Photo of Zosel Dam

Water level lowered at Osoyoos Lake for the winter - Ecology News Release - November 5, 2014

Help for thousands of salmon on incredible journey from Oregon to Canada - ECOconnect Blog July 28, 2014

Lake Osoyoos rises as runoff increases Washington operations help maintain lake levels for many uses - Ecology News Release May 29, 2014

Streamflow and Weather Data Sources

USGS Washington Water Science Center 

Water Office Canada Real-time Hydrometric Data

National Weather Service

Osoyoos Lake International Water Control Structure - Zosel Dam

Location:  South end of Osoyoos Lake in Oroville, WA

Owner:  Washington State Department of Ecology

Project Description:  The state of Washington Department of Ecology, under authority of Chapter 43.21A RCW, specifically 43.21A.450, owns, operates, and maintains the Osoyoos Lake International Water Control Structure - Zosel Dam.  The project, on the Okanogan River, consists of several elements located in different areas:

  1. Zosel Dam;
  2. dredged Okanogan River channel; and
  3. bank improvements at the Osoyoos Lake outlet.

The project was planned, funded, designed, and constructed in partnership with the British Columbia Ministry of Environment.  Acres International Limited of Vancouver, British Columbia, was the design and construction supervising consultant for the project.  Rognlins Inc. of Aberdeen, Washington, was the construction contractor for the project.  Operation and routine maintenance of the project is conducted under the direction of the Department of Ecology through agreements executed with public entities (ie. current agreement for operation and maintenance is with the Oroville-Tonasket Irrigation District).  The Zosel Dam is governed by United States federal law, Washington state law, and the 1909 Boundary Waters Treaty (Canada-United States of America).

Construction of Zosel Dam was completed in April 1987 on the Okanogan River at Oroville, Washington.  The site of the new dam is two miles downstream from the Osoyoos Lake outlet and nine miles south of the United States/Canadian border.  The structure was built to replace the original Zosel Dam which had been built of wood and concrete in 1927 to form a log storage pond for the adjacent Zosel Lumber Company mill. 

To improve channel capacity, dredging was completed upstream from the new dam.  Sand bars that partially blocked the channel at the Osoyoos Lake outlet were removed.  Also, sedimentation buildup at the confluence of Tonasket Creek with the Okanogan River was dredged.  Channel improvements were completed in early 1988.

Improvements were also made at the Osoyoos Lake State Park.  A sheet pile wall was installed along 600 feet of the west bank of the state park to improve bank stability along the Osoyoos Lake outlet.  A new boat launch, sidewalk, handrail, and rockfill-groyne beach were included in the project.

News Archive

Ecology makes seasonal water level changes at Osoyoos Lake - Ecology News Release September 19, 2013

Water levels rise at Lake Osoyoos as temps rise - Ecology News Release May 7, 2013

IJC issues Order for future management of Osoyoos Lake water levels International Joint Commission (IJC) January 31, 2013

U.S., Canada, Washington State agree to new cross-border lake operations  - Ecology News Release January 14, 2013

Ecology makes seasonal water level changes at Osoyoos Lake - Ecology News Release November 8, 2012

Water Levels are rising at Lake Osoyoos - Ecology News Release May 24, 2011


Al Josephy
Department of Ecology - WR
Phone: 360 407-6456