Submitted to: Pendleton Station Field Day
Publication Type: Experiment Station
Publication Acceptance Date: 3/18/1996
Publication Date: N/A
Interpretive Summary: The amount and type of rain that falls is different from one part of the continent to another. Rainfall simulation is a tool to aid in soil and water conservation research. Rainfall is simulated by spraying water through nozzles designed to create water droplets that very closely resemble natural rain. Generally, the area covered is not very large, but the simulated rainfall can be applied to several locations at one time. This technique can be used to test the soil and water conservation attributes of varying farming methods and soil conditions. Many of the rainfall simulators constructed in the past were designed to reproduce high intensity rainfall typical to summer storms in the Midwest and Southwest. Erosion causing events in the Pacific Northwest are different from those areas. Here, the worst case is a low intensity rain falling onto frozen soil. Prior to our investigations, only one rainfall simulator had been developed for the low intensity rainfall of the Pacific Northwest. We have improved upon its design to aid in our soil and water conservation research. With the new design we are able to evaluate treatments in larger areas and to have greater control of the rainfall simulator performance.
Technical Abstract: Rainfall patterns and intensity are substantially different in the inland Pacific Northwest than other parts of the USA. In order to investigate the effect of rainfall on soil erosion, especially rainfall on frozen soils, we have constructed and tested a rainfall simulator based upon the rotating disk design. Our Northwest Rainfall Simulator has several improvements and new features compared to the previous rainfall simulator design used for erosion research in the Pacific Northwest. The new simulator produces rainfall over a larger area than the older Palouse Simulator. In addition, it is designed to be operated in moderately windy conditions at temperatures from slightly below freezing up to 100 F. Nozzle pressure and rainfall intensity controls are also improved. Electronic data loggers on the new simulator monitor nozzle pressure, air, soil, and water temperature, and runoff. Rainfall distribution test results from the new simulator compare favorably with results obtained from evaluation of the old simulator. This improved rainfall simulator will greatly aid in estimating soil erosion and evaluating management practices used to reduce erosion events.