Similarity of stream width distributions across headwater systems
The morphology and abundance of streams control the rates of hydraulic and biogeochemical exchange between streams, groundwater, and the atmosphere. In large river systems, the relationship between river width and abundance is fractal, such that narrow rivers are proportionally more common than wider rivers. However, in headwater systems, where many biogeochemical reactions are most rapid, the relationship between stream width and abundance is unknown. To constrain this uncertainty, we surveyed stream hydromorphology (wetted width and length) in several headwater stream networks across North America and New Zealand. Here, we find a strikingly consistent lognormal statistical distribution of stream width, including a characteristic most abundant stream width of 32 ± 7 cm independent of discharge or physiographic conditions. We propose a hydromorphic model that can be used to more accurately estimate the hydromorphology of streams, with significant impact on the understanding of the hydraulic, ecological, and biogeochemical functions of stream networks.
© 2018 The Author(s). This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. Received: 25 July 2017; Accepted: 12 January 2018; Published online: 09 February 2018. Data availability: All the codes used in the analysis and production of figures in this paper can be obtained at https://github.com/geoallen/streamWidthAnalysis2017/. The stream width measurements, from which the lognormal distributions are derived, are available on a Zenodo digital repository (doi:10.5281/zenodo.1034384). Financial support for this research was provided by NASA New Investigator Program grant #NNX12AQ77G, a UNC Geological Sciences Graduate Student Fellowship, and a Geological Society of America Graduate Student Research Grant to George Allen. Emily Beckham and Elizabeth Henry assisted with fieldwork. Dr. Margaret Zimmer and Dr. Brian McGlynn helped facilitate fieldwork and provided stream gage data in the Stony Creek Research Watershed. Dr. Xiao Yang assisted with theoretical derivations. Dr. Jeremy Jones provided Caribou Creek stream gage data. Author Contributions: G.H.A. and T.M.P. conceived the research idea. G.H.A. designed and performed the analysis, drafted the figures, and wrote the manuscript with input from all coauthors. G.H.A. and E.A.B. conducted the fieldwork, with help from A.T. and D.B. M.P.L. and C.J.G. helped with theory and D.B. calculated carbon fluxes. The authors declare no competing financial interests.
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