All rivers drain into oceans.
Although, due to humans drawing huge amounts of water for our cities, some rivers dry up before they reach the see nowadays.
Yes.
Snake Rivers
All of the rivers in Siberia tend to flow north. These rivers flow north as they being pulled to drain into the Arctic Ocean.
Rivers provide a pathway to drain all the excess precipitation that is not absorbed by the land or held in lakes. They run into bigger rivers and then, finally, into the ocean.
The adverb is mainly. It modifies the verb "drain" to say that the rivers do not entirely drain into the valley.
Yes, there are rivers in West Virginia. Just like there are rivers in all 49 other states, too.
Gulf of Mexico
Columbia and the Snake Rivers
drought
Lena River
nile river
The Colorado River.