Water Resources of Oregon

USGS Oregon WSC Highlights

Why Is Groundwater Declining So Fast in the Columbia Plateau?

Groundwater from the 44,000-square-mile Columbia Plateau Regional Aquifer, a system in decline since the 1970s, is an essential source of drinking water for nearly 1.3 million people in Idaho, Oregon, and Washington, and of irrigation water for the region’s estimated $6 billion-per-year agricultural industry.

To help resource managers in the region, the USGS Groundwater Resources Program began a study in 2007 of the Columbia Plateau Regional Aquifer System to answer key questions about widespread water-level declines, reductions in groundwater flow into rivers, and the as-yet unknown effects of a changing climate on groundwater resources.

As part of the effort to document changes in the aquifer system, scientists from the USGS Washington and Oregon Water Science Centers compiled water levels measured in about 60,000 wells over the last 100 years. From a subset of the collected information, scientists developed a groundwater-level trend map for a period of widespread groundwater level changes (1968 to 2009). The average rate of change for all wells was 1.9 feet per year of decline, with 72 percent of all wells declining.

View the full study report.

Learn more about the Columbia Plateau Groundwater Availability Study.

Hydrologic Datasets to Aid Water Management in the Upper Klamath Basin

The USGS, in cooperation with several Klamath Basin stakeholders, has developed hydrologic datasets for the upper Klamath Basin of south-central Oregon that can help water managers identify and prioritize water uses that could be voluntarily set aside and reallocated to yield an additional 30,000 acre feet of water to Upper Klamath Lake. The datasets can be used by water managers to display the geographical distribution of evapotranspiration, subirrigation, water rights, streamflow statistics, and irrigation return flow in the upper basin, crucial information for understanding potential impacts of any changes in allocation. Used together, the datasets can help managers determine the relative benefits of retiring water uses and/or redirecting specific water rights to address water-resource issues specified in the Klamath Basin Restoration Agreement.

The KBRA was developed by a diverse group of stakeholders—Federal and State resource management agencies, Tribal representatives, and interest groups. The KBRA has the over-arching goal of providing a comprehensive solution to ecological and water-supply issues in the Klamath Basin. An important element of the KBRA is an Off-Project Water Program (outside of the Bureau of Reclamation’s Klamath Project area, south of Upper Klamath Lake), which was designed to help resolve upper basin water-supply issues. The KBRA has not yet been authorized by Congress; this research was undertaken to help water managers facilitate implementation of KBRA if it is authorized. The datasets, however, will also be of importance to other water-resources research efforts in the upper basin.

Read more about the study and how to obtain the datasets.

Visit the study Web page.

Restoring the Environmental Health of a Regulated River, the Santiam

The Santiam River is a tributary of the Willamette River in northwestern Oregon that drains an area of 1,810 square miles. The U.S. Army Corps of Engineers (USACE) operates four dams in the basin, which are used primarily for flood control, hydropower production, recreation, and water-quality improvement. The Detroit and Big Cliff Dams were constructed in 1953 on the North Santiam River. The Green Peter and Foster Dams were completed in 1967 on the South Santiam River. The impacts of the structures have included a decrease in the frequency and magnitude of floods and an increase in low flows. These changes have altered the geomorphology and ecology of the Santiam River system.

A recently completed USGS study provides a baseline assessment of the hydrology, geomorphology, and effect of streamflow on the ecology of the Santiam River. The assessment was made for the Santiam River environmental flow study, which is a collaborative effort of the U.S. Army Corps of Engineers, The Nature Conservancy, and the U.S. Geological Survey (USGS) under auspices of the Sustainable Rivers Project. In 2002, The Nature Conservancy and the U.S. Army Corps of Engineers began the Sustainable Rivers Project for the purpose of modifying dam operations and implementing environmental flow requirements for various river systems around the country. The study findings will assist water managers and stakeholders in the development of future environmental flow requirements for the Santiam River basin.

Read the report from this study.

