‘We’re hoping and expecting the rain to come’

As I sat in Jon Holt’s office last week, having been invited along to hear about ‘how things have gone over this summer and why we really need it to rain ahead of 2027’, I was somewhat taken aback to be told that since March, there had only been one single solitary week during which Guernsey Water had been able to collect more water than it supplied to us, its customers. One week, in other words, in which storage went up.

Well, this was the public utility spokesman’s version of the commentator’s curse.

At the beginning of last week Guernsey had received 89% of the rainfall you would normally expect us to get by that time of year. A week later, that figure had risen to 98%, after three inches of rain in six days. In the last week, 182 million litres were collected, 82 million supplied and therefore 100 million added to storage. You could fill Beau Sejour swimming pool 200 times with that.

Yet despite this heaven-sent liquid bounty, overall storage levels are still only at a rather modest 71%, which is about the same as this time last year and 8% below the 10-year average.

Jon knows this latest deluge is on the way as we speak, as he is by his own admission, ‘fairly weather obsessive’. But he lays out the state of play regardless, keen to convey to all of us owners of taps that there’s never room for complacency in drought management planning.

‘We’re at the end of the summer draw-down and we’re at the start of where we’d expect to see resources pick up and storage levels to start increasing,’ Jon tells me, ‘so we’re hoping and expecting the rain to come.’

He explained that all the scheduled maintenance had been carried out at the collection stations in anticipation of precipitation.

‘The change in rainfall is noticeable,’ he says.

‘In the summer, we get very high intensity, low duration rain and now we expect to see more long-term rain which replenishes our reserves. It’s the day-after-day-after day of steady rainfall which makes a difference to the levels of stored water.’

So there you have it – when Guernsey Water staff are looking out of the windows of their St Andrew’s headquarters, they’re not happy unless it’s miserable.

Having said that, there is, ironically, a frustrating scenario that kicks in when – as happened in February – the storage reaches full capacity.

‘Last winter, we were full by January, so everything that fell in late January and during a very wet February couldn’t be collected – we had to let that go out to sea,’ says Jon.

Bringing Les Vardes Quarry into play as the latest addition to Guernsey Water’s raw water storage facilities will boost capacity by anywhere between 30 and 45%, making this situation more rare. However, Jon tells me he doesn’t anticipate Les Vardes being up and running any sooner than about 2040.

‘It’s a long way off,’ he says. ‘We need to do a lot of planning before we’re anywhere near piecing that together, looking at investment, technical solutions and the onsite practicalities of laying transfer mains.’

In the meantime, it’s a case of crossing fingers that we don’t get two consecutive dry winters with a hot summer in between.

‘Our consistent advice, in any situation, is to be ‘waterwise’,’ says Jon. ‘Water is a finite resource, so we encourage water efficiency. No-one’s watering their lawns at this time of year but keeping streams clear is important. Any blockages cause flooding and we lose the ability to collect that water.’

A typical place for a blockage, he says, is at the head of a culvert, where streams, douits and drainage are diverted below roads. Vegetation can easily get washed downstream, blocking the head of the pipe. So the sort of blanket debris we saw after Storm Austen is certainly best cleaned up sooner rather than later if water wastage is to be avoided.

When water levels drop in the island’s reservoirs, Guernsey Water then has to go to the expense of pumping it around from one reservoir to the other, and has to spend more on the chemicals needed to treat it, according to water quality risk manager Daffyd Griffiths.

‘As our water levels are going down, we’re not able to be as selective as ideally we would like to be,’ he says.

‘If water was plentiful, we would be collecting from only the best quality sources, and doing the minimum amount of treatment and we would spend less money on chemicals to treat that water to the same high standard. When we’re in a prolonged drought scenario, we don’t have the same option not to collect something.’

A big consideration is PFAS – that’s the chemical found in firefighting foam that has previously contaminated certain areas of soil around the upper parishes.

‘What we have found with PFAS is that it is present everywhere to a certain extent,’ says Daffyd, ‘so we’re able to deal with it in low to medium concentrations but in some sources it’s off the charts and we don’t want to be using those.’

Thus, two streams that previously flowed into St Saviour’s Reservoir have been diverted away. Walkers on the Millennium Walk, when it’s open, can see the infrastructure required to divert. Water from the Petit Bot stream is also not collected.

Contrastingly, two other streams that flow into St Saviour’s Reservoir are the cleanest on the island, from a PFAS point of view. But it’s not just PFAS that causes headaches.

‘We did have quite a serious pesticide contamination incident at the Longue Hougue reservoir in the spring of last year, with metamitron giving a reading quite a way above the drinking water standards, which impacted quite severely how we were able to use that reservoir,’ says Daffyd.

Guernsey Water can pump water around between storage facilities in order to water down problem areas and bring the numbers back down to acceptable levels, but lower water levels generally means fewer options. And this also means more frequent sampling.

‘We do something called risk-based sampling, so essentially our default level is once a month for something like a pesticide sweep but then as we detect things, we increase the monitoring,’ Daffyd says.

‘We’ve found that’s been really effective to mean that we can catch it early enough so that we notice it before it becomes a significant issue but we’re not spending money in excess of what we need to, because it all adds up.’

Guernsey Water also seeks to save on its budget by moving water around just to keep the water going into the treatment works at a consistent level of quality.

‘Chemical dosing and flow rates depend on a certain make up of the water,’ says Jon, ‘so if we change the source of water from St Andrew’s Quarry to St Saviour’s Reservoir, that will affect the water treatment process and we’ll have to make adjustments.’

So rather than dumping all the water from St Andrew’s into St Saviour’s in one go, it has been pumped up there gradually over the last few months, which is why St Saviour’s has been looking fairly full even during those months of little rain, while St Andrew’s has shrunk to little more than half of its capacity. This is done deliberately, ahead of the wetter months, because the streams that flow into St Andrew’s can be relied upon to fill it up quickly with good quality water.