Why a national grid won't work

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More than 200,000 billion litres of rain fall on the British Isles every year - more than enough to supply everyone's demands. The problem is that most of it falls during the winter, while our demands for water continue and increase during the summer.

Since the great drought of 1976, the idea of a national water grid has been debated many times. The analogy is with the electricity grid: a network of pipes that would cover the whole country and carry water from areas that have it in abundance to those where there is a shortage.

The water grid was considered most recently by the National Rivers Authority in March 1992, when it was suggested that Britain's network of canals could act as water transfer channels. By last year, however, when the NRA published its assessment, Water: Nature's Precious Resource, the idea had fallen victim to straightforward economics. To supply 100 million litres of water a day through a national grid system would take pounds 400m to pounds 600m in development costs. By contrast, a reservoir supplying the same amount would cost pounds 50m to pounds 250m to build.

Thus, instead of the electricity industry, a better analogy might be farming: make hay in the summer for consumption in the winter. If the demand for hay grows over the years, the farmer has to build bigger barns. The water industry believes that increases in the future demand for water will eventually force it to increase storage capacity for its harvest of the winter rainfall. And this means that if we insist on watering our gardens in a drought, we will see the cost in terms of more reservoirs in our countryside.

Tom Wilkie