Miniature rain simulator for field measurement of soil infiltration

In studies of erosion, runoff, and infiltration, high soil variability may demand many replicate measurements and rapid, inexpensive methodology. We developed a drop-forming rainfall simulator in which pow through long, coiled capillary drip tubes is controlled by an adjustable Mariotte-type bubbling tube. These rain simulators are inexpensive, rugged, simple to operate, easily transported, and require minimal maintenance. Responses to pressure head and water temperature changes were determined for two simulators using tap water. Flow response to pressure head changes corresponded closely to that predicted by Poiseuille's Law. Response to increasing water temperatures was somewhat less than predicted, due to formation of bubbles in the capillary tubes. Simulators incorporating long, coiled capillary tubes can provide combinations of ION flow rates and Large drop sizes, or a desired range of flow rates when appropriate drip tube diameters, lengths, and numbers of tubes per unit area are combined.