HR: 15:00h
AN: GC52A-06 INVITED     [PDF]
TI: Columbia River Flow And Drought Since 1750
AU: * Gedalof, Z
EM: zeev@uvtrl.geog.uvic.ca
AF: University of Guelph, Department of Geography, Guelph, ON N1G 2W1 Canada
AU: Peterson, D L
AF: USDA Forest Service, Pacific Northwest Research Station 400 N 34th Street, Suite 201, Seattle, WA 98103 United States
AU: Mantua, N J
AF: University of Washington, Climate Impacts Group Joint Institute for the Study of the Atmosphere and Oceans Box 354235, Seattle, WA 98195 United States
AB: A network of drought sensitive tree-ring chronologies is used to reconstruct flow on the Columbia River at The Dalles, Oregon, since 1750. The reconstruction explains 30 percent of the variability in mean water-year flow, with a moderate fraction of unexplained variance caused by underestimates of the most severe low-flow events. Residual statistics from the tree-ring reconstruction, as well as an identically specified reconstruction using instrumental records, exhibit a positive trend over the twentieth century. This finding suggests that the relationship between drought and streamflow has changed, consistent with results from hydrologic models. Both the reconstructed streamflow and the models suggest that changes in land cover over the 20th century have led to increases in runoff relative to precipitation. Lowpass filtering the reconstructed flow record suggests that persistent low flows during the 1840s were probably the most severe of the past 250 years, but that flows during the 1930s were nearly as extreme. The period from 1950 to 1987 is anomalous in the context of this record for having no notable multiyear drought events. A comparison of the flow reconstruction to paleoproxy records of the Pacific Decadal Oscillation (PDO) and El Ni\~{n}o / Southern Oscillation (ENSO) supports a strong 20th century link between large-scale circulation and streamflow, but suggests that this link is very weak prior to 1900.
DE: 1812 Drought
DE: 1833 Hydroclimatology
DE: 1860 Runoff and streamflow
DE: 3344 Paleoclimatology
SC: Global Climate Change [GC]
MN: 2003 Fall Meeting