INFILTRATION AND RUNOFF PLOT STUDIES ON RANGELANDS: RAINFALL SIMULATOR EXPERIMENTS

Authors: Stone, Jeffry; PAIGE, V. - UNIV. OF ARIZ.

Submitted to: USDA Agricultural Reseach Service Infiltration Conference
Publication Type: Proceedings
Publication Acceptance Date: 7/29/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Infiltration studies have been conducted on rangelands for over 60 years and have both increased our knowledge of the infiltration process and have reveled significant gaps in knowledge of that infiltration process. Important results which have been obtained are that infiltration rates are different under extremes of grazing intensity and the rates can be much greater under vegetative canopy than outside the canopy. However, finding quantitative explanations for these results has been less than successful. In part, the reason lies in that infiltration on anything large than a point scale is not measured directly but computed as a difference between rainfall and runoff. A second reason is that to date a satisfactory infiltration model for rangelands has not been developed. Recommendations for future research include defining rainfall characteristics in the Western U.S., determining a correspondence between natural and simulated plot response, determining a correspondence among simulators at point, small plot, and large plot scales, quantifying partial area response, conducting interior plot measurements, and examining all hydrograph components.

Technical Abstract: Rangeland plot studies have been used since the 1930's to investigate fundamentals of the rainfall/runoff/erosion process and the grazing management and land characteristics impacts on these processes. The vast majority of studies have reported final infiltration rates on small plots as affected by either grazing intensity or vegetation and soil surface characteristics. Most of the studies are consistent with each other on a qualitative basis. That is, interspace areas have lower infiltration rates than under canopy areas and infiltration rates under high intensity grazing are lower than under low intensity grazing. Ascribing reasons for these differences is more problematic and the studies are less consistent. Parameterization of infiltration models has also been less than successful. The reasons for the lack of success are probably because infiltration is not measured directly and none of the experiments were expressly designed to measure infiltration parameters. Considerations for future research include defining rainfall characteristics in the Western U.S., determining a correspondence between natural and simulated plot response, determining a correspondence among simulators at point, small plot, and large plot scales, quantifying partial area response, conducting interior plot measurements, and examining all hydrograph components.