Water, we are told, is the new oil. It is the likely cause of future wars and the potential target of future terrorist outrages. From the Jordan to the Tigris, the Mekong to the Zambezi and the Nile to the Rio Grande, the water in international rivers excites dispute. Even underground water inflames passions when one nation drains reserves that leave wells the other side of the border running dry.
I have half-a-dozen recent books with the title Water Wars - it alliterates so handily. But there is also a growing library of books that argue the contrary -that water is rarely the cause of conflict, merely an excuse to revive ancient animosities. And that nations normally have more reason to cooperate over water resources than to fight over them. Rivers are not, proceeds this argument, like land or the oil beneath it. Their waters flow; even a dam can hold them only for a while.
Part of this difference of view is down to authorship. The water wars books are usually written by journalists, political lobbyists or laymen. Maybe they are alarmists and scandal seekers. The books that are sceptical about water wars are usually by professionals. But that does not necessarily make them right. These authors are often advisers to protagonists in water disputes. They may know their subject but they prefer to be seen as problem solvers not warmongers.
Jack Kalpakian, a Moroccan academic, is firmly in the sceptics' camp. He says wars are about national identity, not water. And this study of three highly pertinent cases - the rivers Nile and Indus, and the twinned Tigris and Euphrates - makes a compelling if hardly watertight case.
The way he tells it, about the only thing India and Pakistan have not been to war about is water. Thanks to the US-brokered Indus Waters Treaty signed in 1960, they share the river's water. There have been rumblings, but nothing worse.
As Kalpakian shows, Pakistan has got a good deal. It is hugely dependent on a river little of whose waters arise on Pakistani land. Afghanistan and India contribute more but take far less. But this optimism may be premature. Pakistan also uses its share of water with spectacular inefficiency, and the river often fails to reach the sea. A run of low-flow years could trigger a major crisis in the downstream province of Sind.
Pessimists may say the only question is whether a water war will be between Sind and upstream Punjab, or between Pakistan and India.
The disputes over the Nile are quintessentially a British creation. At a time when our writ ran most of the way along the world's longest river, Britain gave most of the Nile's flow to Egypt, the rest to Sudan and none to upstream nations such as Ethiopia, which contributes three-quarters of its flow. Egypt continues to take the lion's share and threatens war against any neighbour who questions this.
But the symbol of Egypt's control of the river, the giant Aswan High dam, undermines its claim. It is a vast drain on the river's resources. Up to 15km3 of water a year evaporate from the surface of its huge lake. In a dry year this can be more than a fifth of total flow. If Egypt could reach agreement with its upstream neighbours for them to store water behind dams in the cooler, cloudier highlands, the majority of that wasted water could be saved to irrigate crops. But Egypt will not budge. Even without declarations of war, fear of its neighbours has created a huge hydrological inefficiency that may one day lead to conflict.
Kalpakian provides a long and interesting description of the disputes over the Tigris and Euphrates, in which Turkey is finally attempting to capture its "share" of the waters of the two rivers, which get most of their flow within its borders. But his concern with identity and water conflicts seems to stop with nationality. There is hardly a mention of how a combination of Turkey's water captures and Saddam Hussein's notorious drainage projects have emptied Iraq's huge Mesopotamian marshes and forced into exile their inhabitants for five millennia, the Marsh Arabs.
The conflict between Saddam and the marsh inhabitants was assuredly about identity. But you would get a dusty reception among marsh refugees today if you suggested they were not the victim of a water war visited on them in the 1990s by Saddam.
Water for Life , by contrast, is a concise and erudite primer aimed at helping hydrologists and environmental managers to find a common language to talk about policymaking for rivers, lakes, wetlands and underground water reserves. Its propensity for checklists and tables hardly makes it a layman's read. Its poor index is a shame. And its canvas only fitfully extends beyond the hydrology of the US.
But it is up to date, with plenty of discussion of water politics since the World Commission on Dams reported in 2000. As befits its distinguished authors, it exudes authority. And it has an valuable 35-page listing of website sources that, for this reader at least, is the most valuable thing in it.
Fred Pearce is environment consultant, New Scientist .
Identity, Conflict and Cooperation in International River Systems
Author - Jack Kalpakian
Publisher - Ashgate
Pages - 222
Price - £47.50
ISBN - 0 7546 3338 1