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Hydropower

What is the Authority’s policy on hydropower?

One priority in the Authority’s Partnership Plan for 2012-2017 is to make progress towards becoming a carbon-neutral National Park. In pursuit of this priority, the Authority is keen to encourage renewable energy schemes where consistent with the purposes of the National Park. Renewable sources include wind, photo-voltaic, biomass and hydropower. Aside from the green benefits, the financial incentives now available from central government can make renewable energy generation an attractive investment for private developers and communities. 

The Exmoor Local Plan provides the planning policy background. Policy LNC17 is positive in terms of the provision of small scale renewable energy schemes where they are compatible with the conservation of the landscape and wildlife of the National Park. 

This note provides some background to those contemplating hydropower schemes and gives sources of further advice.

What is the history of hydropower on Exmoor?

The combination of Exmoor’s topography and high rainfall provide opportunities for hydropower. In the past, numerous mills were built for purposes such as grinding corn and sawing timber. Public demonstrations of the Authority’s sawmill at Simonsbath give a good idea of a traditional mill in action. For details please see the events page here.

On Exmoor, the most successful electric hydro scheme to date was built in 1983 in the West Lyn Gorge at Lynmouth. This has a power output of 300 kilowatts, and each year generates 1.5 million kilowatt-hours of energy for the grid. The visitor centre there includes much of interest, including working models. 

Recently, the West Lyn scheme was granted a licence to increase the energy generated.

On a smaller scale, one of Exmoor’s traditional mills has recently been converted to hydropower generation. And there are micro-scale hydro schemes in operation and under development on some of Exmoor’s fast-flowing moorland streams.

Much earlier, back in the 1890s, a hydropower plant was built on the East Lyn River to supply electricity to properties in Lynmouth. It was eventually destroyed in the devastating Lynmouth flood of 1952. Little remains of the old scheme: the intake sluice, part of the leat and pipeline, and – some way downstream of its original location – a block of masonry weighing some 15 tonnes. That illustrates the immense power of water, and also explains man’s attempts to harness it. Recently, a new hydropower scheme was proposed for the East Lyn but this failed to proceed because of unfavourable economics and concerns about the environmental impact.

Early in the 20th century, the Dulverton Electric Lighting Company built a hydropower plant on the River Barle at Beasley Mill. This 100 kilowatt plant continued to generate electricity for lighting until 1938 when Dulverton was connected to the national grid.

A more enduring application of water power is the spectacular Lynton and Lynmouth cliff railway, built in 1890. It uses gravity and water diverted from the West Lyn River to drive the funicular railcars.

Water was also used to drive the machinery in a mineral water bottling plant at Lyn Rock on the East Lyn River between 1911 and 1939. This scheme was washed away in the 1952 flood.

Is my river site suitable for a new hydro scheme?

The basic requirements are flow volume and ‘head’ - the vertical drop between intake and turbine. A new low head, high flow scheme on a river would entail building a new weir to divert the water through the turbine. Where salmon (and sea trout) are migrating up and down the river, a weir would introduce a new barrier to migration. Such movements are essential to the salmon life cycle, and are protected by national and international legislation. Because of the likely adverse effects on the environment, the Environment Agency is “unlikely to approve the construction of new weirs solely for hydropower on lowland rivers. This also applies to the reconstruction of weirs that have ceased to be serviceable” . Schemes entailing new weirs are therefore unlikely to be consented on these types of rivers on Exmoor.

What about converting an old watermill on an Exmoor river?

Traditional watermills on rivers are typically low head, high flow, and in theory some of these have scope for conversion to electricity generation. However, for new hydro schemes on existing weirs, the Environment Agency’s guidance, currently in draft, is likely to be highly restrictive. Where an existing, damaging abstraction or barrier can be ameliorated by fish-friendly measures combined with a hydro scheme, consent is more likely to be forthcoming. 

Surely some moorland streams have potential for hydropower?

Indeed they do. Exmoor’s steep moorland streams and high rainfall, combining low flows with high head, can offer workable, economic schemes. Recent and current hydro installations in the Exmoor National Park are almost all of this type. Whilst some such streams are tributaries of Exmoor rivers’ salmon habitats, many are not. Proposals on these - and others not in scheduled areas - are likely to be considered less sensitive, making for simpler engineering, licensing and consent. Information about existing and newly consented schemes within the National Park is available from the Planning Section at the National Park. Joe White, Principal Planning Officer – Development Management is the first point of contact at jiwhite@exmoor-nationalpark.gov.uk.

What about specialist advice on engineering and economics?

Even small hydro schemes are technically complex and extremely site specific: the engineering design needs to be tailored carefully to each particular site, its topography, geology, flow and ecology. Property owners with sites of possible interest are advised to use professional chartered engineers with experience of this kind and scale of work. Before appointing your engineering consultant, it may be sensible to visit some of their previous projects and speak to the scheme owners yourself. 

Riverine civil engineering projects on steep ground of highly variable geology (Exmoor being a spectacular example!) almost always encounter some kind of unexpected conditions; it is therefore normal practice to add a large contingency sum to the early cost estimates. 

It is advisable to check the physical and economic feasibility of the scheme before spending too much money. Don’t be surprised when this entails evaluating alternatives, and some re-work and interaction between engineering, economic and environmental considerations.

