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What are rivers  sustained by during periods when rain does not fall?A) evaporationB)...

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homer-simpson | Student, Grade 9 | (Level 1) Honors

Posted February 20, 2012 at 3:58 AM via web

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What are rivers  sustained by during periods when rain does not fall?

A) evaporation
B) transpirated water
C) groundwater
D) runoff

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pacorz | High School Teacher | (Level 3) Educator

Posted February 20, 2012 at 4:38 AM (Answer #1)

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Most rivers are sustained by both groundwater and runoff. Surface runoff is a major contributor after a rain, but runoff also can result from snow or ice melting, which can last through much of the summer at high altitudes. Additionally, some runoff may be captured and retained for a time by wetlands or impoundment areas, and may feed the river's flow for some period of time after the last precipitation has fallen.

Groundwater will continue to sustain a stream's flow even when there is no precipitation. Water contained in an aquifer can flow to the surface as a spring or seep, or can fill a lake or river basin from beneath. Aquifers occur wherever geological conditions are right, and an aquifer can be the headwaters of a river.


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