Spatial Digital Database for the Geologic Map of Oregon

Walker, George; MacLeod, N.S.; Miller, Robert J.; Raines, Gary L.; Connors, Katherine A.

doi:10.3133/ofr200367

Cited by 21 publications

(17 citation statements)

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“…To further test our interpretation of k as primarily a metric of geologically mediated drainage efficiency, we correlated k with aquifer permeability for 58 (of which 13 included in this study) Oregon watersheds. The aquifer permeability data for Oregon (Wigington, et al , ) were developed based on the correspondence between lithology (Walker et al , ) and measured values of aquifer unit hydraulic conductivity (Gonthier, 1984; McFarland, ). We found a significant negative correlation between k and aquifer permeability (Spearman's r = −0.35, P = 0.007) but no correlation between k and drainage area (Spearman's r = −0.03, P = 0.81).…”

Section: Watershed Classification Frameworkmentioning

confidence: 99%

Coupling snowpack and groundwater dynamics to interpret historical streamflow trends in the western United States

Safeeq

Grant

Lewis

et al. 2013

Hydrological Processes

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A key challenge for resource and land managers is predicting the consequences of climate warming on streamflow and water resources. During the last century in the western United States, significant reductions in snowpack and earlier snowmelt have led to an increase in the fraction of annual streamflow during winter and a decline in the summer. Previous work has identified elevation as it relates to snowpack dynamics as the primary control on streamflow sensitivity to warming. But along with changes in the timing of snowpack accumulation and melt, summer streamflows are also sensitive to intrinsic, geologically mediated differences in the efficiency of landscapes in transforming recharge (either as rain or snow) into discharge; we term this latter factor drainage efficiency. Here we explore the conjunction of drainage efficiency and snowpack dynamics in interpreting retrospective trends in summer streamflow during 1950–2010 using daily streamflow from 81 watersheds across the western United States. The recession constant (k) and fraction of precipitation falling as snow (Sf) were used as metrics of deep groundwater and overall precipitation regime (rain and/or snow), respectively. This conjunctive analysis indicates that summer streamflows in watersheds that drain slowly from deep groundwater and receive precipitation as snow are most sensitive to climate warming. During the spring, however, watersheds that drain rapidly and receive precipitation as snow are most sensitive to climate warming. Our results indicate that not all trends in western United States are associated with changes in snowpack dynamics; we observe declining streamflow in late fall and winter in rain‐dominated watersheds as well. These empirical findings support both theory and hydrologic modelling and have implications for how streamflow sensitivity to warming is interpreted across broad regions. Copyright © 2012 John Wiley & Sons, Ltd.

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Section: Watershed Classification Frameworkmentioning

confidence: 99%

Coupling snowpack and groundwater dynamics to interpret historical streamflow trends in the western United States

Safeeq

Grant

Lewis

et al. 2013

Hydrological Processes

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“…1) to facilitate geographical analysis. The central region is defined by the pumice zone, based on the Oregon geology map (Walker et al 2003), which has a different ecology, often with lodgepole pine on flats and ponderosa pine or dry mixed-conifer forests on rises (Kerr 1913). The two other regions extend north and south to state borders.…”

Section: Study Areamentioning

confidence: 99%

Implications of spatially extensive historical data from surveys for restoring dry forests of Oregon's eastern Cascades

Baker

2012

Ecosphere

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Abstract. Dry western forests (e.g., ponderosa pine and mixed conifer) were thought to have been historically old and park-like, maintained by low-severity fires, and to have become denser and more prone to high-severity fire. In the Pacific Northwest, early aerial photos (primarily in Washington), showed that dry forests instead had variable-severity fires and forest structure, but more detail is needed. Here I used pre-1900 General Land Office Surveys, with new methods that allow accurate reconstruction of detailed forest structure, to test eight hypotheses about historical structure and fire across about 400,000 ha of dry forests in Oregon's eastern Cascades. The reconstructions show that only about 13.5% of these forests had low tree density. Forests instead were generally dense (mean ¼ 249 trees/ha), but density varied by a factor of 2-4 across about 25,000-ha areas. Shade-tolerant firs historically were 17% of trees, dominated about 12% of forest area, and were common in forest understories. Understory trees and shrubs dominated on 83.5%, and were dense across 44.8% of forest area. Small trees (10-40 cm dbh) were .50% of trees across 72.3% of forest area. Low-severity fire dominated on only 23.5%, mixed-severity fire on 50.2%, and high-severity fire on 26.2% of forest area. Historical fire included modest-rotation (29-78 years) lowseverity and long-rotation (435 years) high-severity fire. Given historical variability in fire and forest structure, an ecological approach to restoration would restore fuels and manage for variable-severity fires, rather than reduce fuels to lower fire risk. Modest reduction in white fir/grand fir and an increase in large snags, down wood, and large trees would enhance recovery from past extensive logging and increase resiliency to future global change. These forests can be maintained by wildland fire use, coupled, near infrastructure, with prescribed fires that mimic historical low-severity fires.

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“…In the original Oregon HL classification (Wigington et al, 2013), a digital GIS dataset of aquifer permeability was created from existing paper aquifer unit maps for eastern (Gonthier, 1985) and western JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION (McFarland, 1983) Oregon. Aquifer subunit descriptions and estimated hydraulic conductivity values for aquifer subunits from these two paper maps were transferred onto a digital state geologic map (Walker et al, 2003). Based on the distributions of estimated hydraulic conductivity values in the state, the aquifer subunits were combined into low (≤1.5 m/day), moderate (>1.5 and ≤3.1 m/day), and high (>3.1 m/day) aquifer permeability classes.…”

Section: Aquifer Permeabilitymentioning

confidence: 99%

Hydrologic Landscape Characterization for the Pacific Northwest, USA

Leibowitz

Comeleo

Wigington

et al. 2016

J American Water Resour Assoc

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We update the Wigington et al. (2013) hydrologic landscape (HL) approach to make it more broadly applicable and apply the revised 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 preexisting 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 distributions of the revised HLs in five groups of Oregon rivers were similar to the original HLs but less variable. 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.

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Spatial Digital Database for the Geologic Map of Oregon

Cited by 21 publications

References 0 publications

Coupling snowpack and groundwater dynamics to interpret historical streamflow trends in the western United States

Coupling snowpack and groundwater dynamics to interpret historical streamflow trends in the western United States

Implications of spatially extensive historical data from surveys for restoring dry forests of Oregon's eastern Cascades

Hydrologic Landscape Characterization for the Pacific Northwest, USA

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