Erosion in the Rio Puerco
Water: driver of erosion
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.
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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.
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.