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| Titel |
A new instrument to measure plot-scale runoff |
| VerfasserIn |
R. D. Stewart, Z. Liu, D. E. Rupp, C. W. Higgins, J. S. Selker |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
2193-0856
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Instrumentation, Methods and Data Systems ; 4, no. 1 ; Nr. 4, no. 1 (2015-03-02), S.57-64 |
| Datensatznummer |
250115233
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| Publikation (Nr.) |
 copernicus.org/gi-4-57-2015.pdf |
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| Zusammenfassung |
| Accurate measurement of the amount and timing of surface runoff at multiple
scales is needed to understand fundamental hydrological processes. At the
plot scale (i.e., length scales on the order of 1–10 m) current methods
for direct measurement of runoff either store the water in a collection
vessel, which is not conducive to long-term monitoring studies, or utilize
expensive installations such as large-scale tipping buckets or flume/weir
systems. We developed an alternative low-cost, robust and reliable
instrument to measure runoff that we call the "Upwelling Bernoulli Tube"
(UBeTube). The UBeTube instrument is a pipe with a slot machined in its side
that is installed vertically at the base of a runoff collection system. The
flow rate through the slot is inferred by measuring the water height within
the pipe. The geometry of the slot can be modified to suit the range of flow
rates expected for a given site; we demonstrate a slot geometry that is
capable of measuring flow rates across more than 3 orders of magnitude
(up to 300 L min−1) while requiring only 30 cm of hydraulic head.
System accuracy is dependent on both the geometry of the slot and the
accuracy of the water level measurements. Using a pressure sensor with
±7 mm accuracy, the mean theoretical error for the demonstrated slot
geometry was ~17% (ranging from errors of more than 50%
at low flow rates to less than 2% at high flow rates), while the observed
error during validation was 1–25%. A simple correction factor reduced
this mean error to 0–14%, and further reductions in error could be
achieved through the use of taller, narrower slot dimensions (which requires
greater head gradients to drive flow) or through more accurate water level
measurements. The UBeTube device has been successfully employed in a
long-term rainfall-runoff study, demonstrating the ability of the instrument
to measure surface runoff across a range of flows and conditions. |
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