So we have programs around the world that are helping cities learn how to both reduce the amount of pollution and also finance water treatment systems that will purify the water, similar to the kind of systems we have in North America. We also promote the preservation of forests upstream in the watershed, which helps to regulate the water and keep it clean. If you destroy a watershed in its upper reaches everything will change, including the availability of fish, all the way down to where the water reaches the ocean. So when water is taken out of a river, we work with countries on how to most effectively use the water for irrigation systems, use the water for industrial purposes, use the water for human consumption, and how to clean it up when its put back into the system. In most instances, countries also lose transportation and a tremendous amount of the best agricultural land in the world.
Dams also displace cities and people, because many people choose to live near rivers.
The dams themselves provide substantial benefits for a very limited period of time. No dam is permanent. They all silt up at some point. Egypt's Aswan Dam provides hydroelectric power. At the same time, as a result of the dam changing the freshwater flow upstream, we've seen a tremendous die-off of fisheries along the Nile River and an 80 percent reduction in the sardine population of the Mediterranean Sea.