The River Wye is now 2cm deep along a stretch in Hereford amid a heatwave warning, Environment Agency data shows.
สล็อต วอเลท brings together many other popular slot games into one of our web sites so that you can choose the game with the most complete login convenience.
Monitoring equipment at Hereford Bridge showed water levels had fallen to 2cm (0.8in), well below the top of the river's normal range of 3.3m (10.8ft).
Charles Watson, from campaign group River Action, said the UK's rivers faced an "ecological emergency" if the government did not act urgently.
Water temperatures have already reached 22C (71.6F), an expert said.
Retired Environment Agency manager and Herefordshire river expert Dave Throup added the water temperatures were expected to rise further in coming days.
During last month's heatwave, Natural Resources Wales opened the Caban Coch reservoir to increase the Wye's levels to save the river's salmon population.
"You can do that once," Mr Watson said. "You can't do that every time there's a drought."
Many fish were found dead in the Wye in July due to hot weather dissolving oxygen levels in the water.
Anglers have now been asked to to stop fishing for salmon and trout until temperatures have dropped sufficiently, a spokesperson for the Environment Agency said.