An approach for simulating rainfall above the tree canopy at the hillslope scale
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Rainfall simulation is a valuable experimental approach to study hydrologic and erosion processes. Most of the rainfall simulation studies done on arid or semi-arid rangelands have been at the small-plot scale, and rarely with water applied above the tree canopy. A new methodology for simulating rainfall above tree canopies at the hillslope scale is presented. The rainfall simulator that was developed consisted of modular components that are easily transported and installed at remote sites on rugged, brush-covered hillslopes. The simulator manifolds, which are equipped with four sprinkler heads, are supported by individual, telescoping masts that can be extended up to 11 m. The masts that support the manifolds are mounted on base plates, designed to facilitate installation on steep hillslopes. the sprinkler-head manifolds are easily installed on the masts using a quick-connect mounting bracket. The rainfall simulator is capable of simulating rainfall from 25 to 250 mm/h at a height of 11 m. The rainfall simulator was field tested on a 7 x 14 m plot with the masts set at a height of 5 m. For simulated rainfall rates of 25, 51, 76, 102, 127 and 153 mm/h, coefficients of uniformity ranged from 58% to 73%. Median raindrop diameters ranged from 1.7 to 2.4 mm, and associated kinetic energies varied from 16.8 to 25.9 J/m2-mm. The rainfall simulator has performed well with minimum maintenance and proved to be a cost-effective and efficient research tool for replicating natural, above-canopy rainfall in arid and semiarid environments. 2006 American Society of Agricultural and Biological Engineers.