A Study of Rainfall Simulators, Runoff and Erosion Processes, and Nutrient Yields on Selected Sites in Arizona and New Mexico

Estimation of runoff and sediment yield from small, ungaged watersheds is a difficult hydrologic task. Process oriented mathematical models can be an important part in the solution of this task. Models, however, require some information which is directly related to the hydrologic processes occurring on the watershed. Rainfall simulation is an important experimental technique for gathering such information.

This technical report contains the results of a study on the utility of using rainfall simulation in southwestern watersheds. Two different simulators were compared on three sites. At one site, three simulators were used, and one of the simulators was used to gather data at three additional sites. A small area simulator, 1 square meter, and two large area simulators, approximately 32.5 square meters, were operated for a total of about 74 plot experiments. One of the simulators was operated as part of the USDA – ARS Water Erosion Prediction Project.

Analysis of the data indicates that the simulators provide similar results for infiltration characteristics, and that sediment yields were about 4.0 times higher for the small simulator. Numerous water chemistry samples were analyzed to determine potential nutrient loadings from forest and range lands to water bodies in New Mexico.