Trends and sensitivities of low streamflow extremes to discharge timing and magnitude in Pacific Northwest mountain streams

Journal Article · Sat Jul 02 00:00:00 EDT 2016 · Water Resources Research

DOI:https://doi.org/10.1002/2015WR018125· OSTI ID:1402325

Kormos, Patrick R. ^[1]; Luce, Charles H. ^[2]; Wenger, Seth J. ^[3]; Berghuijs, Wouter R. ^[4]

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1. U.S. Forest Service, Rocky Mountain Research Station Boise Idaho USA, Oak Ridge Institute for Science and Education Oak Ridge Tennessee USA, U.S. Agricultural Research Service, Northwest Watershed Research Center Boise Idaho USA
2. U.S. Forest Service, Rocky Mountain Research Station Boise Idaho USA
3. River Basin Center, Odum School of Ecology University of Georgia Athens Georgia USA
4. Department of Civil Engineering University of Bristol Bristol UK

Abstract Path analyses of historical streamflow data from the Pacific Northwest indicate that the precipitation amount has been the dominant control on the magnitude of low streamflow extremes compared to the air temperature‐affected timing of snowmelt runoff. The relative sensitivities of low streamflow to precipitation and temperature changes have important implications for adaptation planning because global circulation models produce relatively robust estimates of air temperature changes but have large uncertainties in projected precipitation amounts in the Pacific Northwest U.S. Quantile regression analyses indicate that low streamflow extremes from the majority of catchments in this study have declined from 1948 to 2013, which may significantly affect terrestrial and aquatic ecosystems, and water resource management. Trends in the 25th percentile of mean annual streamflow have declined and the center of timing has occurred earlier. We quantify the relative influences of total precipitation and air temperature on the annual low streamflow extremes from 42 stream gauges using mean annual streamflow as a proxy for precipitation amount effects and streamflow center of timing as a proxy for temperature effects on low flow metrics, including 7q10 summer (the minimum 7 day flow during summer with a 10 year return period), mean August , mean September , mean summer , 7q10 winter , and mean winter flow metrics. These methods have the benefit of using only readily available streamflow data, which makes our results robust against systematic errors in high elevation distributed precipitation data. Winter low flow metrics are weakly tied to both mean annual streamflow and center of timing .

• Sponsoring Organization: USDOE
• OSTI ID: 1402325
• Journal Information: Water Resources Research, Journal Name: Water Resources Research Vol. 52 Journal Issue: 7; ISSN 0043-1397
• Publisher: American Geophysical Union (AGU)
• Country of Publication: United States
• Language: English