Geomorphology, Water Quality, and Habitat in the Mollala River

The Molalla River, a tributary to the Willamette River in nortwestern Oregon, is valued for many attributes, including its runs of winter steelhead and spring Chinook salmon, high-quality drinking water, and, in summer, refreshing swimming holes. Concerns about declining fish runs have generated interest in documenting the current status of the aquatic habitat available for fish and water-quality conditions in the river and how the basin's geomorphology and land use might be contributing to habitat degradation and property damage. To address these issues, the Molalla River Improvement District, Molalla River Watch, Oregon Department of Fish and Wildlife, and others requested that the U.S. Geological Survey (USGS) conduct a geomorphic and aquatic habitat study in the lower Molalla River.

The objectives of this study were to (1) complete a geomorphic and aquatic habitat characterization of the lower Molalla River to understand the factors driving current conditions in the river, (2) characterize the water quality, benthic algae, and invertebrate conditions, and (3) evaluate potential interactions between algal assemblages and the geomorphic and water-quality parameters. In addition, given ongoing concerns about potential nutrient enrichment, bacteria, proliferations of nuisance algae in the river, and impacts on water quality such as low levels of dissolved oxygen and high pH, this study also included two surveys of algal conditions to document current biomass levels and species composition in the lower river during summer. Because of the often strong control that grazing by bottom-dwelling organisms can have on algal populations and their importance as a food resource for fish, qualitative surveys for these organisms were also conducted during algal sampling.

Read the report from this study.

Assessing Trends in Gravel Bar and Channel Morphology in the Rogue River Basin

Several coastal rivers in southwestern Oregon are a source of gravel used as aggregate for road and construction projects and to make concrete. Gravel bars in the Rogue River basin have been used as a local source since at least 1972. The Klamath Mountains, which underlie about half of the basin, are a rich source of gravel in the Rogue and other coastal rivers.

The USGS, in cooperation with the U.S. Army Corps of Engineers and the Oregon Department of State Lands, has completed a reconnaisance study of gravel transport in the Rogue River basin to inform the permitting of instream gravel extraction in Oregon.The study employed various methods to document vertical and lateral channel conditions and trends in the distribution and area of gravel bars over time: review of existing datasets (such as bridge inspection surveys, watershed analyses, and instream gravel-mining records), delineation of bar and channel features from aerial and orthophotographs taken in multiple years, and field observations and particle size measurements in July and September 2010. Findings from these datasets and observations were used to (1) assess the vertical and lateral stability of river segments in the Rogue River basin and identify locations where the channels may be incising, aggrading, prone to migrations, or stable and (2) identify key datasets and issues that are relevant to understanding channel condition and bed-material transport as well as the potential effects of instream gravel extraction on channel condition and bed-material transport in the basin.

Significant findings and the final report from this study can be accessed at http://pubs.usgs.gov/of/2011/1280/. Online reports for the Umpqua River, Hunter Creek, and Chetco River are also available.

Video: Studying the Effects of Emerging Contaminants on the Lower Columbia River Ecosytem

The Columbia River provides important hydroelectric power generation, valuable recreational and tribal fisheries, extensive recreational areas and scenic beauty, and habitat for wildlife and fish. The lower Columbia River below Bonneville is the largest remaining free-flowing reach not impounded by hydroelectric dams, and is critical to the viability of culturally significant fish populations (anadromous and resident) in the Columbia Basin, as well as a myriad of other aquatic and terrestrial organisms. Fish, wildlife, and human populations along the lower Columbia River are exposed to a growing variety of contaminants as a result of increasing urbanization, industrialization, and agricultural development.

The USGS is studying how emerging contaminants, such as polybrominated diphenyl ether flame retardants (PBDEs) and endocrine disrupting compounds (EDCs) impact fish, osprey, and other wildlife in the lower Columbia River basin. Learn more in this video: http://gallery.usgs.gov/videos/427

Video: Shocking! Electrofishing for Largescale Suckers on the Columbia River

The USGS is studying how contaminants such as flame retardants, endocrine disrupting compounds, and other toxins impact fish, osprey, and other wildlife in the basin. As part of that study, USGS biologists collect fish (largescale suckers) to measure concentrations of these compounds in organ tissue and to relate these to contaminant concentrations measured in the foodweb and environment.

