February 9, 2015
What is the water cycle? “The water cycle describes the existence and movement of water on, in, and above the Earth. Earth’s water is always in movement and is always changing states, from liquid to vapor to ice and back again. The water cycle has been working for billions of years and all life on Earth depends on it continuing to work; the Earth would be a pretty stale place without it” (USGS). The water cycle does not have a starting point, but since most of Earth’s water comes from the oceans where it will begin. “The sun, which drives the water cycle, heats water in the oceans. ...view middle of the document...
Some of the water infiltrates into the ground and replenishes aquifers (saturated subsurface rock), which store huge amounts of freshwater for long periods of time. Some infiltration stays close to the land surface and can seep back into surface-water bodies (and the ocean) as groundwater discharge, and some groundwater finds openings in the land surface and emerges as freshwater springs. Yet more groundwater is absorbed by plant roots to end up as evapotranspiration from the leaves. Over time, though, all of this water keeps moving, some to reenter the ocean, where the water cycle “begins” (USGS).
Levees have been a popular flood-control measure. Levees are dikes constructed of earth, stone, or mortar at varying distances from the riverbank to protect residential, industrial, and agricultural property from floodwaters. “Pros of levees are, they have effectively controlled flooding along the Mississippi River, and prevented at $250 billion and a ten-to-one return on the cumulative cost of twenty-five billion. The levees also help maintain river depth that permits extensive barge traffic, which is invaluable to the nation’s economy and to the U.S. position in world trade. The protection has also afforded by the levees has made possible extensive agricultural, industrial, commercial and residential development very close to riverbanks” (Chiras, Reganold). The cons of levees are the flood damaged has increased, the system is not structurally perfect, 1,400 that have been built has not been able to withstand the surging waters, some are too weak, and levees increase rivers velocity and water pressure. If a levee ruptures, the damage and loss of life will be more than if the levee had never been built.
“For years, water supplies have been expanded by building new dams to impound river water. This water was then stored and used during the year. A far most cost-effective and environmentally sound approach, say many experts, is water conservation” (Chiras, Reganold). Dams influence the hydrologic cycle, because they hold water and allow it to recycle its self. The water seeps down into the ground, and runs through the...