A portable, microcomputer-controlled drip infilrometer. I. Design and operation

Abstract

This paper describes a lightweight, portable drip infiltrometer that uses a dripper unit swung from a collapsible aluminium frame. The dripper unit, constructed of plastic tubing and hollow polythene needles, gives a uniform application rate over 1 m2, and no water is wasted outside that area. A microcomputer controls the rate, which can be varied between 1 mm h-1 and 150 mm h-1, and allows a series of rates and times to be preprogrammed to simulate differing types of rainfall. The infiltrometer can be assembled and operating within 15 min and moved to an adjacent plot in 5 min. Laboratory tests showed that the coefficient of variation over the 1 m2 was 2-4% for a wide range of application rates. A field test demonstrated the usefulness of the infiltrometer in following the ponded infiltration rate with time. Calculated sorptivities were lower than those obtained from ponded ring infiltrometer measurements.