Citation:

HUGHES, R. M., P. R. KAUFMANN, AND M. H. WEBER. National and regional comparisons between Strahler order and stream size. JOURNAL OF THE NORTH AMERICAN BENTHOLOGICAL SOCIETY. North American Benthological Society, Lawrence, KS, 30(1):103-121, (2011).

Impact/Purpose:

Water body size is one of the most important factors affecting the structure and function of aquatic ecosystems.

Description:

Water body size is one of the most important factors affecting the structure and function of aquatic ecosystems. The categorical variable, Strahler stream order, is frequently used as an indirect estimate of stream size. Other indirect estimates of stream size, such as catchment area and distance to source are also frequently used by stream ecologists. However, streams are bodies of flowing water and continuous measures of stream size, such as discharge, stream cross sectional area, and stream width and depth are preferable indicators of stream size. Furthermore, these continuous values are often readily available in digital format, or easily and accurately measured in the field. We used data from 2226 U.S. stream sites, ranging from first to eighth order (at 1:100,000 scale), to assess whether stream order is a reliable indicator of stream size, relative to continuous stream size measures. Strahler order accounted for 48-91% of the variability in the alternative size measures considered here. But within individual Strahler orders, the alternative measures varied by 0 - 9 and 0 - 8 orders of magnitude at national and regional scales, respectively. Similarly, the same size measure value could occur in 1 - 7 different stream orders at a national scale and in some regions. We therefore conclude that Strahler order is often associated with stream size, but that multiple, continuous measures of stream size will provide superior accuracy and precision. However, the finite number of reaches with equal Strahler order and the ease of extracting them from national hydrographic data

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