content@managingwater.co.uk Fish Passes & River Structures


David Noble. OBE spent a career spanning over 50 years in the flood defence and land


drainage business, within the public sector and in running his own specialist consultancy, including the provision of services to the Association of Drainage Authorities, acting as it's Chief Executive.


Structures in channels


- a foreword by David Noble


Channels, and particularly natural rivers and streams, fulfil a variety of functions, they were created to convey water to the sea the location of them dictated by topography and geology. Over hundreds of years channels have been adapted to serve other needs, notably on larger rivers the installation of water mills and the establishment of navigations have changed almost beyond recognition the characteristics of channels. In more recent times channels have been recognised as important habitats for fish, and in supporting invertebrates, together with a wide range of aquatic flora.


As development has changed the country’s landscape, channels have not escaped the impact, and other than in their headwaters the majority contain structures, which are in place for a variety of purposes.


In consideration exclusively of channel conveyance, and particularly of flood flows, it would be desirable not to have any weirs or culverts but they are necessary to accommodate other important interests, and where possible the adverse impact of their presence should as far as practical be mitigated.


Weirs, and other such barriers, across channels change the flow regime and dependent on the nature of the channel can have either a beneficial or detrimental impact on fisheries. Where they are in place to retain water levels in lowland channels for navigation purposes, it is beneficial in providing the ‘full’ river and water volumes to support the coarse fish population. They also provide the clear water favoured by the course fish anglers. In contrast those impeding the upstream progress of migratory fish are highly damaging.


Concern is expressed over the impact on the habitat due to another significant barrier to flow, namely the land drainage pumping station. Whilst all stations are protected with screens to avoid debris damage to the pumps the grid space is such that fish go through the pumps, and certainly the larger fish suffer. There is evidence that smaller fish can make that journey unharmed and indeed pass through complex pumped and piped systems to happily populate another water body.


Opportunities exist to mitigate the adverse impact of structures in channels and a good example is with the installation of fish passes within, or alongside, weirs. Whilst these have been in place for many years, more recently developments have provided pre-formed structures, which make installation very


much easier. 18 www.fadsdirectory.com


It’s not all flow meters and water quality you know!


Why fish thinking is key in the Water Utilities Sector…


Zebrina Hanley, Aquatic Control Engineering As with many new environmental legislations, our Water providers and associated contractors and suppliers are consistently given additional responsibilities to extract, distribute, filter, aerate, pump and more WHILST thinking about flood risk, drought, water quality, local ecology, invasive aquatic weeds…the list goes on!


A particular hot topic of AMP5 is thinking carefully about our fishy friends, and perhaps quite rightly so. Eel has declined by as much as 95% in our waters in the last 25 years and other fish populations such as sea trout are also dwindling in expected numbers. Although the exact cause of these declines is hard to pinpoint the Environment Agency, Institute of Fisheries and Angling Trusts all believe it is important that the entire water and environmental sector act to improve this now. Indeed their cries were heard and further legislation including the Freshwater Fish Directive, the EU Regulations and others have been updated and revised to cover recent concerns. Work in earnest has begun to re-think some long standing elements of the UK’s water flow control structures inland including culverts weirs, sluice gates and outfalls which are blocking migratory routes and now expectations for the industrial water sector to follow suit are beginning.


For the industrial water sector the legislation is beginning to clamp hard on intakes and any other related pumping. Whilst screening is commonly practiced, it is often insufficient at reducing fish mortality to acceptable levels as fish entrainment and disorientation still occurs. The focus is to keep fish away from flows which could potentially entrain them or to prevent smolts and small fish from entering through their first set of screens. The emergence of fish deterrent systems, using light and


sound as a dual solution with screening is now an important consideration for intakes and other similar applications.


Aquatic Control Engineering Ltd is a unique provider of fish migration solutions in industrial water abstraction applications including fish friendly hydropower, fish friendly axial pumping and fish deterrent strobe lights and acoustic systems. With in-house expertise from engineers,


environmental and fisheries educated employees, ACE is established at recommending, designing, project managing and installing these kinds of projects.


A popular solution, ACE fish friendly deterrent systems are installed close to pump inlets in sumps or in screens. A recent installation at Welches dam by Aquatic Control Engineering Ltd effectively prevents fish from entering by exposing them to bright stroboscopic light; fish sensitivity to this light causes them to seek an alternate route avoiding the dangers of the pump. This is an excellent solution for an intake refurbishment where pumps are already installed.


For new build projects fish friendly axial pumps can be installed allowing pumping and safe fish passage simultaneously. Installed in Holland, independent testing by consultants Witteveen and Bos awarded these pumps with a 100% fish friendly status (study in Dutch and English available upon request).


If you are working on a utilities construction projects, are involved in environmental utilities work and would like more information, please do not hesitate to contact us at any time.


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