Although it has been many years since water restrictions were imposed locally, the utility has updated its Water Resources and Drought Management Plan to look at what the situation might be like in more than 50 years’ time, up to 2080, taking into account anticipated changes in weather patterns and population.
Europe is anticipated to experience wetter winters but hotter, drier, summers. With the island’s population also likely to grow, it is likely that this will add to the current supply deficit.
Guernsey Water said that the island had limited storage capacity, and in the event of a severe drought, there might be a need for rationing. Even putting every home on a water meter and collecting from more streams would not be enough.
Guernsey’s largest water storage site at the moment is Longue Hougue, with a capacity of about 1,165m. litres, followed by St Saviour’s Reservoir, which can store up to 1,039m. litres.
Once it is in use, Les Vardes is expected to be able to take about 1,945m. litres of water. However, it would not be filled until the middle of the next decade, at least, with the need for technical surveys, design, planning and an environmental impact assessment all needed beforehand. It is also estimated that it will take up to seven years to install the pipes necessary to connect the quarry to the existing water network.
‘UK winters are projected to be up to 30% wetter by 2070, but summers up to 60% drier depending on the region,’ said Guernsey Water managing director Steve Langlois.
‘A dry summer is fine if we have had a wet winter beforehand, but in some years this will be followed by a dry winter and a second year of drought, like there was in 1991 and 1992, except in the future a more extreme drought than this is expected to become more likely.’
The best way to avoid the need for restrictions will be to increase the amount of water in storage before a two/three year drought begins, he said.
Adding Les Vardes will increase the total water storage in the island by 45%, and that could mean that some former quarries will no longer be needed as reservoirs. As well as approving the quarry for water storage, the States has also decided that Black Rock would become a storage site for inert waste.
Previously, the Longue Hougue quarry had been suggested for inert waste disposal, but as well as being very deep and having steep sides, which would make access to the bottom difficult, Guernsey Water said it stores water from the island’s largest water collection station and provides about a quarter of the raw water storage which is used to supply large areas of the island daily.
Concerns over low water levels after ‘exceptionally dry’ spring
Guernsey Water is concerned about the island’s reserves over the summer.
Last week it collected 85m. litres and islanders used 84m. litres.
But current storage levels are at 91.5% and, after a very wet January, the utility has said that spring has been ‘exceptionally dry’, with March rainfall 84% down on the monthly average and April down 29%.
‘Our storage levels are 3% below where we are comfortable with. That might not sound like a lot, but it’s actually 120m. litres – or 10 days’ supply,’ said a spokesman.
‘We do expect demand to outstrip supply in the summer, that’s not unusual. But the reduced rainfall means we’re going into peak demand months with less in the tank, and that is unusual.’
Guernsey Water is now intending to publish supply and demand figures and overall storage levels on a weekly basis.
It said that people’s actions would make a difference to future storage levels.
‘We’re doing everything we can to ensure as much water as possible gets into our 14 reservoirs and we need you to do everything you can to use water as wisely as possible,’ the spokesman added.
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