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Significance of trends toward earlier snowmelt runoff, Columbia and Missouri Basin headwaters, western United States
Author(s) -
Moore Johnnie N.,
Harper Joel T.,
Greenwood Mark C.
Publication year - 2007
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2007gl031022
Subject(s) - snowmelt , surface runoff , environmental science , hydrology (agriculture) , precipitation , structural basin , snow , linear relationship , drainage basin , climate change , water year , spring (device) , physical geography , climatology , meteorology , geology , geography , ecology , statistics , cartography , oceanography , paleontology , geotechnical engineering , mathematics , biology , mechanical engineering , engineering
We assess changes in runoff timing over the last 55 years at 21 gages unaffected by human influences, in the headwaters of the Columbia‐Missouri Rivers. Linear regression models and tests for significance that control for “false discoveries” of many tests, combined with a conceptual runoff response model, were used to examine the detailed structure of spring runoff timing. We conclude that only about one third of the gages exhibit significant trends with time but over half of the gages tested show significant relationships with discharge. Therefore, runoff timing is more significantly correlated with annual discharge than with time. This result differs from previous studies of runoff in the western USA that equate linear time trends to a response to global warming. Our results imply that predicting future snowmelt runoff in the northern Rockies will require linking climate mechanisms controlling precipitation, rather than projecting response to simple linear increases in temperature.