Thames Water’s call to action, backed by the Angling Trust, comes after an exceptionally dry two years in London and the Thames Valley. Since records began in 1884, only 1892-3 and 1920-1 have seen less rainfall.

Levels in many of the rivers feeding the Thames have fallen to shockingly low levels. Flows in the River Lee, running from Hertfordshire into northeast London, are just 24% of their long-term average, while those in the Kennet in Wiltshire are running at just 33%, having dried up completely west of Marlborough.

The company is asking its 8.8m customers across London and the Thames Valley to make the link between the local river or groundwater source where their water comes from, and to consider how reducing their usage can have a positive impact.

Posters urging people to order water-saving gadgets went up today in seven communities across the Thames Water region encouraging people to order free water-saving gadgets – including shower heads, tap aerators and shower timers – from the company’s website, www.thameswater.co.uk/waterwisely, or by calling 0800 358 6665.

No longer if - but when 

Richard Aylard, sustainability director for Thames Water, said:

“We all need to recognise that the water coming out of our taps comes from our local river or from the aquifer that feeds that river - and the less water we all use the less we need to take from the river.

"Our region, covering the Thames Valley and London, has received below-average rainfall for 18 of the past 23 months, with 2010/11 the third driest two-year period since records began 128 years ago, and many of our rivers are running low as a result.

"It is no longer a case of if we have a drought this year but rather when, and how bad. This is not just our problem, it’s everyone’s problem and we can all do our bit to help - for example, turning off taps while we brush our teeth can save six litres of water a minute.”

As well as reducing the amount of water flowing off the land into rivers, the recent lack of rain has caused the groundwater – the underground water table, which drives flows in rivers all year round - to drop significantly, in some areas to below the levels recorded before the 1976 drought.

Majority of people unaware of crippling drought

Mark Lloyd, chief executive of the Angling Trust, said:

"The vast majority of people are unaware that we are in the middle of a crippling drought. River levels are lower in many areas than they were in 1976 and many rivers in the South East have dried up completely. Rivers and wetlands are without doubt the most important wildlife areas left in Britain and water levels are vital to support many species that rely on them.

"Angling, one of the nation’s favourite pastimes and an important economic driver, has become impossible in many areas or clubs have closed their waters to protect the fish.

"We’ve endured months of below average rainfall, but there is little evidence that anyone is doing anything to change their water use as a result. We all need to think about the water we use every day and to take action to cut out waste now.

"Many modern city residents have become completely detached from the fact that the water that comes out of their power shower, or the hose that washes their car, is water that should be keeping a river flowing or a wetland wet. People waste vast amounts of water because they don’t pay for it themselves, but there is a huge cost for the community and the environment from their thoughtlessness."

Across London and the Thames Valley the company takes 70% of the 2.6bn litres a day of water it supplies from rivers, and 30% from underground boreholes. However, in the Thames Valley, 70% of people’s water comes from groundwater and 30% from rivers.