METHODOLOGY: A SIMPLE RAINFALL SIMULATOR AND TRICKLE SYSTEM FOR HYDRO-GEOMORPHOLOGICAL EXPERIMENTS

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Abstract
A simple rainfall simulator is described which consists of stand-alone sprinkling units with cone jet nozzles that spray downward. With a fall height of 4.57 m and water pressure of 67 kPa, the median drop size of the simulated rainfall is 2.40 mm. Rainfall from two units irrigating a 2 by 2.5 m plot has a total kinetic energy of 0.57 J/m2/s which is approximately 90% of the equivalent energy of natural rainfall at the simulation intensity of 72.4 mm/h. To simulate overland flow, perforated trickle pipes were designed that permit overland flow rates to be readily adjusted and closely controlled by simply varying the input water pressure. In field experiments in southern Arizona, rates between 572 to 1400 cm3/s were generated from a 19-mm pipe. Given their low cost, simplicity, and portability, the rainfall simulator and trickle system should be attractive to researchers working in a wide variety of geomorphic environments.