When you could build a reservoir and keep it filled?
|This hydrograph shows a comparison of water stage around the two Hoover Dams: Lake Okeechobee in Florida and Lake Mead on the Colorado River. The two men (blue and red) are both 6-ft tall to provide a similar scale of reference to each reservoirs.|
Not the case any longer for Hoover's dam and dike.
A changing climate (i.e. Hoover Dam) and protecting the levee (i.e. Hoover Dike) have kept water levels down in these reservoirs below their historic norms. Lake Mead recently touched down at its lowest level since the dam was built in the 1930s. At capacity it can hold 28 million acre feet. Under current conditions it's closer to ten. Meanwhile, Lake Okeechobee has rarely even risen to the base of the perimeter levee in recent years to keep pressure off the leaky dike (currently under repair). Its current volume is around 4 million acre feet.
Notice the scales:
Lake Meade has steadily dropped over 150 feet over the past two decades to its current drought stage. Meanwhile bounces between flood and drought stage (a difference of 8 ft) every few years.