U.K. Debates a Barrier on the Severn
by Erica Gies
CARDIFF, Wales — The Severn Estuary, dividing southwestern England from South Wales, is an area of outstanding scientific and environmental interest, a designated conservation site under the convention on internationally important wetlands signed in Ramsar, Iran, in 1971, with special protection under European Union bird and habitat directives.
Tides rolling from the Atlantic Ocean are funneled up the Bristol Channel into the rapidly narrowing estuary, creating a tidal system with a range of as much as 14 meters, or 46 feet, between high and low water, the second biggest in the world after the Bay of Fundy, in Nova Scotia.
Global warming, energy security concerns, and rising oil and natural gas prices have prompted the British government to reconsider proposals, first dreamt of more than 150 years ago, and last rejected in 1989, to harness the energy of the Severn’s tidal surge.
Last month the government’s secretary for business, John Hutton, announced terms of reference for a two-year feasibility study to re-evaluate options for generating electricity. They include the building of a huge barrier running 10 miles, or 16 kilometers, across the estuary, and smaller-scale alternatives like a set of “tidal lagoons” — offshore catchment pools that would allow energy to be harvested from impounded waters without blocking the entire river mouth.
The aim is to narrow the field down to a specific project — or decide that none is worth pursuing — by September, with the rest of the time spent on examining issues raised in greater detail.
Debates surrounding the study highlight the conflicting ecological and economic priorities confronting the government as it seeks to chart a new course for Britain’s energy industry.
The British government and the devolved authority for Wales, the Welsh Assembly Government, have set ambitious renewable energy targets. Britain aims to generate 40 percent to 45 percent of its electricity and 15 percent of its total energy requirements from renewable sources by 2020. Wales is aiming for self-sufficiency in renewable and low-carbon electricity by 2025.
These goals illuminate why the government is reconsidering a project calculated to cost more than £15 billion, or $29.5 billion, and take 14 years to complete. The largest proposal, spanning the mouth of the estuary downstream from Cardiff, in Wales, and Weston super Mare in England, could generate up to 8,640 megawatts of electricity and meet 4.4 percent of Britain’s current annual electricity demand, according to a report issued in October by the British government’s Sustainable Development Commission.
“Harnessing the Severn will produce a long-term renewable energy source for Wales and also the U.K.,” said Jane Davidson, the environment minister in the Welsh assembly.
Still, that would represent just 0.6 percent of total energy consumption in the country, and would reduce Britain’s carbon emissions by less than 1 percent, according to the commission’s report.
“The barrage is an extraordinarily expensive way to reduce carbon emissions,” said Morgan Parry, head of the wildlife conservation group WWF Wales, referring to the proposed barrier. “By some estimates, it’s 10 times more expensive than other carbon-abatement methods.”
Neil Crumpton, an energy campaigner in Wales for Friends of the Earth, said: “For just 1 percent of our energy, we don’t think we should damage one of the largest, most heavily protected wildlife sites in Britain.”
Environmental groups have taken a stand against a Severn barrier, citing concerns that run chiefly along two tracks. One is protecting the unique habitat that even government and industry agree would change drastically with a barrier. The second is that time and money spent building a barrier would be better invested reducing carbon emissions by energy efficiency and other renewable energy technologies.
The commission’s report stipulated that any Severn tidal project must conform with EU directives requiring the creation of a compensatory habitat to replace breeding and feeding grounds lost to development.
But Alun James, a senior Welsh energy official, said that a compensatory habitat would not have to be near the original area that it replaced. It could be anywhere in Britain.
Many environmentalists question the usefulness of such substitute habitats for the bird and fish species that would be put at risk by a barrier.
Parry, of WWF Wales, said migratory allis and twaite — two herringlike fish species — spawn in Britain only in the Severn’s tributaries, making it nearly impossible to create alternative habitats for them.
“Strictly under the habitat directive, we think that would mean that building a barrage would be illegal,” he said.
Even if creating alternative habitats were technically possible, more than 14,500 hectares, or almost 36,000 acres, would be required for birds alone, costing £600 million to £1 billion, according to Peter Jones, environmental policy officer at the Royal Society for the Protection of Birds.
