Scotland’s nature conservation agency last week painted an apocalyptic vision of a country devastated by the climate crisis, from polluted rivers to eroded peatlands and forests devoid of birds. Now comes a warning about another part of Scottish culture which could, it is feared, also be hit by global heating: whisky.

Scottish distilleries have revealed that during last year’s blistering heatwave, they had to halt production because they ran out of water. In a summer marked by high temperatures and little rainfall, water levels in springs and rivers fell so low that in the Scottish Highlands some whisky makers missed up to a month’s production.

“We lost the whole of September,” said Callum Fraser of the family-run Glenfarclas distillery on the River Spey. While some whisky makers take their water from the river, Glenfarclas – which means “valley of the green grass” – has its own private water supply. “It’s a natural spring, and it was dry,” said Fraser.

The month’s pause saw Glenfarclas production down by up to 300,000 litres, he added. Rumours abound of other distilleries seeing similar problems. “We weren’t the only one, just the most vocal,” he added.

The prolonged heat and longer dry spell meant even Scotland – known for soggy and temperate summers – had to cope with drought. Grasses stopped growing, which meant the Highland Games had to be cancelled, and wildfires spread in places they’d never previously been seen.

Experts fear that last year’s conditions may not be unusual in future. This week the environment agency is hosting a “drought summit” in London with water company bosses, as fears grow over similar temperatures this summer. Research has shown that last summer’s heatwave was made about 30 times more likely by the human-caused climate emergency. Some estimate that such heatwaves could be happening every other year by 2050 if emissions continue to increase.

Helen Gavin, who researches climate breakdown and drought at the University of Oxford’s Environmental Change Institute, said such extreme events place stress on the environment and the economy. “There’s an impact already,” she said. “It’s not just hot and dry summers, but strange weather like we’ve just had – 18C in February, that’s just weird. And that messes up biological and agricultural cycles.”

This has a cascading effect, Gavin added, which first affects crop yields, then the cost of production and thus the price paid by consumers. “And it means if we take more water from the environment to try and save whisky, a farmer’s crop, or so we can still turn on the taps, it comes at a huge cost.”

At some points last summer the Spey was running 97% lower than its normal minimum, and this winter has not brought enough rain to replenish it. “The water table hasn’t recovered yet, so it’ll be this year we see the full effect,” said Fraser. “We’ve still not had real rain yet.”

Further south near Pitlochry, the Edradour distillery lost a few days’ production last year for lack of water. Its owner, Andrew Symington, said the neighbouring river runs visibly lower each year. Edradour now plans to install costly cooling towers to mitigate the effect of lack of water in the future.

Drinks conglomerate Diageo, which owns several Scottish distilleries, would not comment on individual production schedules but said it had had “no major issue” because mitigation measures had already been put in place. Pernod Ricard, which also owns several distilleries, did not respond to a request for comment.