A water supplier has been granted a drought permit so it can continue to take water from a Hampshire river.
The Environment Agency said the water firm's current licence allowing it to take water from the river had been in place for 37 years.
There are only about 200 chalk streams in the world - most of them are in the southern half of England.
A chalk stream is broadly defined as one that gets most of its flow from chalk-fed groundwater.
The very pure water is rich in minerals and provides an ideal habitat for insects, fish, plants, crayfish, birds and mammals including water vole and otter.
Before it can use the permit Southern Water must first apply temporary use bans on customers' use of hosepipes and pressure washers to cut water use.
Mike O'Neill from the Environment Agency said: "Although river flows are just below normal for the time year without the drought permit there is a risk that the water company will not be able to maintain supplies.
"However in agreeing to change the abstraction limits we have been clear with the company that the environment must still be protected if they do need to take more water from the river."
The water from the river supplies homes in West Southampton, the New Forest and the Isle of Wight.
The Environment Agency has told the water firm that over the longer term it must secure another water source to help protect the chalk stream.
(Original post from https://www.bbc.co.uk/news )