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.
- Supporting Information: Figure S1; Table S1 - Download docxData
Figure S1. Net effect from mean annual streamflow and center of timing on...
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POLYGON ((-123.02215576172 48.894518236158, -103.86199951172 48.952268302185, -104.03778076172 44.934668567935, -111.42059326172 45.121021859875, -111.06903076172 44.622731540795, -111.06903076172 41.870583462267, -124.51629638672 41.935998088668, -124.69207763672 48.196302825623, -123.11004638672 48.137683143855, -123.02215576172 48.662849897351))
Water Resources Research
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January 1, 1948 to December 31, 2013
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005:040 - Department of Agriculture - National Research
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005:18 - Agricultural Research Service