Comment: 11:06 - 12:25 (01:19)
Source: Annenberg/CPB Resources - Earth Revealed - 22. Wind, Dust and Deserts
Keywords: "Art Montana", desert, drainage, "drainage pattern", river, Nile, Africa, Niger, "Colorado River", "United States", stream, soil, pond, lake, evaporation, sand, "Mojave Desert", California, "Mojave River", "San Bernardino Mountains", "Soda Lake"
Our transcription: The phenomenon of flash flooding in the desert raises the question of drainage.
Where does all the water go?
Drainage in deserts is characterized by internal drainage, and by this I mean it has a drainage pattern that isn't connected to the regional drainage pattern.
Only the largest rivers in the world: the Nile in North Africa, and the Niger in West Africa, and the Colorado in the southwestern United States persist as they flow through deserts.
For the most part, any river or stream flowing into a desert will sink into the soil and disappear or else collect in a pond or a salt lake.
Generally, deserts streams disappear in desert because of the high rate of evaporation and also because of the unconsolidated nature of the sand and sediment of the floor.
A good example, I think, is the Mojave Desert in California where there's only one stream, that's the Mojave River involved in the drainage pattern.
It rises on the edge of the Mojave in the San Bernardino Mountains, flows out into the Mojave, but for the most part is underground -- there's only three places where in a normal year it surfaces.
In wet years like 1969, '78, '80, and '83, it was above ground most of the way; in fact, it flowed over into Soda Lake and became and honest-to-goodness lake.
Geology School Keywords