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A landscape assessment and associated dataset of stream confluences for the conterminous U.S.

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Abstract Stream confluences are important components of fluvial networks. Hydraulic forces meeting at stream confluences often produce changes in streambed morphology and sediment distribution, and these changes often increase habitat heterogeneity relative to upstream and downstream locations. Increases in habitat heterogeneity at stream confluences have led some to identify them as biological hotspots. Despite their potential ecological importance, there are relatively few empirical studies documenting ecological patterns across the upstream-confluence-downstream gradient. To facilitate more studies of the ecological value and role of stream confluences in fluvial networks, we have produced a database of stream confluences and their associated watershed attributes for the conterminous United States. The database includes 1,085,629 stream confluences and 383 attributes for each confluence that are organized into 15 database tables for both tributary and mainstem upstream catchments (“local” watersheds) and watersheds. Themes represented by the database tables include hydrology (e.g., stream order), land cover and land cover change, geology (e.g., calcium content of underlying lithosphere), physical condition (e.g., precipitation), measures of ecological integrity, and stressors (e.g., impaired streams). Additionally, we used the measures of ecological integrity to assess the condition of the stream confluences. Aside from a generally positive east-to-west gradient in ecological condition, we found that approximately one-third of the confluences have markedly contrasting ecological conditions between mainstem and tributary, catchment and watershed, or both. Abstract Stream confluences are important components of fluvial networks. Hydraulic forces meeting at stream confluences often produce changes in streambed morphology and sediment distribution, and these changes often increase habitat heterogeneity relative to upstream and downstream locations. Increases in habitat heterogeneity at stream confluences have led some to identify them as biological hotspots. Despite their potential ecological importance, there are relatively few empirical studies documenting ecological patterns across the upstream-confluence-downstream gradient. To facilitate more studies of the ecological value and role of stream confluences in fluvial networks, we have produced a database of stream confluences and their associated watershed attributes for the conterminous United States. The database includes 1,085,629 stream confluences and 383 attributes for each confluence that are organized into 15 database tables for both tributary and mainstem upstream catchments (“local” watersheds) and watersheds. Themes represented by the database tables include hydrology (e.g., stream order), land cover and land cover change, geology (e.g., calcium content of underlying lithosphere), physical condition (e.g., precipitation), measures of ecological integrity, and stressors (e.g., impaired streams). Additionally, we used the measures of ecological integrity to assess the condition of the stream confluences. Aside from a generally positive east-to-west gradient in ecological condition, we found that approximately one-third of the confluences have markedly contrasting ecological conditions between mainstem and tributary, catchment and watershed, or both.

Impact/Purpose

Stream confluences are important components of fluvial networks that have been identified as biological hotspots. Stream confluences are an overlooked aspect of Clean Water Act reporting. More research is needed to determine how they can be used and incorporated in Clean Water Act reporting (e.g, 305b). The database created as part of the project provides a framework for incorporating stream confluences in Clean Water Act reporting.

Citation

Ebert, D., J. Wickham, A. Neale, AND M. Mehaffey. A landscape assessment and associated dataset of stream confluences for the conterminous U.S. American Water Resources Association, Middleburg, VA, 57(2):315-327, (2020). [DOI: 10.1111/1752-1688.12899]

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DOI: A landscape assessment and associated dataset of stream confluences for the conterminous U.S.
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Last updated on April 26, 2021
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