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COMPARISON OF DRIP-FLOW/LOW-FLOW MEASURING DEVICES FOR INFILTROMETER RUNOFF MEASUREMENTS
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.orgCitation: Transactions of the ASAE. VOL. 43(6): 1489-1498 . (doi: 10.13031/2013.3048) @2000
Authors: J. V. Bonta, V. C. Goyal
Keywords: Infiltration, Infiltrometer, Spatial variability, Hydrology, GIS, Instrumentation
Runoff is generated on landscapes in a deterministic and random, but unquantifiable manner, and measurements of the spatial variability of infiltration and seepage under natural-precipitation conditions are highly desirable. Runoff from small natural-precipitation infiltrometer plots (0.25 m 2 ) under natural conditions can be merely drip flows, or they can be larger flows when runoff is produced simultaneously from high-intensity rains and seepage. A study of a drip-flow/low-flow nozzle/rotor flow-measuring system that met design requirements for runoff measurement is presented. Comparison of different nozzle configurations led to the selection of the rotor of a Price current meter, in combination with a unique nozzle that incorporated a drip diverter, an internal flow baffle, and drip-control silicone beads. The best nozzle/rotor combination yielded a rating curve with a resolution less than design requirements, and worked well with flows as high as ~6 L min 1 , greater than design requirements. A combined function using linear segments for low flows, and a 4th degree polynomial for high flows, comprised the rating curve. The average residual error about the function was 0.113 L min 1 . Unsteady flow tests with the nozzle showed that the rating curve and nozzle/rotor assembly worked well, with the median error in volume of 21 mL for 12 synthesized events. The device is a standalone measuring system that can be placed anywhere on the landscape, and only electrical pulses, representing rotor-rotation speed require measurement. The nozzle/rotor system can be used for other applications in which drip and low flows need to be measured, such as for rain gauges, percolation flows from lysimeters, spring flows, etc.(Download PDF) (Export to EndNotes)