An estimated 2 billion field mice are chomping their way hungrily through crops in 22 counties (districts) around the Dongting Lake in central China’s Hunan province after their homes on islands in the lake were flooded. The local authorities are rushing to build walls and dig ditches to keep the mice away from flood-control dikes and cropland.
In less than three weeks, local people have killed more than 2.25 million mice but the rodents are marching ahead nevertheless. The massive invasion of field mice began on June 23 when the Yangtze River flooded, raising the water level in Dongting Lake and submerging mouse holes on islands in the lake.

This sounds incredulous for us but it is not new for the Chinese. The Yangtze River has been flooding mainland China for thousands of years. But Chinese engineers say they are close to defeating the fury of the river, at last. The massive dam, christened as the Three Gorges Dam, being constructed along China’s Yangtze River will be the world’s largest hydroelectric power generator and one of the few man-made structures visible to the naked eye from space when it is completed in 2009.

NASA’s Landsat satellites have been tracking the construction of this gigantic project ever since it began in 1994. The Yangtze River is the third largest river in the world, stretching more than 3,900 miles across China before reaching its mouth near Shanghai. Historically, it has been prone to massive flooding, overflowing its banks about once every 10 years. The dam is designed to improve flood control on the river and protect the 15 million people and 3.7 million acres of farmland in the lower Yangtze flood plains.

Observations from the NASA-built Landsat satellites provide an overview of the dam's construction. The first image shows the region prior to the start of the project. By 2000, construction along each riverbank was underway, but sediment-filled water still flowed through a narrow channel near the river’s south bank. The 2004 images show limited development of the main wall and the partial filling of the reservoir, including numerous side canyons. By mid-2006, construction of the main wall was completed and a reservoir more than 2 miles (3 kilometers) across had filled just upstream of the dam.