Dam These Facts

Sunday
Dams are old. History’s oldest known dam, the Jawa Dam in present-day Jordan, was built about 2,400 years ago. The oldest known still-operational dam is the Lake Homs Dam (AKA Quatinah Barrage), built between 1319 and 1304 BC. Remarkably, it is one of many still-working dams, mostly in Spain, Japan, and India, now nearly 2 millennia old.
Monday
China boasts both the largest and most dams on Earth, over double that of #2 United States. Fully 45% of all dams in the world are in China.
Tuesday
Massive government-built hydroelectric dams may dominate headlines and imagination, but about half of all dams worldwide are for irrigation projects. Hydroelectric dams are a distant second at about 17%. Also, the large majority of dams are privately owned, at least in the United States.
Wednesday
Dams occasionally collapse, sometimes with tragic consequences. The worst dam breaches have killed thousands, with one especially horrific 1975 collapse in China killing an estimated 171,000 and causing history’s third largest flood. However, the structure itself is not always to blame. Often the surrounding rock in which the dam is anchored simply cannot bear such extraordinary water pressure and gives way.
Thursday
Dams, dikes, and levees all restrain water, but aren’t the same. Dikes are wet on one side and “reclaim” land, keeping water off of land which would otherwise be underwater. A levee is also meant to be wet on just one side, but is more of a flood control device than one to reclaim wet land. Dams have water on both sides, but often with a much higher level on one side than the other.
Friday
Besides humans, only beavers build dams. With their felled-tree dam and “lodge” homes, they get a cozy, insulated, two-chamber, two-exit fortress against predators and also create a pond for still water, perfect for storing food in the unfrozen water at the bottom during winter months.
Saturday
There are four basic types of dams. Embankment dams and gravity dams, built of earth and rock vs. concrete, respectively, rely on the structure’s weight to restrain the water. Buttress dams are reinforced with separate downstream supports. Arch dams are curved and comparatively thin, as they transmit the weight of the water to surrounding rock walls.



