Drier springs and parched summers are beginning to bite at water company reserves, and the inevitable price will be passed on through the meter. Business is turning to rainwater harvesting, which is both cheap to install and very effective
The fact that, on average, the UK is getting wetter year by year doesn't mean that our water supply situation is getting any better.

The problem has been extremes – periods when rainfall was so rapid that run-off from the land has mitigated against a steady rise in the water table, while reservoirs filled by the end of the year have faced extended periods of draw-off.Add to that increasing demand from housing and industry and, in the east especially, the possibility of reduced supply such as hosepipe bans is becoming a reality.
But the truth is that we waste far too much water. Water mains still leak more treated water than is healthy, and consumers – especially on unmetred supply – pour a third of it down the plughole unused. What's worse, we don't differentiate between treated water and untreated.
In its most basic form, rainwater harvesting is a water butt, used for centuries by gardeners to water their plants. There's no reason why business can't install a system purely to keep the office gardens green and leafy. But the big gains come when the water collected is pumped into buildings and used to replace some of the existing mains water systems via a header tank.
Flushing the loo or washing vehicles doesn't require drinking water quality. Yet this is the water we use to rinse away our dirt. Business now pays for every drop to be treated to standards much of the Third World would envy, only to sluice it down the drain. If it was the colour of money, we'd be more careful.
The water use landscape is, though, changing rapidly. Businesses with high water use are rapidly catching on to the potential for rainwater harvesting, which is neither expensive nor complex to achieve, and can both reduce the water bill and improve company image.
The potential water available is surprising. With annual rainfall in the UK at around 930mm, each square metre of roof could return the best part of a cubic metre of water a year. In real life, there's a level of wastage through loss and evaporation, but one scheme installed for a new-build housing project is expected to collect around 200,000 litres of rainwater from 240m2 of roof at a capital outlay of less than £3,500. Payback at local water supplier prices is expected within five years.
The Government's decision to add rainwater harvesting equipment to the Enhanced Capital Allowance scheme has further improved payback. In the example of a company spending £20,000 on equipment, it can reduce the taxable profit it pays tax on by the full amount, resulting in a net tax gain of around £6,000 – a 30% discount on the system.
Business and developers are cottoning on to the wisdom of such investments. The market grew 75% from 2006 to 2007, says the UK Rainwater Harvesting Association to a total £8 million. It would be a surprise if it didn't achieve the same by the end of 2008, despite the credit crunch.

FACT FILE

UK average annual rainfall allows the recovery of almost 900 litres of water per square metre of roof
Rainwater harvesting can reduce domestic water use by 50%, much more for some commercial premises
Collecting rainwater can reduce flooding events
Uses for rainwater include toilet flushing, commercial washing (vehicles, etc), and irrigation
Rainwater can be filtered and purified for other purposes