Hydrogeologic controls on streamflow sensitivity to climate variation |
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| Authors: | Anne Jefferson Anne Nolin Sarah Lewis Christina Tague |
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| Institution: | 1. Department of Geography and Earth Sciences, University of North Carolina at Charlotte, 9201 University City Boulevard, Charlotte, NC 28223, USA;2. Department of Geosciences, Oregon State University, 104 Wilkinson Hall, Corvallis OR 97331, USA;3. Bren School of Environmental Science and Management, University of California, Santa Barbara, CA 93106, USA |
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| Abstract: | Climate models project warmer temperatures for the north‐west USA, which will result in reduced snowpacks and decreased summer streamflow. This paper examines how groundwater, snowmelt, and regional climate patterns control discharge at multiple time scales, using historical records from two watersheds with contrasting geological properties and drainage efficiencies. In the groundwater‐dominated watershed, aquifer storage and the associated slow summer recession are responsible for sustaining discharge even when the seasonal or annual water balance is negative, while in the runoff‐dominated watershed subsurface storage is exhausted every summer. There is a significant 1 year cross‐correlation between precipitation and discharge in the groundwater‐dominated watershed (r = 0·52), but climatic factors override geology in controlling the inter‐annual variability of streamflow. Warmer winters and earlier snowmelt over the past 60 years have shifted the hydrograph, resulting in summer recessions lasting 17 days longer, August discharges declining 15%, and autumn minimum discharges declining 11%. The slow recession of groundwater‐dominated streams makes them more sensitive than runoff‐dominated streams to changes in snowmelt amount and timing. Copyright © 2008 John Wiley & Sons, Ltd. |
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| Keywords: | groundwater snowmelt climate variability and change low flows Cascades Oregon |
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