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Title: Long-term snow, climate and streamflow trends from at the Reynolds Creek Experimental Watershed, Owyhee Mountains, Idaho, United States

item Marks, Daniel
item Seyfried, Mark

Submitted to: Water Resources Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/2010
Publication Date: 6/23/2010
Citation: Nayak, A., Marks, D.G., Chandler, D., Seyfried, M.S. 2010. Long-Term Snow, Climate and Streamflow Trends from at the Reynolds Creek Experimental Watershed, Owyhee Mountains, Idaho, United States. Water Resources Research,46, W06519, doi: 10.1029/2008WR007525.

Interpretive Summary: 45 years of carefully measured data on climate, precipitation, snow and streamflow were used to determine how global warming has affected water resources in the Reynolds Creek Experimental Watershed. During the last 5 decades total annual precipitation and streamflow have not changed, but there is now more rain and less snow, resulting in more winter and less summer streamflow. The snow season is shorter, and the amount of water stored in the seasonal snowcover is reduced. This analysis will have a significant impact on how water resources are managed in the region. If these trends continue soil moisture, streamflow and the animals and plants that depend on them will be negatively impacted.

Technical Abstract: Forty-five water years (1962 – 2006) of carefully measured data on temperature, precipitation, snow, and streamflow for valley bottom, mid-elevation, and high elevation sites within the Reynolds Creek Experimental Watershed (RCEW), located in the state of Idaho, USA, were analyzed to evaluate the extent and magnitude of the impact of climate warming on the hydrology and related resources in interior northwestern United States. This analysis shows significant trends of increasing temperature at all elevations, with larger increases in daily minimum than daily maximum. The proportion of snow to rain has decreased at all elevations, with the largest and most significant decreases at mid- and low elevations. Maximum seasonal snow water equivalent has decreased at all elevations, again with the most significant decreases at lower elevations, and the length of the snow season has decreased by nearly a month. All trends show a significant elevation gradient in either timing or magnitude. Though inter-annual variability is large, there has been no change in water year total precipitation or streamflow. Streamflow shows a seasonal shift, stronger at high elevations and delayed at lower elevations, to larger winter and early spring flows and reduced late spring and summer flows.