The view from the top of the luxurious Morgan Centre down onto Beijing's Olympic Green is breath-taking, There, far below, lies the stunning' bird nest' Olympic Stadium. Right next to it is the equally mesmerizing National Aquatics Center, known as the Water Cube. The Aquatics Center poses one critical question: where will all the water to fill this bold but massive architectural masterpiece' and to supply the Games' come from? One can drive a hundred miles in any direction from Beijing and never cross a healthy river. Heading north to Shanxi province, one passes river after river that has dried up. And in 80 percent of those Shanxi rivers that are still flowing, water quality is' unfit for human contact' or for agricultural or industrial use. As you drive south across Hebei and Henan provinces, the situation is no better. Reaching the famed Marco Polo Bridge over the Yongding River, we crossed our first parched(干裂的) riverbed. From there to the Yellow River, we traversed many legendary rivers that show as blue lines on the map; all of them are now almost bone dry. All that remains to memorialize these watercourses are highway bridges, left behind like vestigial organs. The Yellow River itself, once known as' China's Sorrow' because of its natural tendency to flood, killing millions, has in Henan been reduced to a modest-size channel. At its lower reaches in Shandong, it is not uncommon for the river to cease flowing into the Bohai Sea altogether. What is the answer for the 250 million thirsty people who live on the North China Plain? Drought has forced farmers to turn to groundwater. But over extraction has caused water tables to fall by as much as 10 feet a year. Desperate officials have taken to making substantial investments in' precipitation-inducement(引导水分凝结) technologies', or cloud seeding. Using aircraft, meteorological balloons and even rockets and artillery shells, they've been attempting to shoot passing clouds full of rainmaking chemicals. The China Meteorological Administration reports that hundreds of aircraft and thousands of rockets and shells are used each year in the effort. Such campaigns have been only modestly successful and have created tensions between different localities, each claiming that clouds are being' intercepted' upwind by the other and their precious moisture stolen! Then there is the monumental South-North Water Transfer Project. But some environmentalists fear that shifting the increasingly polluted water of the Yangtze northward will also introduce a whole host of new toxic pollutants to the breadbasket of China. No one knows what the consequences of all these Promethean(独创的) efforts will be. In the truly magnificent facilities being built for the Olympics, one can see a dear manifestation of this understandable urge to restore Chinese greatness. The question is whether China's limited natural-resource base can sustain the magnitude of such an ambition. With water, the country is confronting the edge of one very inflexible environmental envelope. Beijing's glorious Water Cube is a symbol both of China's remarkable accomplishments, and its all-too-pressing limits. By saying' One can drive a hundred miles in any direction from Beijing and never cross a healthy river' (Line 1, Paragraph 2), the author implies that ______.