in the continental United States, what happens to rain that falls west of the Great Continenetal Divide? Rain that falls east?
http://en.wikipedia.org/wiki/Continental_divide
West flows west -- where will it end up?
East flows east and southeast -- where will it end up?
In the continental United States, the Great Continental Divide serves as a boundary that separates the direction in which rivers flow. It determines whether the rainwater will eventually reach the Pacific Ocean or the Atlantic Ocean.
When rain falls west of the Great Continental Divide, the water usually follows the path of the rivers towards the Pacific Ocean. This includes major rivers like the Columbia, Colorado, and Snake Rivers. Most of the water from rain that falls in this region eventually ends up in the Pacific Ocean, either directly or after joining larger rivers.
On the other hand, rain that falls east of the Great Continental Divide follows the path of the rivers towards the Atlantic Ocean. Major rivers on the eastern side of the divide, such as the Mississippi, Ohio, and Hudson Rivers, collect rainwater and drain into the Atlantic Ocean. Additionally, some of the rainwater that falls east of the divide can flow into the Gulf of Mexico via the Mississippi River.
Understanding the direction of river flow in North America greatly helps in predicting where rainwater that falls in a particular region will ultimately end up.