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Severn Barrage

My Lords, I am delighted that the noble Lord has had the will and the luck to secure this debate. When I was in another place, our constituency boundary to the west was the middle of the Severn, from Sharpness to Avonmouth. During my time as an MP, great studies were done on the possibility of a barrage, and I followed them closely and met many of the people involved. Since then, of course, global warming has added considerably to the case for trying to exploit the tides. The exceptional tidal range on the Severn should not surprise anyone. If you look at the map of south-west Britain, you can see the huge funnel into the estuary between South Wales and Devon and Cornwall. That funnel faces directly out into the Atlantic Ocean, and the huge volume of water in the ocean is pulled backwards and forwards, primarily by the Moon’s gravity, to produce the tides. That huge volume swirls up the estuary and is then sucked out again twice daily. The ebb tide is reinforced by the fresh water coming down from the Severn and its tributaries—it is after all the longest river system in the country. The highest tide this year was in March, when the difference in height between the high and low tides at Avonmouth was 14.3 metres, which is about a foot higher than the ceiling of your Lordships’ Chamber. If noble Lords imagine a wall of water as high as your Lordships’ Chamber and several miles across coming and going twice a day, they will have an idea of the power which a barrage or the other facilities would be designed to tame. Of course, the height of the tide varies during the month and during the year, but the mean range between high and low tide at Avonmouth is 8.2 metres. Even on that basis, the Magna Carta Lords depicted above us would get their feet wet twice a day. It is clear that we must, as I am sure we will, harness that awesome natural power. There are various ways of doing so, as the noble Lord made clear, some of which could be pursued simultaneously, as they are not all mutually exclusive by any means. The barrage is only one way, albeit the biggest and most powerful, but it would involve some very large problems. I believe that we need to assess those problems once again and then decide—and the sooner we do so, the better. The problems that would be entailed are well documented in studies over many decades. They need updating but it would by no means be wholly new work. First, there is the enormous scale of what we are considering. The front-runner among the various barrage configurations—the Cardiff to Weston barrage—would be 16 kilometres long and would cost nearly £1 billion a kilometre, according to one estimate, which is half of the whole defence budget. The actual technology is not that complicated or advanced but the problems of construction in such a harsh environment are considerable: imagine holding back that amount of water when the barrage is half-built and you are trying to close the gap. I watched the building of the second Severn bridge. It is one of the greatest engineering marvels of recent years and should, incidentally, be much more widely appreciated than it is, but it gives an idea of the challenge. The noble Lord, Lord Livsey, mentioned the French barrage at La Rance. It is true that it is currently the largest tidal barrage in the world, but the Severn barrage, by capacity, would be 36 times its size. It is on a quite different scale. The habitat problem is well known and will clearly loom large in any decision. However, I want to draw attention to two of the other important factors. One is the problem of the timing mismatch between the generation of electricity by a barrage and the peak demand for electricity. On some days, generation and demand will coincide but on many they will not. The barrage would be expected to generate during most of the time that the tide was ebbing, but the output would vary even during the times of generation. The times when the barrage would be generating are calculable with precision well in advance but they cannot be chosen. The barrage will produce electricity when it wants to, when the tide allows. The SDC says that that is not a technical problem for the grid—it is less of a problem, for example, than fluctuations in wind power—but it is an economic problem. It means that electricity produced by the barrage must comparatively be so cheap that the other sources can be rested with advantage when the barrage is working. For a project of this scale, that is a high hurdle to overcome. The other problem is the silt. The river always looks extremely muddy and that is because thousands of tonnes of sediment constantly swirl up and down the river. The sand banks move about and much of the sediment is always in suspension. If we build a barrage, thousands of tonnes of sediment will settle—somewhere; the difficulty is knowing where. If they settle in front of the generating turbines, the problems will obviously be acute; if they settle in the sea lanes near the locks, then huge dredging costs will have to be paid, and, in my view, they should fall squarely on the barrage company. The Port of Bristol is the port in this area that I know best and it has done exceptionally well over the past few years. Of course, other ports are affected on both sides of the estuary and they are at risk, too. They are all most concerned that the locks should be large enough and sufficiently well managed. In my view, the costs of building and operating the locks should be a charge on the barrage and not an additional overhead for the ports. Anything else would be unfair and damaging in terms of both commerce and unemployment. When the Oldbury power station was built a few miles upstream from the older bridge, a tidal reservoir over a mile long and half a mile wide was constructed to hold the cooling water when the tide goes out. I was told that, after elaborate tests, it was carefully designed to be self-scouring. In fact, it is no such thing, and it has been necessary for a dredger to be there permanently since the power station opened many years ago. That shows the difficulty of forecasting what will happen to the sediment if a barrage is built. So far as the barrage is concerned, I am a cautious enthusiast. It is potentially one of the biggest and most exciting engineering challenges of the next few decades, and it would change the environment, including that of those who live in the great cities of Bristol and Cardiff and the other towns nearby. We must investigate the problems and, above all, we must decide as soon as we respectably can whether to go ahead with it or whether to proceed with one of the alternatives. Whether by barrage or in other ways, we must harness the massive power of these tides and currents. Industry needs a lead. The Government must get on with the studies and then decide—and the sooner the better. The new ministerial committee has been sitting for nearly three months and I hope that by the end of this debate we shall know what it has achieved so far.