China has a damming programme for six of the world's great rivers that rise in Tibet - the Indus, Sutlej, Mekong, Brahmaputra, Salween and Yangste - and feed by irrigation an estimated 1.3 billion people.
The Mekong whose flow takes in Yunnan province in China, Laos, Thailand, Cambodia and Vietnam and feeds an estimated 60 million people has been severely depleted in the last two years. Despite drought in Yunnan last year in the peninsula of southeast Asia, users downstream are turning their frustration on the Chinese government whose three dams on the Mekong since 1996, to generate hydro-electric power, are set to increase to twelve. On China's border with Burma, a giant hydro-electric dam, the Myitsone, is being constructed near the source of the Irrawaddy to supply power to Yunnan, affecting the Kachin people of north Burma who will be left to pick up the environmental tab.
Since it began damming the Yangtse in 1995, China has acquired a large appetite for hydroelectric power and a lack care for environmental consequences, although it may argue a vast saving to the carbon footprint estimated on large dams at 200m tonnes of carbon.
More worryingly in the last decade Beijing's engineers have turned their attention to Tibet, south Asia's water tower and rich mineral depository - copper, iron, lead and zinc desposits are estimated to have a value of £80bn/ $130bn - where the region's great rivers rise and whose flow downstream provides livelihood, irrigation and food to an estimated 1.3 billion people around and below the Himalayas.
Here the Indus, Sutlej, Mekong, Brahmaputra, Salween and Yangste emerge to start epic journeys through the subcontinent, southeast Asia and China. Little more than deep running mountain torrents, they catch the seasonal glacial melt and drop through immense heights - the vital pressure for momentum to drive them off the Himalayas and into the plains below - picking up thousands of small tributaries as they go.
For China, with glacial melt on the plateau rapidly increasing because of climate change, Tibet's rivers are proving as rich resources for hydro electric and geo-political power as its mineral wealth. But frenzied dam construction projected until 2020 means that a prehistoric irrigation system that dates back 30 to 40 million years is coming to an end. Delhi-based travel writer Alice Albinia noted in 2005 that the Chinese had built a dam on a tributary of the Indus at Senge Ali as she was in the last stages of her Indus journey. "The structure itself is complete, but the hydroelectric elements on the riverbed are still being installed. There are pools of water this side of the dam, but no flow. The Indus has been stopped," she writes. She suggests that the main force and volume of the river comes from its flow and tributaries in Tibet, Ladakh and Baltistan rather than from Punjab tributaries. Infact Pakistan's floods in summer 2010 were the result of the Kabul River's flow into the Indus and the deciding role was played by jet stream weather systems.
If river systems are complex, the speed of China's dam building is geopolitically contentious. Tashi Tsering, a Tibetan expert of environmental policy at the University of British Columbia, has been monitoring the construction of dams since 2004 with the use of Google Earth and official documents from Beijing.
He has shown how the Brahmaputra, Tibet's last main undammed river, was due to receive a 38 gigawatt hydropower plant - more than half as big again as the Three Gorges dam, with an energy capacity of half of the UK's national grid - within a series of 28 lesser dams for the river, including a 500MW hydroplant at Zangmu and a huge plant at the great bend of the river at Metog where the river falls 2000 metres on its journey to eastern India. He has also found completed dams on Tibet's international rivers including the Sutlej (a hydroelectric project at Langchen Khabab) and the Indus.
The geopolitical and environmental consequences of China having a hand on the water taps of Tibet are immense for the region south of the Himalayas - both the subcontinent and southeast Asia. Damming dramatically changes the character of water not only in terms of pressure and flow but in course as well. By rockblasting new channels the sluggish slipstream that emerges from the dam's base can be diverted.
Off the Tibetan plateau, the Brahmaputra which runs through Assam and on the border between India and Bangladesh is the first flashpoint of the water battle in south Asia, and not least because India's northeastern state of Arunachal Pradesh, the bridging state between Tibet and Assam, has long been claimed by China.
On the eastern subcontinental plains, farmers rely on glacial melt and high river pressure for irrigation between February and June. The water treaties signed in the region in the 1960s after the China-India war of 1962 are out of date and inadequate; India's tense geo-political relations with China and four disputed territories across the Himalayas have put India on the defensive. Delhi is alarmed that ultimately Beijing may intend to divert the river for Chinese farmers.
Within days of Wen Jiabao's visit to India in December 2010, the Indian press reported that intelligence agencies had found 24 new hydro electric projects on the Brahmaputra and its tributaries in Tibet, a four-fold increase. The course of the Brahmaputra, as well as China's provocative suggestion that Indian Kashmir is a 'disputed territor' were at the heart of Manmohan Singh's statement on Wen's visit that India had " some outstanding issues with them (the Chinese) which we hope to resolve in an atmosphere of friendship." Meanwhile the implications for Burma of Chinese interest in the Irrawaddy and south Asia's dependence on the Mekong are troubling.
If there is good news at all it comes from Pakistan, although under terrible circumstances last summer: that river flow and irrigation depends upon south Asia's monsoons and weather systems - the droughts in Russia and the Chinese and Pakistan floods were due to atmospheric pressure, governed by global warming, high up in the jet stream - as much as mountain river sources. Bangladesh's epidemic of land erosion through the Sunderbans delta might be eased with proper damming of the Brahmaputra if India (upstream) can take the initiative first.
Too much water, not enough water. The present century is predicated to be tinged with its geopolitics. Prior to the flooding in Pakistan, there was constant documentation over hundreds of miles of the Indus's reduction to a thin stagnant trickle and the incursion of sea water from the Arabian sea delta, and much of this has been blamed on damming in the north and the demand on shared waters with India.
The climatic events of summer 2010 demonstrated how terrestial diversion of water is secondary to what happens high up in the atmospheric weather systems as global warming combines with El Niño cycles.