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The outlook is cloudy: is this year's drought a one-off or the shape of things to come? Projections of the effects of climate change on water show a lot of uncertainty.

With drought orders in place across half of England, it's perhaps hard to appreciate that the long-term risk to the UK in terms of water supply could be not a shortage at all but possibly even an over-abundance. Though, as ever with statements based on weather forecasts, there's a degree of uncertainty.

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More than that, in fact. Long-term projections for climate change in the UK for the rest of the 21st century and a bit beyond suggest on balance that it's going to be a wetter place--rainier winters, perhaps sunnier summers, though some predictions don't rule out wetter all year round.

But it may be the wrong kind of rain. Water management--abstracting from rivers and collecting in reservoirs and in underground aquifers--is about steady accumulation, whereas one effect of climate change might be to make the UK's weather more irascible: storms and tempests tend to lead to flooding without necessarily benefiting long-term water conservation. And the preponderance of evidence at present suggests shortages rather than too much water are the more likely.

Water is in fact one of the big subcategories in the government's Climate Change Risk Assessment report, published earlier this year by the Department for the Environment, Food and Rural Affairs (Defra). Water is big and strategic because it affects virtually everything else; but in terms of the background documentation to the report, water merits a sector report of its own, a large document prepared by the hydrology specialists at HR Wallingford for Defra and based on years of their own and other people's research.

The documents are very much a preliminary attempt to identify the areas where there are the greatest risks, and the intention is that they will be updated to take account of developing knowledge.

Even at this stage, though, the view is complicated, and not just by the unknowns of climate change. "Although we anticipated that floods, droughts and heat waves would feature prominently, we also found that the overall risk landscape was complex and affected by geography, social and economic change, the connection between risks and the international context," said Dr Steven Wade, FIR Wallingford's water management group chief.

There's no surprise that the areas where there is seen to be greatest pressure on water resources across the rest of this century and into the next are in the south-east of England and the Midlands.

Projections of changes in river flows in summer across the UK as a whole in the 2050s range from an average of -35% in the Anglian region to -15% in wet bits of northern Scotland. Wetter winters may help a bit, but cannot compensate overall.

This is not helped by other factors. Population growth is projected to be highest in precisely the regions under greatest pressure from water shortages. This doesn't just increase demand on water supplies: it can also create other pressures through increased urban run-off and potentially more pollution. Availability is what we all think of as the main water problem when we have drought orders, as at present; some of the risks from climate change identified in the report to Defra have impact on water quality at least as much as water quantity, though data in this area is less well developed.

HR Wallingford in fact identified more than 50 different risks in the water sector, though it selected just 10 of them for further research and analysis. Most aren't really susceptible to quick summary, as they're hedged around with the uncertainties over climate and emissions, but the panel on this page contains a single sentence on each.

In all cases, the work done so far largely serves to indicate that there is a lot more work still to do. Whether this year's drought is a relevant factor in the longer-term scientific investigation is unclear; it may, however, have the benefit of kick-starting the discussion and getting across the point that water is a strategic necessity. ^

RELATED ARTICLE: Ten risks in the water sector

* Aridity is likely to increase unless weather is wetter than the mid-range projections.

* Low river flows are likely to become more commonplace.

* The amount of "deployable" water is likely to be less.

* Climate change could increase water demand (though not by as much as population growth).

* Deficits are likely in the balance between water supply and demand, with severe regional variations.

* Increasing numbers of people will be affected by these deficits between supply and demand.

* Lower river flows affect the ability of sites to meet environmental standards.

* Water abstraction by agriculture, industry and utilities would be unsustainable in more locations.

* Pollution increases, particularly in rivers.

* There is a likely increased frequency of overspills from storm sewers.
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Title Annotation:Utilities
Publication:Environmental Engineering
Geographic Code:4EUUK
Date:Apr 1, 2012
Words:777
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