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Impacts of 21st‐Century Climate Change on Hydrologic Extremes in the Pacific Northwest Region of North America
Author(s) -
Tohver Ingrid M.,
Hamlet Alan F.,
Lee SeYeun
Publication year - 2014
Publication title -
jawra journal of the american water resources association
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.957
H-Index - 105
eISSN - 1752-1688
pISSN - 1093-474X
DOI - 10.1111/jawr.12199
Subject(s) - environmental science , snowpack , precipitation , climate change , evapotranspiration , drainage basin , flood myth , structural basin , climatology , peninsula , global warming , arid , hydrological modelling , flooding (psychology) , climate model , snow , hydrology (agriculture) , geography , geology , oceanography , meteorology , psychology , ecology , paleontology , cartography , geotechnical engineering , archaeology , psychotherapist , biology
Climate change projections for the Pacific Northwest ( PNW ) region of North America include warmer temperatures ( T ), reduced precipitation ( P ) in summer months, and increased P during all other seasons. Using a physically based hydrologic model and an ensemble of statistically downscaled global climate model scenarios produced by the Columbia Basin Climate Change Scenarios Project, we examine the nature of changing hydrologic extremes (floods and low flows) under natural conditions for about 300 river locations in the PNW . The combination of warming, and shifts in seasonal P regimes, results in increased flooding and more intense low flows for most of the basins in the PNW . Flood responses depend on average midwinter T and basin type. Mixed rain and snow basins, with average winter temperatures near freezing, typically show the largest increases in flood risk because of the combined effects of warming (increasing contributing basin area) and more winter P . Decreases in low flows are driven by loss of snowpack, drier summers, and increasing evapotranspiration in the simulations. Energy‐limited basins on the west side of the Cascades show the strongest declines in low flows, whereas more arid, water‐limited basins on the east side of the Cascades show smaller reductions in low flows. A fine‐scale analysis of hydrologic extremes over the Olympic Peninsula echoes the results for the larger rivers discussed above, but provides additional detail about topographic gradients.