Wednesday, 9 November 2005
15

Dynamism in the Predominant Mechanism of Infiltration on Desert Pavements as a Function of Surface Age.

Darren Meadows, Michael Young, and Eric McDonald. Desert Research Institute, 755 E. Flamingo Rd, Las Vegas, NV 89119

Desert pavements are landscape-scale surfaces common in arid environments worldwide. They consist of a mosaic of stones at the surface, which are embedded in an underlying silt-rich vesicular A (Av) horizon. The Av horizon is a continuous soil layer comprised of individual, polygonal soil peds. Pavements range in age from <5 - >100 kA. As the surface ages, the Av horizon accretes due to an influx of eolian material. This accretion is accompanied by an increase in structure and a concomitant decrease in infiltration capacity. We describe the results of tension disc infiltration experiments on pavements of three different ages. Although the saturated hydraulic conductivity decreases only slightly with age, the n parameter exhibits a large increase with age for the surfaces we sampled. This implies that the minute interped cracks become more developed as the surface ages. Individual ped hydraulic properties are compared with values derived from field infiltrometer tests to more fully assess the impact of the interped region as a function of surface age. We also show results from dye tracer experiments on the same surfaces. The tracer experiments show clear evidence of preferential flow through the interped cracks. Finally, we discuss implications for arid landscape evolution.

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