Aire Rivers Trust has agreed to fund work to improve fish passage and reinstate connectivity on several small to medium-sized weirs on tributaries between Bingley and Malham. The work is being coordinated by Professor Jonny Grey, Research & Conservation Officer for the Wild Trout Trust, in partnership with the Environment Agency and various other organisations and land-owners.
Ideally, these redundant weirs would be removed completely to reinstate a more natural channel form and flow of water, plus transport of material (cobbles / gravel) downstream, and reduce flood risk. However, other surrounding infrastructure that potentially could be affected by complete removal requires some thought. The proposed solution at each weir varies slightly because of the differing nature of each beck and immediate environs. Most will be ‘notched’ in some format, i.e. the crest of the weir will be lowered in a specific location to create a focus of flow during low flow conditions.
Eastburn Beck has been a particular focus for related work (see blog post, here). The last in a series of privately owned weirs just below Glusburn Bridge was notched in May. Jonny noted that there were trout fry in abundance during the works – a good sign of the population bouncing back from the previous year’s unprecedented flooding that effectively scoured out all the eggs and juveniles. The weir owner was delighted! The notch will allow them better access both up and downstream, and also reduce the amount of stagnant water and silted sediment upstream in the formerly impounded section.
Kirkby Beck is much smaller than Eastburn, and much higher in the Aire catchment at Hanlith. The weir is less than 10m upstream from the confluence and hence is an immediate obstruction on the system. The local farmer agreed to a notch and several hundred metres of fencing to prevent livestock access from degrading the beck banks, thereby improving the habitat at the land water interface for birds, mammals, insects and plants, as well as fish. The work was carried out in May when the beck had all but dried up! The aquatic organisms living in such ephemeral streams have evolved to cope with occasional dry periods in all sorts of ways; with a notched weir, now the fish can recolonise more easily after having migrated downstream to avoid the low flows.