The commission’s report looked at other barriers to see how local environments were affected. The Rance barrier, built in Brittany, France, in 1966, is the largest in the world. Still, at 240 megawatts peak output, it is a tiny fraction of the size of the Cardiff-Weston proposal.
Dominique Melec, head of the Comité Opérationnel des Élus et Usagers de la Rance, an association for sustainable development of the Rance estuary, said recently, “The Rance barrage has inevitably caused some changes in the local environment.” But he added that much of the initial ecological damage had resulted from the harsh construction methods employed, including drying out part of the estuary for three years. During that time the river was completely closed off from the sea, with consequent loss of salt-water species.
Once construction was completed and the barrier sluices were reopened, the ecosystem of the Rance estuary had recovered a “more or less satisfactory” equilibrium after about 10 years, he said.
Severn barrier advocates say that, with tidal action blunted, the water behind the barrier would be clearer, allowing a greater quantity of aquatic life than what currently thrives in the severe conditions of a hyper-tidal estuary.
Environmentalists say more life is not the point. “What would be lost would be the species that are, at least in this part of Europe, relatively rare, and certainly would become rare if they lost their habitats from the Severn Estuary,” Jones said. “What we’re concerned about is protecting a unique environment.”
An even smaller barrier sits in a similar tidal ecosystem in the Bay of Fundy. In 1984, a tidal turbine was installed in an existing causeway, to generate 20 megawatts of electricity. According to Anna Redden, a marine scientist who directs the Estuarine Research Center at Acadia University in Nova Scotia, it is the 48-year-old causeway that has caused the most significant environmental disruption, not the turbine.
Matt Lumley, communications advisor for the Nova Scotia Department of Energy, said Canada has shelved consideration of barrier power in favor of testing in-stream tidal devices — machines like underwater windmills that have environmental and economic impacts that are much lighter than those of barrier technology. Britain is also considering tidal stream technology for other areas.
Redden said tidal turbines in barriers could be rendered useless by sedimentation. “In highly tidal areas, there’s usually a lot of sediment,” she said. Studies in the 1970s revealed the folly of a proposed Cobequid Bay barrier in the upper reaches of the Bay of Fundy. “They discovered the sediment would build up incredibly, and the lifetime of these turbines within a barrage would be very short,” she said.
The Rance barrier changed currents in the estuary, Melec said, and “it took about 30 years to establish a new sedimentary equilibrium.” For the Severn, he said a lot would depend on the types of sediment and the underlying geology of the estuary.
The EU’s habitat directive requires that if a project will have an impact on a designated species’ habitat, developers must show that no less environmentally damaging alternative is available.
Environmental pressure groups question if a Severn barrier can meet that requirement, contending that energy needs can be met by greater efficiency and by less damaging microgeneration, wind, solar, in-stream tidal, biomass, and related technologies. These could be deployed faster and could reduce carbon emissions much more than a barrage, they say.
“Far more needs to be done between now and, say, 2014 or 2015, when the level of atmospheric carbon dioxide is likely to pass 400 parts per million,” said Jones. A concentration of about that level is regarded by many scientists as a critical threshold in the struggle to curtail global warming.
Friends of the Earth, which favors a tidal lagoon solution, is concerned that the totally untested technology may not be given equal consideration in the government’s feasibility study. In January, the government offered increased incentives to industry to build an experimental demonstration lagoon. But for regulatory reasons at least, it is unlikely to be ready before the first decision target date in September.
Davidson, the Welsh minister, has pledged that the feasibility study will weigh all alternatives evenhandedly.
Among the strongest backers of a barrier solution is the Severn Tidal Power Group, a coalition that includes four of the top British engineering and construction companies, and has been lobbying for a Severn barrage since 1984.
Roger Hull, spokesman for the group, said, “We need to adopt all methods of carbon reductions that we can let our hands on. We can’t afford to turn away any of these options unexamined.”
For Parry, of WWF, that argument is flawed. While carbon reduction is essential to curb climate change, he said, “we also need to ensure that our natural systems function properly and without obstruction.”