Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 1, 2003
Publication Date: January 15, 2004
Citation: Paige, G.B., Stone, J.J., Smith, J.R., Kennedy, J.R. 2004. The walnut gulch rainfall simulator: A computer controlled variable intensity rainfall simulator. Applied Engineering in Agriculture. 20(1):25-31. Interpretive Summary: A new research tool was developed to help scientists and land managers measure runoff and erosion processes on rangelands. The Walnut Gulch Rainfall Simulator is a portable, computer controlled, variable intensity rainfall simulator to conduct rainfall-runoff-erosion studies. The simulator has a single central oscillating boom and applies water over a 2m by 6.1m area. The simulator can apply rainfall rates between 13- and 178 mm/hr, in 13 mm/hr increments across the plot. Water use is minimized by recycling the water that is not sprayed directly on the plot. The large range of intensities is an improvement over existing rainfall simulators and is an important addition for rainfall ¿runoff-erosion studies in the semiarid southwest where there is a large range of intensities in natural rainfall. The simulator has been tested in both laboratory and field applications. The development of this new simulator will assist scientists quantify hydrologic and erosion processes on rangelands. Results from field studies using this new simulator will benfit both scientists and land managers.
Technical Abstract: The Walnut Gulch Rainfall Simulator (WGRS) is a portable, computer controlled, variable intensity rainfall simulator for rainfall-runoff-erosion research on rangelands. The WGRS was developed with the objective to quantify the relationship between rainfall intensity and steady state infiltration rate and to determine how that relationship affects sediment transport by overland flow. The simulator has a single central oscillating boom and applies water over a 2m by 6.1m area. Two important improvements have been made to the oscillating boom simulator design. First, a computer controlled stepper motor is used to control the oscillations and minimize the variability of the water application across the plot. Second, the spray time and sequence of nozzle operation are controlled by 3-way solenoids to minimize the delay time between oscillations at low application rates. The simulator applies rainfall rates between 13- and 178 mm/hr, in 13 mm/hr increments, with a coefficient of variability of 11 percent across the plot. Water use is minimized by recycling the water that is not sprayed directly on the plot. The simulator has been tested in both laboratory and field applications. The runoff and erosion generated from the WGRS are shown to be comparable with those generated using the rotating boom simulator.