A hosepipe ban is being introduced for about one million customers across Hampshire and the Isle of Wight for a second year in a row.

Southern Water said the restriction would come into force on 10 July but is requesting customers to “put down their hosepipes now, to avoid putting the network under further pressure”.

A ban for South East Water customers in Kent started from Friday. Southern Water said its restrictions would likely run until the autumn unless there was significant and sustained rainfall.

It comes after the warmest spring on record and last week’s record-breaking heatwave.

It is the first time the company has introduced a temporary use restriction in consecutive years, following on from last year’s ban from mid-July until the end of October.

The company said the River Test, which supplies most of the water to homes and businesses in Hampshire and the Isle of Wight, was at a “critically low level”.

“In June, we’ve actually seen a third of the flow and so the models have just not necessarily predicted that,” said Tania Flasck, director of water operations.

“When we’ve actually measured the levels we’ve seen it’s dropped down a lot, a lot further and faster than we’ve anticipated.”

Households are being asked to use watering cans or buckets for activities such as watering gardens, filling paddling pools or washing cars.

Southern Water said investment in infrastructure, including the UK’s first new reservoir for 30 years, would help stop it taking water from the Test and Itchen rivers by 2040.

Paul Vignaux, executive director of the Test and Itchen Association, said: “…we have no reservoirs here and all the water comes from the river or from the aquifer.

“And effectively, if you take water from our rivers and aquifers, you’re taking water from nature.”

He added: “When the flow gets slow the temperature rises and pollution gets concentrated.

“Fish are finding it difficult to navigate up and down the rivers and so they are hiding in ever shrinking bits of river where they can keep their temperature down.”

Southern Water has claimed it achieved a record year of leakage reduction, equating to 27 million litres per day, and has found and fixed 2,840 leaks since January.

But more was needed to help protect internationally important chalk streams, it added.

The company said a hosepipe uses 1,000 litres of water an hour, which equates to “one person’s weekly water use in just 60 minutes”.

Exemptions include those on the Priority Services Register and WaterSure customers with mobility or health needs.