A key parameter is the amount of water you are permitted to take, and conversely the amount you must leave to flow down the normal watercourse – the 'Hands-off Flow'. This is fundamental to the scheme design, its operation and the ecological impact, so early informal guidance should be sought through the Environment Agency’s website, given in the next section. 

On small schemes especially, the preliminary work up to the receipt of licences and planning permission will be a significant proportion of the total cost. This expenditure will necessarily be ‘at risk’ if the scheme does not proceed.

A useful technical introduction to small hydro is provided by the British Hydropower Association, and can be found here.

What consents are needed?

Planning permission will need to be sought from the Exmoor National Park Authority. You will also need licences and consents from the Environment Agency for abstraction (even though you are putting the water back downstream), impounding and separately for the flood drainage implications. The Agency’s web-page for hydro can be found here.

It is likely that your abstraction licence will require you to carry out regular monitoring, measurement and reporting of the scheme in operation.

The licence will also specify the Hands-off Flow, and also the Maximum Flow that you can abstract. Current guidance is that the maximum permitted abstracted flow is equal to the mean flow. However, the flow limits in the Environment Agency’s Good Practice Guidelines for hydro have been under review and consultation for three years. It is expected that the Agency will publish new flow conditions in the near future.

Several potential sites on Exmoor lie in areas protected by National or European designations such as Site of Special Scientific Interest and Special Area of Conservation. Schemes in such areas need consent from Natural England. Locations of SSSIs and SACs can be found here

The legislative protection of salmon has been mentioned above.

On Exmoor, there are numerous Scheduled Ancient Monuments: a scheme close to any of these will need consent from English Heritage. The historic environment is also an issue considered in the planning process; the Authority’s experts in this field will be happy to advise if your site is clear of sensitive areas.

With a planning application it may be necessary to accompany it with an Environmental Impact Assessment. This will detail all the issues and set out the investigations and alternative options that you will have worked through leading to the submitted scheme. 

What investigations and surveys are needed?

Even on undesignated sites, the authorities will require an ecological investigation. This will need to cover the scheme’s impact on flora, fauna and migratory fish, preceded by a baseline study of the status quo. It will be necessary to employ consultants with the width of expertise to cover all of these specialisms and it is probable that more that one firm of consultants will need to be involved. And they will probably be different again from the consultants who do the engineering design. 

Considerations of engineering, scheme economics and, of course, ecology will need water flow data, which usually means collecting flow measurements over a year. A weir for flow measurement will itself need Environment Agency consent.

The engineering designers are likely to need a ground investigation to assess levels of bedrock and the engineering properties of the ground above.

Your designers will also need to consider the visual and landscape impact of the scheme, and some informal discussion with the Authority’s planners is advisable at a very early stage and long before you make a formal planning application.

Apart from the regulators, who should I consult?

If you do not own the entire site, early consultation with the owners of the river bank and those with the fishing rights (not always the same) is advised. Early liaison with upstream and downstream fishing interests is also advised, as these are affected by a scheme anywhere on the river due to the migratory nature of the fish life cycle.

Fishing interests are sometimes thought to be hostile to hydropower schemes and with early discussion involvement this need not necessarily be the case. For instance, it is understood that The South West Rivers Association and its constituent river groups have supported more hydro schemes than they have opposed.

There are a number of local Exmoor river bodies that have considerable knowledge of an individual river and may help to ensure that you are in possession of as much information as possible before you consider spending time and fees working up a proposal. 

The Exmoor Rivers and Streams Group is an umbrella group of these local river bodies and have advised the Authority on implementation of river aspects of the Partnership Plan, and can:- 

  • put you in touch with individual members with detailed local knowledge of particular rivers and their habitats, 
  • help to identify win-win opportunities for combining power generation with habitat improvement, and
  • help you to contact owners of the river bank and fishing rights. 

To tap into this local knowledge, you may wish to get in touch with:

Richard McLaughlin, Exmoor Rivers and Streams Group,
ERASG member for hydropower
deercomberichard@gmail.com

We are planning a community hydro scheme: what do we need to think about?

Those contemplating community schemes should acquaint themselves with – and consult – all the affected property and riparian interests. Community schemes entailing grant funding from public sources and charities will need to have credible structures for governance, supervision, project management, financial control, consultation and reporting. 

Where can I get impartial expert advice?

On the Devon side of the National Park local independent advice for community schemes and private developers is available from Devon Association for Renewable Energy.  

In Somerset the Centre for Sustainable Energy may be able to advise or recommend an independent consultant to assist.

What incentives are available for hydropower on Exmoor?

Government incentives for small-scale hydropower are currently available. These are not in the form of a grant; instead, under the Feed-in Tariff, you would receive a payment for the power you produced, whether you use it yourself or sell it. 

Further information is available at the Energy Saving Trust.  

In addition if there are benefits to the National Park there may be grants against capital cost available from the Exmoor National Park Partnership Fund.

What else do I need to think about?


Exmoor has considerable potential for hydropower schemes. Successful project outcomes, avoiding damage to the environment and landscape, will always depend upon careful consideration of all the implications, with appropriate advice from expert consultants and the sources above. Such advice should help distinguish at an early stage those schemes with realistic potential from those which are unlikely to be viable. This will avoid needless cost and disappointment. If you believe that you have a scheme that can meets the various requirements then we are very happy to have a discussion on the planning merits and put you in touch with other bodies such as the Environment Agency and Natural England.