Hydrology and Water Resources: Current Research
Paleoreconstructions of Pacific Northwest Streamflow
- Alan Hamlet, UW Climate Impacts Group
- Jeremy Littell, UW Climate Impacts Group
- Nate Mantua, UW Climate Impacts Group
Paleoclimatic streamflow reconstructions derived from proxy records (such as tree-rings) play an important role in water resources planning and management. In Idaho, for example, an unprecedented (in the historic record) five-year drought has severely stressed existing water resources and water resources policy. What is the return interval of such extreme events? Longer records based on paleoclimatic reconstructions can provide a better understanding of the probability of distributions of such extreme events by dramatically increasing the temporal sample size.
Previous efforts to reconstruct streamflow in the Columbia River in the Pacific Northwest (Gedelof et al. 2004) showed limited ability to reproduce interannual variations in streamflow, and at least one drought period in the 1800s identified in the study may not have actually occurred according to newspaper records (instead tree growth may have been suppressed by cold temperatures or other factors). Although these effects may prove to be partly related to fundamental characteristics of PNW climate, in this study we will attempt to improve on these existing methods both by increasing the number and quality of proxy records available, and by exploring the potential to systematically select amongst these tree ring records to provide the best results using, for example, hydrologic modeling studies as a guide for key runoff producing areas at different times of year. A broader range of climatic zones and spatial scales will also be investigated.
The project will also explore the application of current and projected temperature effects on annual and seasonal streamflow timing to the paleo reconstructions in an attempt to provide “paleoecological climate change scenarios” suitable for long-range planning studies.
The first year of the project has focused on developing new (and updating existing) tree ring chronologies over the PNW. We are now moving forward in the second phase of the project to use these primary products to predict streamflow in selected areas of the PNW back several centuries.
NOAA RISA (Western Water Assessment, CLIMAS), Idaho Department of Water Resources, U.S. Bureau of Reclamation (Regional District, Boise), Seattle Water Supply, Portland Water Bureau
NOAA Science Applications Research Project
For publications on climate impacts on PNW water resources, please see CIG Publications.