1. 200+ Years of Global Dam Development Each point on the globe represents one of 6,000+ dams built from 1800-2010. Dams impact the hydrological cycle and landscape by giving humans greater control of the distribution and use of water. Dams can help control floods, and provide storage of water for hydroelectricity, agriculture, industry, recreation, transportation, and human consumption.

2. Dams impact the structure of landscapes such as riverbeds and deltas. Rivers erode (wear down) the landscape in some areas by moving sediment (sand, silt and clay) to new places. Sediment that settles and builds up at the mouths of rivers forms deltas, which are important habitats for many species. Over 500 million people live on deltas throughout the world! When dams trap sediment upstream, less sediment is transported to deltas, which causes them to shrink. Image credit: MODIS/NASA The image above shows the Mississippi River Delta, which is where the Mississippi River enters the Gulf of Mexico. The image to the right provides a close up look at sediment from the Mississippi River. Mississippi River Delta Image credit: U.S. Army Corps of Engineers

3. Image credit: NASA/Goddard Space Flight Center Scientific Visualization Studio United States Geological Survey Satellite images (left) show the changes in landscape that resulted from the construction of the Three Gorges Dam in China (right), the largest hydroelectric dam in the world. Image credit: https://www.flickr.com/people/44048265@N00