Rios (i.e. rivers)
Yes.
Snake Rivers
The adverb is mainly. It modifies the verb "drain" to say that the rivers do not entirely drain into the valley.
The Rio Grande and Pecos River are the major rivers in New Mexico. The major lakes in New Mexico are Elephant Butte Reservoir, Conchas Lake, and Navajo Reservoir.
Columbia and the Snake Rivers
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.
The Rio Grande and Pecos River are the major rivers in New Mexico. The major lakes in New Mexico are Elephant Butte Reservoir, Conchas Lake, and Navajo Reservoir.
the Magdalena and Cauca
drought
nile river
Lena River