Areas of England most at risk of "serious water stress", and the factors used to identify these areas, were unveiled today by the Environment Agency.
The work took into account long-term forecasts for water demand and population and assessed the water available in each water company area.
There is a limited amount of water to be shared between people and the environment, and in some parts of England, because of population density, this amount is already stretched. Areas of England deemed "water stressed" are areas where with existing population or future growth, there will be more pressure on the finite amount of water available.
Under the proposed classification, 11 water company areas are identified as "serious" areas of water stress based on current and forecast growth in water demand, forecast population growth and current and forecast water resource availability.
Releasing a consultation document today, Identifying areas of water stress, Chief Executive Barbara Young said: "We've developed a way of determining which areas of England are the most vulnerable - where water abstraction is already close to or above acceptable limits, and along with a growing population and demand for water set to increase, pressures on water resources will multiply. Now we want individuals and organisations to tell us whether our approach is right.
"We expect climate change to reduce the availability of water resources because of longer drier summers. If we are to meet the long-term needs of society and the economy without overexploiting our environment, we need to understand how to target our water saving efforts and make better use of the water we have now.
"We need more action and we need to do things differently if we're to secure our water supplies for the future and minimise damage to the environment."
Barbara Young said water companies in stressed areas would need to adopt the highest level of water saving measures, including the possibility of compulsory metering, to manage water supplies well into the future and ensure the environment was protected. Elsewhere in England, the stress on water resources was lower but still significant. But it was important that water companies and their customers everywhere recognised the environmental consequences of the abstraction of water - and the energy used in pumping and treating it - by applying measures to make sure it was used efficiently.
Barbara Young said more metering and water efficient fittings and appliances could see substantial water savings in people's homes.
"There is a need for meters to be installed quickly in areas where water resources are stressed. In the south east we would like much of this to be achieved by 2015 - as long as social safeguards are in place to protect low income and vulnerable households," she said.
"The benefits of metering in reducing demand, energy and helping with more effective leakage management are unchallengeable."
Identifying areas of water stress was an action arising from the Water Saving Group, which was set up by Defra and involves representatives from the water industry and regulators.
Individuals and organisations are invited to comment on the proposals to classify areas of England according to their level of water stress. This coincides with Defra's announcement today of a consultation on extending opportunities for metering in areas of serious water stress.