The U.S. has more than 87,000 dams greater than six feet high (and two million overall). While many dams continue to provide benefits such as flood control, irrigation, and water supply, for other dams the cost of maintenance or the negative effects on communities, fish, and tribes justifies their removal.
Dam owners and regulators decide whether to remove a dam by weighing many factors including: the cost of removal and the ability to replace any lost power generation against avoided long-term maintenance; safety concerns; benefits to endangered fish populations; increased recreational and commercial fishing; and restoration of cultural values of nearby tribes.
By 2020, roughly 70% of dams will be more than 50 years old, inviting us to reconsider the value to the public of long-term investments in this infrastructure.
How do nearby bodies of water help to keep the climate of certain areas mild?
A Land and water absorb and store heat at similar rates.
B Water and land temperatures reach extremes of hot and cold.
C Water temperatures change more slowly than land temperatures.
D Land temperatures change more slowly than water temperatures.
Tectonically stable means that this part of the continent has not moved for billions of years. The rock formation is important understanding the history of Earth since its unmoved and untouched state can provide ideas about how the Earth looked like as seen on the layers of the rock formation.
compass rose, sometimes called a windrose or rose of the winds, is a figure on a compass, map, nautical chart, or monument used to display the orientation of the cardinal directions (north, east, south, and west) and their intermediate points.
Simon Bolivar's revolution brought an end to the Spanish rule in South America.
