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1 March 2007 Using sound pressure to estimate reaeration in streams
Nathaniel Morse, William Breck Bowden, Alexander Hackman, Celia Pruden, Erin Steiner, Elliott Berger
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The reaeration coefficient (k) is an essential and sensitive component of the equations used to calculate whole-stream metabolism (WSM) for a stream reach by the open-channel method. However, the empirical methods used to estimate k (e.g., by propane or sulfur hexafluoride evasion rates) are time consuming and costly. We reasoned that the reaeration rate (the product of k and the dissolved O2 deficit or surplus) and sound level (noise) are related to turbulence in a stream and, thus, sound level should be related to reaeration. We used a simple and inexpensive sound level meter to measure sound levels at a fixed height (30 cm) above key geomorphic features (e.g., pools, riffles, cascades) in several streams in Alaska and Vermont. We calculated a feature-weighted average sound pressure for selected stream reaches based on the proportion of these geomorphic features within each reach. We calculated k in the Alaskan stream reaches based on propane evasion rates and found a strong linear relationship to the feature-weighted average sound pressure (n = 11, r2 = 0.94, p < 0.001). We concluded that the sound pressure method, which requires 0.5 h to complete and relies on inexpensive instrumentation, provides estimates of k that are comparable to estimates from the more resource-intensive volatile gas-evasion method. In the Vermont stream reaches, we were able to create a sound pressure–stage rating curve, similar to a hydrologic rating curve. Combining the k–sound pressure relationship with the sound pressure–stage rating curve holds promise as a way to estimate reaeration continuously, at modest cost and effort, and on a time scale similar to that on which dissolved O2, temperature, and light values are recorded to calculate WSM.

Nathaniel Morse, William Breck Bowden, Alexander Hackman, Celia Pruden, Erin Steiner, and Elliott Berger "Using sound pressure to estimate reaeration in streams," Journal of the North American Benthological Society 26(1), 28-37, (1 March 2007).[28:USPTER]2.0.CO;2
Received: 4 November 2005; Accepted: 6 October 2006; Published: 1 March 2007

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open-system metabolism
primary production
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