obstructions have been put in the Mimram for mills, water management etc. However, many of these restrict the ability of fish to move between sections. This can impact on their lifecycle, and also restricts the genetic diversity of fish populations. 

Good fish passage is one of the key criteria in meeting the EU Water Farmework Dirctive's Good Ecological Status (GES) and this is one of the reasons the Mimram is currently judged to be 'Poor Status'.
There are a number of options, including removing or lowering the weirs completely, or installing ‘fish passes’ on them. Removing or lowering weirs will also have knock-on benefits upstream, by reducing the ponding effect of weirs, and therefore reducing siltation above them and potentially also lowering flood risk upstream.
Some weirs will be impracticable to move or bypass, and in other cases it will not be desireable.

The project will aim to review each weir to determine whether it would appropriate and if so, the most best approach.


Project lead: Environemnt Agency
Project partners: Environment Agency; Landowners; Herts & Middlesex Wildlife Trust; Friends of the Mimram
Project start: 2013
Contact for more information: Sarah Scott, Environment Agency
Enabling fish movement along the Mimram

Design by LTD Design Consultants and build by Garganey Consulting.