LONDON, Oct. 19 -- Where drinking water and river protection collide in four drought-hit parts of southern England, the government has now put in writing which comes first. Emma Hardy, the water minister, directed the Environment Agency to give "priority to protecting public water supply" in zones around the Wimbleball, Ardingly, Roadford and Colliford reservoirs, according to a direction published on GOV.UK on Monday.

The direction was made on Thursday, the day Defra declared severe drought in parts of Cornwall, Devon, Dorset, Somerset, East Sussex and West Sussex and announced the instruction in a press release. That release said the aim was to let water companies "keep more water in depleted reservoirs." It did not name the tool the l...