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Oregon Hydrologic Landscapes: An Approach for Broadscale Hydrologic Classification
Citation:
Wigington, J. Oregon Hydrologic Landscapes: An Approach for Broadscale Hydrologic Classification. Presented at American Geophysical Union (AGU) Fall Meeting, December 03 - 07, 2012.
Impact/Purpose:
To better understand hydrologic behavior of Oregon streams and wetlands, we developed a hydrologic landscape (HL) classification approach that describes factors of climate-watershed systems that control the magnitude and delivery of water to and through watersheds to stream networks. We used a statistical approach to cluster 30 streams with long-term streamflow records into groups with similar streamflow characteristics. We found that the stream clusters had distinct distributions of HLs and could be used to explain the hydrologic behavior of the streams. We believe the Oregon HL approach has potential as a useful framework for comparing hydrologic attributes of streams and rivers in the Pacific Northwest and throughout the United States. It can also be used to make broadscale assessments of areas vulnerable to streamflow change because of climate change.
Description:
Gaged streams represent only a small percentage of watershed hydrologic conditions throughout the Unites States and globe, but there is a growing need for hydrologic classification systems that can serve as the foundation for broad-scale assessments of the hydrologic functions of landscapes and watersheds. I present a hydrologic landscape (HL) classification approach for Oregon based on factors of climate-watershed systems that control the hydrologic characteristics of watersheds. More than 5000 assessment units (incremental watersheds - headwater watersheds or areas draining directly into streams reaches) were delineated across the state. Each assessment unit was classified according to indices of annual climate, climate seasonality, aquifer permeability, terrain, and soil permeability. To determine the usefulness of HLs in estimating stream hydrologic behavior, 30 streams with long-term streamflow gauging records and without major diversions and impoundments were identified. K-mean cluster analysis was used to create independent groups of streams based on the shapes of their annual hydrographs. Comparison of the stream clusters and HL distributions within watersheds of the clusters showed that the Oregon HL approach has the ability to provide information about the expected hydrologic behavior of HLs and larger streams based on watershed HL composition. The HL conceptual framework developed for Oregon, has potential to serve as the basis for comparing hydrologic attributes of watersheds and streams across broad areas such as the Pacific Northwest or United States.