USGS Scientific Investigations Report 2007-5282

Prepared in cooperation with the Tennessee Department of Transportation

A Modified Siphon Sampler for Shallow Water

By Timothy H. Diehl

U.S. Geological Survey Scientific Investigations Report 2007-5282, 11 pages (Published online January 2008)

This report is available in PDF format: SIR 2007-5282 (Opens the PDF file in a new window. ) (1.75 MB)

Cover thumbnailA modified siphon sampler (or "single-stage sampler") was developed to sample shallow water at closely spaced vertical intervals. The modified design uses horizontal rather than vertical sample bottles. Previous siphon samplers are limited to water about 20 centimeters (cm) or more in depth; the modified design can sample water 10 cm deep. Several mounting options were used to deploy the modified siphon sampler in shallow bedrock streams of Middle Tennessee, while minimizing alteration of the stream bed.

Sampling characteristics and limitations of the modified design are similar to those of the original design. Testing showed that the modified sampler collects unbiased samples of suspended silt and clay. Similarity of the intake to the original siphon sampler suggests that the modified sampler would probably take downward-biased samples of suspended sand. Like other siphon samplers, it does not sample isokinetically, and the efficiency of sand sampling can be expected to change with flow velocity. The sampler needs to be located in the main flow of the stream, and is subject to damage from rapid flow and floating debris.

Water traps were added to the air vents to detect the flow of water through the sampler, which can cause a strong upward bias in sampled suspended-sediment concentration. Water did flow through the sampler, in some cases even when the top of the air vent remained above water. Air vents need to be extended well above maximum water level to prevent flow through the sampler.





Design and Operation

Comparison to DH-48


References Cited

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Suggested citation: Diehl, T.H., 2008, A modified siphon sampler for shallow water: U.S. Geological Survey Scientific Investigations Report 20075282, 11 p.

For more information, please contact Timothy H. Diehl.

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