国三峡大坝正面临可能最为艰巨的挑战，前所未有的暴雨导 致水位上升，也引起人们对大坝能否控制长江洪峰的疑虑。
官方媒体周一发出警告 说，持续数周的暴雨造成长江及其支流的水位超过了1998年的水平；当时洪水造成4,150人死亡，迫使1,830万人转移安置。
新华社 援引中国长江三峡集团公司一位管理人士的话报导，最早在周一或周二，三峡大坝的洪峰可能达到每秒6.9万立方米，是去年大坝全面投入使用以来的最大洪峰。 中国长江三峡集团公司负责管理三峡大坝工程。1998年，每秒5万立方米的洪峰淹没了长江沿岸的大片地区。
长江水利委员会防汛抗旱办公室 调度处处长王井泉说，三峡大坝的设计能力为每秒11万立方米的洪峰流量。他还说，目前水库的水位低于175米高的最高设计水位，大坝的涡轮发电机尚未全面 运行，因为该地区此前一直遭受着旱灾。
7月初以来，中国很多地区连降暴雨，引发泥石流 和洪灾，目前已经证实有至少146人死亡，约40人失踪。很多受灾者来自重庆周边的山区。重庆位于640公里长三峡水库的西侧上游。官员们说，全国总计有 约12.4万间房屋损毁，130多万人被迫转移安置。估计经济损失达人民币295亿元（合44亿美元）。
沿长江这一最重要的内陆航道之一 的航运可能会因暴雨而中断。该航道对往中国中部和西部运输原材料和货物至关重要。航运部门说，如果流量超过每秒4.5万立方米，本周末他们可能会关闸。
根 据国家媒体消息，周日中国国务院副总理回良玉命令在中国中部另一重要航道淮河沿岸进行紧急防洪准备。中国今年的雨量比去年最高多出50%。
洪 灾重新引发了就建设三峡大坝的主要争议之一。近一个世纪以前建立大坝作为制服洪灾并产生能源的想法出现以来，批评家就说其环境、社会和经济成本过高。
尽 管反对者进行了异乎寻常的大声批评，但大坝还是在1992年得到批准。支持者说，大坝将产生清洁电力，开通供大型船只航行的长江新航道，并能防范危害极大 的洪灾。在人们普遍指责腐败行为和滥用政府资金的声讨声中，长江沿岸100多万居民被重新安置，为大坝让路。直到近些年，政府才将对大坝的批评声浪压制下 去。
自那以来，发电和控制洪水的目标有时会互相矛盾，调控水位就会减少发电量。监管该流域的政府机构──长江水利委员会 （Changjiang Water Resources Commission）的成员过去曾报怨说，长江三峡集团这一国营企业在运营大坝的时候将利润置于防洪之前。
长江三峡集团联合环保组织大 自然保护协会（Nature Conservancy）研究如何改进对漫滩和三峡上游几座大坝的管理，此举显示出其艰难的平衡举措。环保人士希望增加流向下游的水流量，以帮助恢复受大 坝损坏的生态系统。水费增加可以带来数亿美元的电力收入，不过这也增加了洪灾的风险。
但批评家指出，大坝不能防范多数洪灾，因为最大的问 题是由森林砍伐、地表侵蚀和湿地减少造成的。湿地就像是河岸天然的海绵状缓冲体。
大坝在洪水控制方面是否有效的问题是最最重要的。这座大 坝还被批评要为越来越多的滑坡和可能导致地震的地震活动负责。
政府还试图鼓励大坝周围贫困地区100多万居民移民到附近城市，以减轻因最 初为大坝让路进行强制移民而加剧的过度拥挤和污染问题。
China's Three Gorges Dam is facing what could be its toughest challenge, as record-breaking storms raise water levels and doubts about the dam's ability to control floods on the Yangtze River.
State media on Monday warned that weeks of torrential rains have raised water in the Yangtze and its tributaries above levels seen in 1998 when floods killed 4,150 people and forced the evacuation of another 18.3 million people.
Water flow at the dam could hit 69,000 cubic meters a second as early as Monday or Tuesday, the greatest water surge since the dam became fully operational last year, said an official with the China Three Gorges Corp., which manages the project, according to state-run Xinhua news agency. In 1998, water flowing at 50,000 cubic meters a second devastated huge areas along the banks of the Yangtze in central China.
Wang Jingquan, a drought and flood prevention official at the Changjiang Water Resources Commission, said the Three Gorges Dam was designed to withstand up to 110,000 cubic meters of water a second. He added that reservoir levels are below the maximum capacity of 175 meter high and that the dam's electricity turbines haven't been operating at full capacity because the area had been suffering from drought.
At least 146 people have been confirmed dead and some 40 are missing since the start of July after landslides and flooding in storm-hit regions across China. Many victims are from the hilly terrain around Chongqing, the city located upstream on the western end of the 640-kilometer-long reservoir created by the Three Gorges Dam. All told, some 124,000 homes have been destroyed, and more than 1.3 million forced to relocate nationwide, officials said. Economic losses are estimated at 29.5 billion yuan, or $4.4 billion.
Shipping along one of the most important inland waterways -- essential for ferrying raw materials and goods into central and western China -- could be disrupted by the floods. Shipping authorities said over the weekend they could close locks on the dam if water speeds exceed 45,000 cubic meters a second.
On Sunday, Chinese Vice Premier Hui Liangyu ordered emergency flood preparations along the Huai River, another major waterway in central China, now bursting over with as much as 50% more rainfall than last year, according to state media.
The flooding reignites one of the key debates over the construction of the Three Gorges Dam. Since the idea of the dam's inception nearly a century ago as a way to tame deadly flooding and generate energy, critics have said its environmental, social and economic costs would be too high.
Despite unusually vocal criticism by opponents, the dam was approved in 1992. Proponents said it would generate clean electricity and open up new swaths of the Yangtze for navigation by bigger boats while preventing lethal flooding. More than a million residents along the banks of the Yangtze were relocated to make way for the reservoir, among widespread allegations of corruption and misuse of government funds. Until recent years, the government cracked down on any critics of the dam.
Since then, the goals of power generation and flood control have sometimes been in conflict. Regulating water levels can reduce how much electricity is made. In the past, members of the Changjiang Water Resources Commission, the government body that oversees the river basin, have complained that the state-owned company running the dam puts profits ahead of flood prevention.
In a move acknowledging its difficult balancing act, China Three Gorges joined with the environmental group the Nature Conservancy to study how to improve management of floodplains and several dams upriver from the Three Gorges. Environmentalists want to increase the amount of water flowing downstream to help restore ecosystems damaged by the dams. Increased water rates could bring in hundreds of millions more dollars in electricity revenue, though could raise the risk of flooding.
But critics say the dam can't prevent most flooding anyway because the biggest problem is caused by deforestation, erosion and loss of wetlands that act as a natural spongelike buffer along river banks.
Questions about the dam's usefulness in flood control comes on top of other issues. The giant dam has also been blamed for increased landslides and seismic activity that could trigger an earthquake.
The government also is trying to encourage more than a million residents in the impoverished region around the reservoir to move into nearby cities to alleviate overcrowding and pollution worsened by the initial forced migration to make way for the dam.