Without question, China has the best portfolio of hydro electric sites anywhere. The multiple mountain valleys are supplied with ample rainfall coming out of Southeast Asia. It simply has the best natural design anywhere in the world and of course, China is using it. I did not however have any concept of the dimensions of their enterprise. They now have 26,000 dams.
The one environmental issue that I would like to see addressed better is provision for upstream migration. This has thwarted ready solution for decades, but last year a German engineering firm showed us a horizontal water wheel or turbine system that extracted power from a hydraulic head that was less than a meter. Obviously this is a high volume, low velocity system that is easily survivable for fish coming down river and easy to engineer a workable ladder for upstream migrators. The design lent itself to stacking in a silo like structure that could obviously see the fish up river past a dam.
I suspect that these rivers once had major salmon fisheries that were simply fished to extinction by the extreme populations on their migration routes. It would be quite straight forward to reestablish massive stocks and runs on these river systems. The long mountain rivers are ideal for spawning and possibly are superior or equal any in the world. The salmon may even control the carp for all I know (it would be nice to get feedback on that).
The reason I bring that up it that salmon runs are way to vulnerable to collapse, even with the use of primitive technology. It is way too easy to set a weir on every creek and grab all the spawning adults. I suggest that this happened where human populations grew sufficient.
China is in a position to impose proper fish management rules and then to successfully restock all the rivers of China. Building these fish ladder turbines allows migratory fish to access the mountain spawning grounds.
October 13, 2009
Damming the Yangtze: Are a Few Big Hydropower Projects Better Than a
Lot of Small Ones?
China is rushing to build dams along the upper reaches of the Yangtze River, in part to protect the Three Gorges Dam, but can such hydropower development be done better?
The proposed Xiaonanhai Dam would stand athwart the mighty Yangtze River some 30 kilometers upstream of the industrial metropolis of
The dam is just one of 19 proposed dams on the upper reaches of the Yangtze, upstream from the massive Three Gorges project near Yichang—and one of nearly 200 proposed dams on the Yangtze and its tributaries.
"Within 30 to 50 years, hydropower will be the main energy we should rely on," Lai Hun Suen, a professor of sustainable development at
That choice has consequences: At least 1.2 million people moved to
"There are 338 kinds of freshwater fish in the Yangtze River and 162 of them are endemic to the river—that is, found nowhere else," says ecologist David Dudgeon of the
The question is: Can hydropower in China be done more sustainably?
A drop in the bucket
Xiaonanhai would generate 1,760 megawatts of electricity—three quarters the yield of the
That's why The Nature Conservancy is working on a plan that would invest
Already, the Chinese paddlefish, a six-meter-long endemic species, has not been spotted in more than three years in the region and may now be functionally extinct, much like the baiji—a freshwater dolphin—downriver. "Four famous domestic fishes"—the grass, silver, black and big carps—provide protein and a livelihood to more than 10 million Chinese, yet they are dwindling in the stretch of river beneath the Three Gorges Dam, victims of the dam's development and overfishing, says Daqing Chen of the Yangtze River Fisheries Research Institute.
The solution, according to the Conservancy, is to plan hydropower development on a watershed level rather than allowing the proliferation of projects from various levels of government: county, township, city, provincial and even national. "There's wildcat dam development going on. At some level, it's out of control," says Brian Richter, director of the environmental group's Global Freshwater Program, adding that the proliferation of dams of all sizes are "just getting built in an uncoordinated fashion."
As a result, a coalition of Chinese scientists and environmentalists signed a petition this May calling for a halt to "overdevelopment" of hydropower in the
The problem is not dams per se. It is the lack of planning. After all, building hydropower will also enable the proliferation of intermittent renewable energy sources, such as wind and solar. "Xiluodu [Dam] could be used to stabilize against wind and solar to a very large degree because of its size and because it's got another reservoir downstream that can dampen out any fluctuations,"
Of course, there is also the specter of floods. Inundations in 1931 and 1954 killed hundreds of thousands along the lower Yangtze and a similar flood in 1998 displaced at least 1.8 million people. Therefore, one of the primary reasons to build Three Gorges Dam, in addition to hydropower and improved shipping channels, was to restrain the periodic, devastating flooding of the Yangtze.
But a river basin regime that also restores some of the natural floodplains—without displacing the rich rice paddies and vegetable fields that provide 60 percent of the country's food supply—could also generate more power. After all, preparing for floods means lowering water levels in the reservoir to allow for extra water, resulting in reduced hydropower output. Allowing the Three Gorges reservoir to remain at a higher water level, for example, by opening some flood storage downstream could "generate $1 billion more in hydropower revenue," Richter argues.
The key would be to inundate several hundred thousand hectares of the agricultural lands periodically during times of flood to provide as much as 15 billion cubic meters of floodwater storage—three-quarters of the 20 billion cubic meters of flood control offered by the Three Gorges reservoir itself.
But it would also involve temporarily relocating the inhabitants of these lands through early warning and compensating them for lost harvest—something China already does, such as during the 1998 flood. And some of the $1 billion in extra hydropower revenues could go into a proposed compensation fund for such displacement and lost crops, Richter argues, a plan for which Goldman Sachs is preparing a feasibility study. "Using floodplains to store floods is more reliable, safer and more economical," Richter says.
Such a plan would also more closely mimic the natural flow of the river, which is naturally high during spring and summer and low in winter, the opposite of the flow pattern imposed by dams such as Three Gorges that attempt to reserve room for floodwaters. "Fish reproduction in the Yangtze and other rivers depends on the maintenance of natural flow patterns, because it is these that set the cues for breeding and stimulate breeding migrations," Hong Kong's Dudgeon notes.
Such river basin regimes could prove vital in other areas of the world undergoing a hydropower boom, as well, Richter says. In
And it might help ameliorate or avoid some of the other impacts from dam construction now coming to the surface. "More than 100 miles of [Three Gorges] reservoir banks are at risk of collapsing. More than 50 percent of the reservoir area is affected by erosion and an additional 500,000 people will need to be relocated," says Peter Bosshard, policy director at International Rivers, a dam watchdog group. Further downstream there is also erosion in the Yangtze's delta as well as seawater intrusion. "
Despite these concerns, dam construction continues. Coffer dams—a temporary barrier that allows work on a permanent dam to proceed—are already in place for many projects, such as the Ahai Dam on the Jinsha River, closing off yet more sections of the waterway.
"It's not just dams versus no dams,"