Water companies across southern and eastern England are to introduce hosepipe bans amid drought conditions.
Seven firms say they will impose water restrictions after two unusually dry winters left reservoirs, aquifers and rivers below normal levels.
Southern Water, South East Water, Thames Water, Anglian Water, Sutton and East Surrey, Veolia Central and Veolia South East are to enforce restrictions.
Five of the companies said they will impose bans from 5 April.
Sutton and East Surrey, along with Anglian Water, are yet to confirm when the ban will come into force.
The drought-affected areas are the south-east of England and East Anglia.
But the Environment Agency warns in a new report that the drought could spread as far north as East Yorkshire and as far west as the Hampshire-Wiltshire border, if the dry weather continues this spring.
In its report, the Environment Agency warns that drought conditions are expected to spread across more of England in coming weeks, unless strong rains arrive.
It will also warn of effects on agriculture that could raise prices of potatoes and other vegetables.
Environment Secretary Caroline Spelman said the temporary restrictions would "help protect the public's water supply in the areas most affected by the record low levels of rainfall we have experienced over the last 17 months".
She said: "We can all help reduce the effects of drought by respecting these restrictions and being smarter about how we use water.
"Taking action now to reduce how much water we use will help us all in the future."
A number of water companies in the southern half of England, covering about 20 million people, are understood to have contingency plans in place that could lead to bans on non-essential uses, perhaps before the end of March.
These could include bans on car-washing, watering gardens and filling swimming pools.
Meanwhile, the area formally in drought is expected to extend beyond south-eastern counties to include parts of Yorkshire.
Counties that have received much less rainfall in recent months also include Shropshire and Somerset.
The National Farmers Union has warned of the impact on both arable and livestock farming, and is asking for restrictions on agricultural water use to be avoided wherever possible.