National Research Program


Climate, drought, and streamflow patterns

During recent decades, droughts of one to three years have affected some parts of the United States but prolonged droughts of the magnitude experienced during the 1930s and 1950s have not occurred. To help the country prepare to face the potential effects of a prolonged drought, USGS scientists, along with colleagues in universities and other government agencies, have been studying regional, National, and global spatial patterns of drought. Coping with a prolonged drought is anticipated to be difficult, particularly in the arid and semi-arid West, where water demand has increased significantly and water supplies are likely be insufficient for demand.

Graphs showing relationship between Colorado River Flow and SOI, PDO, and AMO global climate indices[Time series showing complex relationship between Colorado River Flow and Global Climate Indices. Dry climate periods are within tan bars.]

Where available data on climate and hydrologic conditions in the United States are insufficient, patterns in tree rings are being used to determine patterns of previous droughts.1,2 In 2004, scientists reported being able to account for 74% of the spatial and temporal variance in multidecadal drought frequency over the conterminous United, with more than half attributable to the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO).3 However, scientific knowledge is still insufficient to make reliable drought predictions. A 2005 report on the Colorado River notes that climate, drought and streamflow are linked, but in poorly understood ways. Findings indicate that drought magnitude and persistence patterns are associated with broader hemispheric climate patterns, but the correlations do not provide a clear understanding of long-term precipitation patterns. Although components of the climate system, such as sea-surface temperature of the Atlantic and Pacific oceans, provide some context for understanding variations in precipitation and streamflow, they are insufficient for predicting the fate of the ongoing drought so that currently there is no reliable way to predict how long the early 21st century drought will last in the Colorado River Basin.4

References Cited:
1.Gray, S.T., Betancourt, J.L., Fastie, C.L., and Jackson, S.T., 2003, Patterns and sources of multidecadal oscillations in drought-sensitive tree-ring records from the central and southern Rocky Mountains: Geophysical Research Letters, v. 30, no. 6, p. 49-1 - 49-4.

2.Pederson, G.T., Gray, S.T., Fagre, D.B., and Graumlich, L.J., 2006, Long-duration drought variability and impacts on ecosystem services: Earth Interactions, v. 10, p. 1-28.

3.McCabe, G.J., Palecki, M.A., and Betancourt, J.L., 2004, Pacific and Atlantic Ocean influences on multidecadal drought frequency in the United States: Proceedings of the National Academy of Sciences USA, v. 101, p. 4,136-4,141.

4.Webb, R.H., Hereford, Richard, and McCabe, G.J., 2005, Climatic fluctuations, drought, and flow in the Colorado River, in Gloss, S.P., Lovich, J.E., and Melis, T.S., eds., The State of the Colorado River Ecosystem in Grand Canyon: U.S. Geological Survey Circular 1282, p. 59-69.

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For additional information, see references or contact Julio Betancourt,, Gregory McCabe, or Robert Webb,

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