Spatial Variability of Air and Water Permeability for Two Watersheds in the Mojave and Sonoran Deserts.

A research study was conducted in two arid watersheds in the Mojave and Sonoran Deserts to characterize the spatial variability of air and water permeability according to the evolution of soil forming processes and to determine its effect on infiltration. Air permeability, which is a viable alternative to water- and textured-based methods to rapidly map saturated hydraulic conductivity, was measured using a 20 cm air permeameter.  The ability to measure this important hydraulic property without the use of more cumbersome and time-consuming direct methods may provide a practical approach to generate more complete data to describe hydrologic conditions.  Water permeability was measured using an automated and portable mini-disc tension infiltrometer with a 5 cm base.  Eight measurements of air and water permeability were measured in situ along a 2.5 m transect for 6-8 geomorphic surfaces ranging from young soils found in stream channels to older soils found on desert pavements.  Both air and water permeability decreased with age where the air permeability ranged from 5 to 300 um2.  These results indicate that soil forming processes are important to consider when characterizing watersheds.