Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/1998
Publication Date: N/A
Interpretive Summary: Researchers studying soil and water conservation rely upon a wide range of tools to do their job. One of those tools is the rainfall simulator. The rainfall simulator is used to simulate rain and study how rain erodes soil or how different types management might prevent soil erosion. The Pacific Northwest Rainfall Simulator is designed to simulate rainfall found in the Pacific Northwest (USA). Rainfall in this region falls in small drops and slowly. Consequently, the energy to erode soil is less than found in rainstorms found the southeastern, mid-, southern-, and southwestern- United States. Almost all rainfall simulators were designed to simulate rainstorms in these regions. The Pacific Northwest Rainfall Simulator produces rain that is almost exactly like storms in this region. We developed and tested the simulator to insure that it would produce these storm conditions over the plot areas (1.5 by 9.1 meters) that we use for our research. The simulator consists of four units. Each unit has three nozzles. The rainfall distribution of these three nozzles is very close to the rainfall distribution of one nozzle by itself. This evenness of distribution has not be obtained before. The rainfall simulator will be used to help develop new farming practices and to further our knowledge of soil, plant, and water interactions. Much of this information will be gathered during the critical erosion season in our region between November and March. We have successfully used the simulator in subfreezing temperatures.
Technical Abstract: A rainfall simulator for use in the Pacific Northwest (USA) has been developed. It simulates rainfall with small drop size and at low intensity common to the region. The simulator consists of four units. Each unit simulates rainfall onto a 1.5 m by 9.1 m plot. This plot size is approximately three times larger than the plot size of the simulator formerly used to simulate rain in the Pacific Northwest. Rainfall can be applied at five discreet intensities; 4, 9, 13, 18, and 36 mm h-1. The two lowest rates equal the median and maximum rainfall recorded in ten years at the Columbia Plateau Conservation Research Center, Pendleton OR. The higher rates represent convectional storm that occasionally occur during summer and fall. The simulators were tested for consist and even of rainfall distribution. Values for the Christiansen coefficient of application uniformity ranged between 76 and 81. A value of 100 equals perfect application uniformity, and earlier work with a single nozzle and low application rates produced values of 80. Pressure, and thus quality control, is maintained through a monitoring and adjustment system. Data loggers and sensor units record water temperature and pressure, and air temperature during rainfall simulations. A minimum crew of eight is required to operate all four units simultaneously. The simulator is operational at -5 Co. This rainfall simulator is an appropriate and needed tool for soil and water conservation research in the Pacific Northwest (USA).