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Effects of Diamond Lake Restoration on Water Quality and Algal Conditions in the North Umpqua River, Oregon

Project Chief: Chauncey Anderson

In cooperation with Douglas County, Oregon, and the U.S. Forest Service


North Umpqua River

The North Umpqua River just above Steamboat Creek. This classic Western steelhead river is characterized by clear water in a high gradient, bedrock channel with deep pools interspersed by alluvial gravels.(Photograph by Chauncey Anderson, USGS)


Diamond Lake, the headwaters of the North Umpqua River in the Oregon Cascade Range (map), was treated with the fish poison rotenone in September 2006, to kill an invasive fish, the tui chub. The chub was blamed for the disruption of the lake’s food webs, which resulted in the decimation of the lake’s economically important recreational fishery and the recurrence of potentially toxic algal blooms that had caused the lake’s closure several times in recent years. The rotenone application involved the 8-9 month drawdown of this eutrophic lake and, therefore, the increased release of nutrient-rich water into downstream reaches.

As part of the interagency response to the lake restoration project, the USGS Oregon Water Science Center conducted water quality monitoring at selected locations downstream of Diamond Lake, including the Wild and Scenic Reach of the North Umpqua River, during 2005–2007. Together with data collected previously in association with Federal Energy Regulatory Commission relicensing and other management issues, a unique, long-term data set is available that will allow the assessment of conditions in the river both prior to and following the restoration project at Diamond Lake.


1.  Evaluate the potential effects of the Diamond Lake restoration on water quality and algal conditions in the Wild and Scenic Reach and selected locations upstream of Soda Springs.

2.  Document changes in water quality and algal conditions in the Wild and Scenic Reach between 1992 and 2007, to the extent possible.

3.  Evaluate the effect on summer water quality from selected other management activities (for example, modifications of discharge releases through PacifiCorp’s FERC relicensing process) that have occurred in the basin between 1992 and 2007.

4.  Evaluate selected options for long term data collection that will allow the U.S. Forest Service and other local agencies to track the quality of the river and document significant changes resulting from management actions.


1.  Assemble a complete set of water quality data, including discrete sample analysis and discharge measurements, diel measurements of temperature, pH, and dissolved oxygen; algal species identifications and biomass; and continuous data from streamgages and water quality monitors,

2.  Complete a quality control analysis of the final data set, including: laboratory split data (see below), laboratory standard reference samples, blanks, and replicates to ascertain our ability to detect differences in nutrient concentrations over time using data from synoptic and monthly samplings

3.  Address a set of specific questions regarding the downstream effects of the Diamond Lake Restoration project and other key management questions extending through the period of data collection.


The results from this study will be directly relevant to the U.S. Forest Service, Oregon Department of Environmental Quality, Oregon Department of Fish and Wildlife, Douglas County, and other agencies involved in management of the North Umpqua River Basin. Of particular note is the fact that Lemolo Lake, into which Lake Creek discharges water from Diamond Lake, experienced a severe blue-green algae bloom in 2007, causing a lake closure to contact recreation, and tui chub have been observed and appear to be increasing in numbers. The lessons and experiences gained from the Diamond Lake Restoration project, particularly with respect to the Wild and Scenic Reach, will therefore be directly applicable to Lemolo Lake as managers decide how best to approach the water quality issues there.


Anderson, C.W., and Carpenter, K.D., 1998, Water quality and algal conditions in the North Umpqua River Basin, Oregon, 1992-95, and implications for resource management: U.S. Geological Survey Water-Resources Investigations Report 98-4125, 78 p. + plate.

Anderson, C.W., 2001, Ecological effects on streams from forest fertilization— Literature review and conceptual framework for future study in the western Cascades: U. S. Geological Survey Water-Resources Investigations Report 01–4047, 49 p.

Rinella, F.A., 1998, Major-ion, nutrient, and trace-element concentrations in the Steamboat Creek Basin, Oregon, 1996: U.S. Geological Survey Water-Resources Investigations Report 98-4105, 31 p.

Tanner, D.Q., Arnsberg, A.J., Anderson, C.W., and Carpenter, K.D., 2006, Water Quality and Algal Data for the North Umpqua River Basin, Oregon, 2005: U.S. Geological Survey Data Series 229, p.


North Umpqua River Basin Real-Time Water-Quality Monitors

August 2007 Synoptic Survey: Water Quality, Discharge, and Algal Data

Graph Data From Umpqua River Basin Water-Quality Sites


Carpenter, K.D., Anderson, C.W., and Jones, M.E., 2014, Water quality and algal conditions in the North Umpqua River, Oregon, 1995–2007, and their response to Diamond Lake restoration: U.S. Geological Survey Open-File Report 2014–1098, 89 p.

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