Farmers have been banned from taking water from the River Eden in Fife after it fell to a “critical” level, the second-lowest ever recorded.
The Scottish Environment Protection Agency (SEPA) said the majority of water abstraction licences would be suspended from midnight on Saturday.
A significant scarcity warning was also issued for the River Tweed in the Borders – where a ban could follow.
The National Farmers Union said it was “devastating” for vegetable growers.
Sepa said the suspensions would be lifted as soon as possible.
David Harley, Sepa’s chief officer circular economy, said: “Having to impose suspensions on water abstractions underlines the severity of the conditions being experienced in the east of Scotland this summer.
“It is not a step we take lightly, but the evidence is clear, and it is one we can no longer avoid.”
Abstraction is the process of taking water from a river, loch or other natural source.
Sepa said the main stem of the River Eden had only been lower in 1989.
Flows in Kemback in Fife have not been as low for this long since 2003 and Strathmiglo is also experiencing its most prolonged low flow period on record.
