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Basin and Range Province: Great Basin
The Basin and Range province’s dynamic fault history has profoundly affected the region’s water drainage system. Most precipitation in the Great Basin falls in the form of snow that melts in the spring. Rain that reaches the ground, or snow that melts, quickly evaporates in the dry desert environment. Some of the water that does not evaporate sinks into the ground to become ground water. The remaining water flows into streams and collects in short-lived lakes called playas on the valley floor and eventually evaporates. Any water that falls as rain or snow into this region does not escape out of it; not one of the streams that originate within this basin ever find an outlet to the ocean. The extent of internal drainage, the area in which surface water cannot reach the ocean, defines the geographic region we call the Great Basin.
The Great Basin’s internal drainage results from blockage of water movement by high fault-created mountains and by lack of sufficient water flow to merge with larger drainages outside of the Great Basin. This internally-drained area occupies approximately 200,000 square miles, including most of Nevada, a large part of Utah, and portions of Idaho, California, and Oregon. Much of the present-day Great Basin would drain to the sea - just as it did in the recent Ice Ages - if there were more rain and snowfall. Great Basin - the geographical and hydrological region comprised of most of Nevada, southern Oregon and Idaho, western Utah, and a little of eastern California. Characterized by internal drainage, this region’s surface water sources evaporate or percolate before the can flow to the ocean.
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