Publications - Scientific Investigations Report 2008-5124
U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2008-5124
Prepared in cooperation with the
BUREAU OF RECLAMATION
By Mark C. Mastin
The Bureau of Reclamation has implemented a long-term planning study of potential water-storage alternatives in the Yakima River Basin, which includes planning for climate change effects on available water resources in the basin. Previously constructed watershed models for the Yakima River Basin were used to simulate changes in unregulated streamflow under two warmer climate scenarios, one representing a 1ºC increase in the annual air temperature over current conditions (plus one scenario) and one representing a 2ºC increase in the annual air temperature over current conditions (plus two scenario). Simulations were done for water years 1981 through 2005 and the results were compared to simulated unregulated runoff for the same period using recorded daily precipitation, and minimum and maximum air temperatures (base conditions). Precipitation was not altered for the two warmer climate change scenarios.
Simulated annual runoff for the plus one and plus two scenarios decreased modestly
from the base conditions, but the seasonal distribution and the general pattern
of runoff proved to be highly sensitive to temperature changes throughout the
basin. Seasonally increased runoff was simulated during the late autumn and
winter months for both the plus one and plus two scenarios compared to base
conditions. Comparisons at six principal regulatory locations in the basin showed
that the maximum percentage increases in runoff over the base conditions during
December to March varied from 24 to 48 percent for the plus one scenario and
59 to 94 percent for the plus two scenario. During late spring and summer months,
significantly decreased runoff was simulated at these sites for both scenarios
compared to base conditions. Simulated maximum decreases in runoff occurred
during June and July, and the changes ranged from -22 to -51 percent for the
plus one scenario and -44 to -76 percent for the plus two scenario. Differences
in total annual runoff at these sites ranged from -1.4 to -3.9 percent for the
plus one scenario and from -2.5 to -8.2 percent for the plus two scenario. The
percent change of the monthly mean runoff for both scenarios from the base conditions
at many points in the basin will be used in a water-management model developed
by the Bureau of Reclamation to assess various storage alternatives.
Abstract
Introduction
Imposed Climate Changes
Watershed Models
Simulated Runoff Results
Summary
References Cited
Appendix A
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Send questions or comments about this report to the author, M.C. Mastin , (253) 552-1609.
For more information about USGS activities in Washington, visit the USGS USGS Washington Water Science Center home page.