Technical Report

Projected climate change impacts on water demand and supply for the City of Corvallis

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  • A report to Carollo Engineers, Inc.
  • This report provides an estimate of the impacts of climate change on factors affecting City of Corvallis (Corvallis) water demand and its primary water supply sources: the Willamette River and Rock Creek. The key climate-related changes (considered in isolation from other changes) are summarized below: -- Projected higher summer temperatures and lower summer rainfall would increase water demand due to higher evaporative demand and desire for comfort during summer. Using irrigation of lawns as an example, approximately an additional 2 inches of water per unit area each summer may be necessary within 30 years, relative to a 1970-1999 baseline, if averaging over the available climate projections. -- While flood magnitudes on the Willamette River are projected to increase, summer low flows are projected to decrease. Both of these projected changes increase the risk of disruption of water supply from the Willamette River and increase the reliance on the management of upstream reservoirs to regulate flows for flood risk management during the wet season and to maintain sufficient supply for all needs (instream and consumptive) during the dry season. Little change is projected in annual water supply from Rock Creek, but future reductions in late spring flow may lead to a shorter time window of availability for water withdrawal. Despite the critical importance of the quality of Corvallis’ water sources, the varying pathways through which climate change can influence harmful algal blooms (HABs) in the Willamette Valley have not been well quantified, though most projected changes (higher temperatures; higher erosion rates from more intense precipitation and large wildfires, and the associated increased nutrient loading in Oregon’s surface waters) point to a higher frequency of HABs. In addition to the impacts on water quantity, one additional conclusion of this report is that there exists a large gap in knowledge of the degree to which climate change will impact the quality of the sources of water upon which Corvallis, and other communities in the Willamette Basin, rely.
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  • Rupp, D. E. (2019). Projected Climate Change Impacts on Water Demand and Supply for the City of Corvallis, Oregon: Report to Carollo Engineers, Inc. Oregon Climate Research Institute, Corvallis, OR.
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