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Hydrologic Landscape Characterization for the Pacific Northwest, USA
Citation:
Leibowitz, S., R. Comeleo, P. Wigington, Jr., M. Weber, E. Sproles, AND K. Sawicz. Hydrologic Landscape Characterization for the Pacific Northwest, USA. JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION. American Water Resources Association, Middleburg, VA, 52(2):473-493, (2016).
Impact/Purpose:
Under the Air, Climate, and Energy National Program, work has been done to expand the hydrologic landscapes (HLs) concept and to develop an approach for using it to address streamflow vulnerability from climate change. This work has included development of the HL classification framework and its application to Oregon, use of the HL classes to predict where a simple lumped hydrologic model accurately predicts daily streamflow, use of HL information to model the presence of cold-water patches at tributary confluences, and combining Oregon HL results with temperature and precipitation predictions to examine how HLs would vary as a result of climate change. As a part of the current work, the HL approach has been expanded to the Pacific Northwest (Oregon, Washington, and Idaho) based on a revision of the approach that makes it more broadly applicable. This revised approach has several advantages compared with the original approach: it is not limited to areas that have an aquifer permeability map; it uses a flexible approach to converting a nationally available geospatial dataset into assessment units; and it is more robust. These improvements should allow the revised HL approach to be applied more often in situations requiring hydrologic classification, and allow greater confidence in results. This effort paves the way for a climate change analysis for the Pacific Northwest that is currently underway, as well as expansion into the southwest (California, Arizona, and Nevada). This contributes to the ACE MA-2 249 product “Report on the utility of the hydrologic landscape approach for streamflow vulnerability assessments.”
Description:
Hydrologic classification can help address some of the challenges facing catchment hydrology. Wigington et al. (2013) developed a hydrologic landscape (HL) approach to classification that was applied to the state of Oregon. Several characteristics limited its applicability outside of Oregon. Here we update that approach so that it is more broadly applicable and apply the updated approach to the Pacific Northwest (PNW, i.e., Oregon, Washington, and Idaho). Specific changes incorporated are: the use of assessment units based on National Hydrography Dataset Plus V2 catchments; a modified snowmelt model validated over a broader area; an aquifer permeability index that does not require pre-existing aquifer permeability maps; and aquifer and soil permeability classes based on uniform criteria. Comparison of Oregon results for the revised and original approaches found fewer and larger assessment units, loss of summer seasonality, and changes in rankings and proportions of aquifer and soil permeability classes. Differences could be explained by three factors: an increased assessment unit size; a reduced number of permeability classes; and use of smaller cutoff values for the permeability classes. The improvements reported here should allow the revised HL approach to be applied more often in situations requiring hydrologic classification, and allow greater confidence in results. We also apply the map results to the development of hydrologic landscape regions.
