Monday 11th November, 2019
It goes without saying that this autumn’s wet weather conditions will have had an effect on any work in and around rivers. For the Foundation, it meant that our “Larinier” pass construction at Ballsgate weir on the river Lugg could not be completed this year.
Usually the Lugg is relatively slow to react to rain. However, even it succumbed to the heavy downpours of early September, quickly rising to levels that were impossible for us to work in. These levels were sustained for much of the weeks to follow and the decision to bring the work to an end for 2019 had to be made on 6th October. Such is the nature of a rivers trust’s work!
The Need for a New Pass
Ballsgate weir is owned by the Environment Agency. It supplies a leat which runs a small, private hydro-electric unit and had a baulk fish pass built onto it some years ago (shown in the centre of the image above).
The problem was that this pass was only usable by migrating fish in just a few water heights. When combined with the large number of weirs to be negotiated downstream of Ballsgate, this narrowed the window for fish migration beyond it considerably. Often, numbers of salmon and trout redds could be found just downstream of the weir while large areas of excellent spawning and juvenile habitat upstream were relatively unused.
Ballsgate is the largest fish pass project the Foundation has undertaken and the first of a “Larinier” style.
Old weirs are unpredictable. Often, the water is flowing under and through them, as well as over the top. While securing the site and diverting the water with a coffer dam and inflatable bladder, we soon found Ballsgate weir to be extremely permeable!
In addition, we discovered that the sluice from which we were to build the fish pass off was built on sandbags with further work needed to under-pin it. Both of these issues put the construction behind schedule and the wet autumn then took away the chance for us to catch up.
It was disappointing for us to have to stop work early and leave the Larinier unfinished. However, the Foundation’s staff have learned a great deal from the project and are well equipped to take on such operations in the future.
More importantly, the benefit of such a wet autumn means that the window for migration on the Lugg will be much higher. We are hopeful that fish will ascend Ballsgate weir this year using the old baulk fish pass and utilise the upper Lugg catchment for spawning.
In the meantime, we will spend the autumn raising the funds required to finish the job next year!