I am always nervous about the beguiling argument that we should use demand management to improve the efficiency of current water use as an alternative to building new storage facilities (NCE last week).
The perception that water is 'lost' or used inefficiently is unwelcome both to the public and the politicians. But is water really lost and does water behave in the same way as energy does?
During droughts we are urged to use water carefully with such comments as 'turning off the tap while you are brushing your teeth will save 40 gallons of water each week'.
But does it? It is argued that turning off the tap leaves 40 more gallons in the distribution system for use elsewhere. But the water that was previously 'wasted' went down the drain and if this was captured and used again by someone else then wastage was not lost to the system but was still used effectively.
The concept of water use efficiency at the domestic level of individual users has little meaning. When water is in short supply it is important to make sure that all water that is 'used' is put back into the system and is used as many times as possible before it is finally 'lost' to the sea.
Demand management does have a significant role to play in finding ways of improving the effectiveness of existing water resources by reducing real losses and increasing the productivity of water. But we may well be over-estimating what it can do for us.
Melvyn Kay, Research, Training & Consultancy Services, 5 Lea Road, Ampthill, Bedford MK45 2PR