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Deschutes River Pilot Assessment

Background

The BSOA project team and National Steering Committee identified the Deschutes Basin as a preferred candidate for a pilot assessment, because it had strong stakeholder interest and sufficient geographic, jurisdictional, and operational complexity for testing assessment tools and methodologies. The DOE’s Pacific Northwest and Oak Ridge National Laboratories (PNNL and ORNL) worked closely with stakeholders in the Deschutes Basin to develop a scenario-based modeling approach to examine tradeoffs among hydropower and environmental opportunities in the context of other water uses. The approach involved developing a daily water-balance model specific to the Deschutes and Crooked river basins that could be used to simulate alternative water-management scenarios. Scenarios were constructed through a scoping process aimed at identifying actions, measurements, and resource levels that expose opportunities and tensions in the system.

Deschutes River Map

Physical Description

Named “River of the Falls” (“Riviere des Chutes” in French), the Deschutes River originates in the Cascade Mountains of Central Oregon and runs 252 miles to join the Columbia River near The Dalles, Oregon. The Deschutes River Basin covers approximately 10,700 square miles and is the second largest river basin in Oregon. Major tributaries to the Deschutes River include the Little Deschutes River, Fall River, Spring River, Crooked River, Metolius River, Whychus Creek, and Tumalo Creek.

The Deschutes River Basin can be divided into three subbasins; Upper and Lower Deschutes and Crooked River basins. This assessment focused on the Upper Deschutes and the Crooked River. The Pelton-Round Butte Hydroelectric Project is included as part of the assessment area because of its importance for energy and the environment throughout the Deschutes and Crooked River subbasins.

Hydrology

The Deschutes River exhibits very stable natural flow regimes and infrequent flooding. The upper and middle reaches of the Deschutes River are primarily spring-fed due to permeable volcanic geology that allows rain and snowmelt to quickly infiltrate. Many of the Crooked River’s headwater tributaries are also spring-fed, although much of the system is fed by surface inputs.

The Deschutes River’s naturally stable flow regime has been altered by the development of reservoirs and irrigation canals. Water stored in the Upper Deschutes reservoirs during the winter is used for irrigation downstream in the summer. This action leads to lowered winter flows in the Upper Deschutes and irrigation-season diversions at Bend often result in low flows in the Middle Deschutes during summer. In addition, as much as 50 percent of the water that is diverted from the Deschutes River in irrigation canals seeps into the ground before it reaches the point of intended use.

The Crooked River flow regime has been significantly altered by the creation of dams and withdrawals for irrigation and municipal needs. Diversions during irrigation season often result in low summer flows in the Lower Crooked River.

Hydropower Opportunities

Two of the most likely opportunities for increasing hydropower in the Deschutes Basin are 1) adding new generation at existing non-powered dams and large diversions, and 2) adding new generation in existing irrigation canals and conduits.

Key Environmental Concerns

The Upper Deschutes River has experienced a degradation of aquatic habitats, riparian vegetation, and water quality due to alterations in the natural hydrograph (NPCC 2004). Flow alterations in the Upper Deschutes River and main tributaries to the Middle Deschutes (Tumalo and Whychus creeks) have contributed to degradation of water quality in the Middle Deschutes River (NPCC 2004). Changes to the hydrologic regime of the Lower Crooked River have contributed to the degradation of water quality and aquatic habitat.

Reports

Basin Scale Opportunity Assesment

Resources

Contacts