Weather - the summer monsoon of the Southwest

The Rio Puerco, like many parts of New Mexico and Arizona, is affected by summer monsoons. These are moist flows of air that originate primarily in the Gulf of Mexico; the local manifestation is thunderstorms - exactly the sort of intense rain that can readily move materials and cut channels.

For more information on this topic, please read:
Precipitation Trends and Water Consumption in the Southwestern United States, by Henry Diaz and Craig Anderson.

Water flow - the driver of sediment

Water flow in channels is a prerequisite to the formation of arroyos. When precipitation falls on sand, gravel, or highly fractured rock (such as volcanic rocks that are abundant in the Rio Puerco basin), then the water percolates into the ground and does not create runoff. On the other hand, if rain falls on clay-rich soils that do not readily absorb water, then abundant runoff is produced. Thus, soil infiltration rates are key determinants of the amount of water that flows in channels during and after storms.

Some catchments in the Rio Puerco basin produce 10 times more water than others of the same size and elevation. Some of this discrepancy may be due to differences in precipitation, but runoff generation and channel infiltration are also likely contributing factors.

Tributaries and scaling

The geographic extent of thunderstorms may be a subtle climatic influence over the arroyo cycle in the Rio Puerco. When rain falls simultaneously in the catchments of multiple tributaries, then the downstream convergence of flow may sustain sediment transport for distances greater than would be possible for precipitation in a single catchment. Satellite observations of clouds and Doppler radar precipitation data both provide information about the extent of storms over the Rio Puerco basin, which has few weather stations.

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Next: How do Arroyos Work?

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U.S. Department of the Interior
U.S. Geological Survey
This page is http://esp.cr.usgs.gov/rio_puerco/puerco2/hydrology.html
Maintained by Richard Pelltier
Last modified: 15:04:23 on 15-Mar-2006