Guernsey Water operations manager Jon Holt said that amount was something he had not seen before.
‘It was unusual, because we had four days in a row of greater than 15 million litres a day water usage. Normally we’d expect to see that maybe once or twice over the summer for a single day, and that’s against an average of about 13.5m litres a day.’
Last Thursday was officially the hottest day ever recorded in Guernsey, with temperatures reaching a high of 36.4C.
With climate scientists predicting that heatwaves are likely to happen more frequently in future, resulting in a corresponding increase in demand for water, Guernsey Water said that its efforts to future-proof the island’s supply had never been more important.
That is why it pushed for the States to agree last year to turn Les Vardes quarry into a reservoir.
‘With Les Vardes in the long term, and then also the refurbishment of our water treatment works, we’re planning for those sorts of conditions,’ said Mr Holt.
‘Les Vardes will give us much greater resilience to longer term droughts.
‘What we find at the moment is, if we’re full, as we often are in late winter, say January, then when it rains we have to let that water go to waste.’
He explained that Guernsey Water holds two different types of water – raw and treated. It is the treated water, which is mostly held at Forest Road, which was impacted by the recent heatwave, while the raw water was unaffected.
‘Currently we’re in a healthy position, both in terms of raw water and treated water,’ he said.
‘But if that very high demand over a short period is sustained regularly throughout the whole summer, then we’ll start to see the impact on the water storage.’
But Mr Holt said it would have to be a very long, sustained period of hot weather for any restrictions, such as a hose pipe ban, to become necessary.
That has so far never happened in the 15 years he has been at Guernsey Water.
But he said islanders should still be careful about wasting water, and maintained the advice which Guernsey Water has had in its arsenal for 50 years since the memorable summer of 1976 – ‘every drop counts’.
‘If all of our customers can do small things, then it does make a big difference to the island overall.’
Although Guernsey’s water levels are currently healthy, not all of the water currently stored is actually usable because some of the smaller quarries do not have pumps, and Mr Holt said decisions have to be taken whether they are cost-effective to run.
‘We do have some very small quarries where we have to maintain infrastructure for ultimately what are fairly small storage volumes,’ he said.
The UK and Jersey Met Offices are forecasting a return to heatwave conditions from the weekend onwards, though temperatures are not expected to reach the record highs seen in the islands last week.
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