A basin is a depression in the earth's surface that does not allow for water to escape. This means that any water that flows into a 
basin stays there. A basin can be circular or oval-shaped and is usually surrounded by higher ground. The basins in New Mexico are part of the Basin and Range Province, which covers much of Western North America, and are considered to be desert area that is arid, or dry, and receive very little rain each year.
The Basin and Range Province covers about 1/3 of the state and lies to the south of the Rocky Mountain Region. This region occupies the southwest corner of the state. The Rio Grande Rift, which is a major feature of the Basin and Range Province, forms its eastern border in New Mexico.
More more information about the Rio Grande Rift visit» http://en.wikipedia.org/wiki/Rio_Grande_Rift