BOOK REVIEW / Alter the courses of history - dam the consequences: 'The Dammed' - Fred Pearce: Bodley Head, 18 pounds

THE SUPERDAM is perhaps the supreme symbol of man's mastery over nature. One by one, free-flowing rivers across the world are being tamed by giant plugs of concrete whose bulk is expressed in multiples of the great pyramid of Gaza and whose height is measured in post office towers.

But, as Fred Pearce makes clear, the industrial might and gleaming modernity of the superdams are, with very few exceptions, a thin mask over the economics of the pork-barrel and the politics of the gun-barrel. And those rare exceptions, like the Hoover dam on the Colorado River, have inspired hundreds of spectacular failures. The billion-dollar Balbina dam in the Brazilian Amazon, for example, has drowned over two football fields of rainforest for each kilowatt it generates. And the Akosombo dam in Ghana expelled 80,000 people from their homes and brought bilharzia to even more - to give the Kaiser Corporation electricity at a twentieth of the world price in order to smelt foreign bauxite.

In this comprehensive and well-researched book, we are taken on a mind-boggling world tour of the incompetence, corruption, stupidity and sheer folly which has dominated half a century of dam building. The resulting disasters - human, economic and ecological - have been on a scale that is matched only by that of the dams themselves.

Pearce also places modern hydraulic engineering in historical perspective, tracing it back to the aqueducts that sucked hundreds of springs dry to supply water to the million inhabitants of imperial Rome, and beyond that to the irrigated fields of Mesopotamia of 5,000 years ago, long since reduced to desert through a build-up of salt, causing the collapse of the world's first civilisation.

But the news is not all bad. In refreshing contrast, we are told of ancient water technologies in tune with the fall of the rains and the flow of the rivers - many of which are still used today by supposedly primitive farmers. For example, in parts of the arid Middle East, sparse rainwater is harvested by stone walls and channelled on to shining green fields in the desert. The system has now been adapted by Oxfam to rehabilitate the eroded slopes of Burkina Faso, showing that this could be the way of the future as well as the past. But all too often the soft technologies are destroyed by hard modern developments, which variously steal, dry out, flood, waterlog or salt once productive land. The bigger and more expensive a project, it seems, the more it will take away from ordinary people, and from subsistence farmers in particular.

Looking ahead, we are left wondering whether grandiose plans - to dam China's Yangtze River, flooding out a million people; to divert the Zaire River to Lake Chad; to funnel the Yukon River down to southern California; to bring Canada's Arctic rivers south to the Great Lakes; and to channel Siberia's north-flowing rivers to the disappearing Aral Sea - are visions of a brave new future, or signs of the dam-builders' last mad delirium.