Suckers are collected in the open river by using boat-mounted electroshockers to stun and then net the fish. You can see how this is done in a video of a recent collecting trip that can be accessed via either of the following links:

http://www.youtube.com/USGS
http://gallery.usgs.gov/videos/387

Geologic Model of the Columbia River Plateau Supports Studies of Groundwater Availability

The Columbia Plateau regional aquifer system (CPRAS) covers approximately 44,000 mi² of Idaho, Oregon, and Washington. The area supports a 6 billion dollar per year agricultural industry, leading the Nation in the production of apples and nine other commodities. Groundwater availability in the aquifers of the area is a critical water-resource management issue because the water demand for agriculture, economic development, and ecological needs is high.

The primary aquifers of the CPRAS are basaltic lava flows of the Columbia River Basalt Group (CRBG) and overlying basin-fill sediments. Water-resource issues that may affect groundwater availability in the region include (1) widespread water-level declines associated with groundwater withdrawals for irrigation and other uses, (2) reduction in base flow to rivers and associated effects on temperature and water quality, and (3) current and anticipated effects of global climate change on recharge, base flow, and, ultimately, groundwater availability.

The U.S. Geological Survey (USGS) Groundwater Resources program began a study of the CPRAS in 2007 with the broad goals of (1) characterizing the hydrologic status of the system, (2) identifying trends in groundwater storage and use, and (3) quantifying groundwater availability. The study approach includes documenting changes in the hydrologic condition of the system, quantifying the hydrologic budget for the system, updating the regional geologic and hydrogeologic frameworks, and developing a groundwater-flow simulation model for the system. The groundwater flow model will be used to evaluate and test the conceptual model of the system and then will be used to evaluate groundwater availability under alternative development and climate scenarios. A geologic model has been developed to serve as the foundation for the hydrogeologic framework of the groundwater flow model.

Read about the geologic model and access an interactive Web tool that allows a user to view the subsurface geology of the CPRAS.

Listen to and view an interview with the principal investigator on the modeling project.

View descriptions of other Oregon Water Science Center studies.

Report Documents the Age of Groundwater Nationwide

Water "age" in aquifers is a critically important hydrologic variable. The age of a molecule or particle of water from a groundwater system is defined as the time required for that water particle to travel from the point of recharge to a measurement point in the aquifer. Knowledge of groundwater age can be used to infer groundwater flow paths and recognize areas of groundwater recharge. An understanding of groundwater age can be used to reconstruct contaminant loading histories or explain trends in groundwater quality, and can contribute to the understanding of groundwater susceptibility to contamination. Estimates of groundwater age also can be used to constrain groundwater flow and transport models, rates of recharge, rates of groundwater movement, and biogeochemical reaction rates.

A recently released USGS report documents selected age data interpreted from measured concentrations of environmental tracers in groundwater from 1,399 USGS National Water-Quality Assessment (NAWQA) Program groundwater sites across the United States. The tracers of interest were chlorofluorocarbons (CFCs), sulfur hexafluoride (SF₆), and tritium/helium-3 (³H/³He). Tracer data compiled for this analysis primarily were from wells representing two types of NAWQA groundwater studies—Land-Use Studies (shallow wells, usually monitoring wells, in recharge areas under dominant land-use settings) and Major-Aquifer Studies (wells, usually domestic supply wells, in principal aquifers and representing the shallow, used resource). Reference wells (wells representing groundwater minimally impacted by human activities) associated with Land-Use Studies also were included. Tracer samples were collected between 1992 and 2005, although two networks sampled from 2006 to 2007 were included because of network-specific needs.

Read more about the study.

View descriptions of other Oregon Water Science Center studies.