Reprint of the Know Your Watershed series by District Manager Lacey Townsend and Watershed Coordinator April Olbrich from previous newsletters
Do you know where the six watersheds are located in Washington County?
Below is a map of Washington County with the six different watersheds numbered. Try to match up the numbered watershed with its name.
_____ Dairy-McKay Creek
_____ Gales Creek
_____ Lower Tualatin River (including Fanno Creek Watershed)
_____ Middle Tualatin
_____ Rock Creek
_____ Upper Tualatin River
Tualatin River Watershed: Lower and Upper
The Tualatin River
The 84-mile long Tualatin River drains over 900 miles of streams and a land area of 712 square miles. It runs from west to east, beginning in the Coast Range Mountains and ending in the Willamette River near West Linn. Major tributaries that drain into the Tualatin River include Scoggins, Gales, Dairy, Rock, and Fanno Creeks. There are also many minor tributaries that drain into the River.
What is a Watershed?
A watershed is the area of land where all of the water that is under it or drains off of it goes into the same place. Everyone lives in a watershed and has a significant impact on the watershed in which one lives.
The Tualatin River Watershed
The Tualatin River Watershed is 40 miles long and 25 miles wide. It contains all of Washington County and portions of Clackamas, Columbia, Multnomah, Tillamook and Yamhill counties. Located in the northwest corner of the Willamette River Basin’s land area, the watershed is bordered by the Coast Range Mountains to the west, the Tualatin Mountains to the north and east, and the Chehalem-Parrett Mountains to the south.
The basin supports a wide range of urban, agricultural, and forest activities. There are many pollution concerns throughout the basin, caused in major part by a rapid increase in population. The population is expected to increase from 455,000 in 2005 to 700,000 by 2040.
The Tualatin is “water quality limited” for several parameters, including temperature, phosphorus, ammonia, chlorophyll a, flow modification, and habitat modification. The state has developed Total Maximum Daily Loads (TMDLs) for Ammonia, Phosphorus, and Temperature to ensure water quality standards are maintained.
Many landowners choose to install conservation practices on their property to address natural resource concerns in the watershed. As of 2005, about 5,000 acres of conservation practices have been applied.
The Conservation District is paying very close attention to the Dairy-McKay watershed through 2015 as it makes up our Focus Area. Visit our Focus Area page to learn more about the watershed and this effort!
The Dairy-McKay Watershed drains 231 square miles in the northern part of the Tualatin River Watershed, in Washington county. It is the largest watershed contributing to the Tualatin River, making up nearly one-third of the Tualatin River Watershed. Three major tributaries drain the watershed: West Fork Dairy Creek, East Fork Dairy Creek, and McKay Creek. West Fork Dairy and East Fork Dairy merge north of Hillsboro to form Dairy Creek. McKay Creek joins Dairy Creek near its mouth in Hillsboro.
The northern half of the watershed is primarily dominated by forestry. Agriculture accounts for about 40 percent of the watershed area, and is found primarily within the central part of the watershed. About 5 percent of the southern part of the watershed is located within the Urban Growth Boundary.
Historically, the watershed was made up of dense forest broken by occasional prairies. The prairies were settled by pioneers near the current sites of Hillsboro and North Plains.
Dairy Creek and its tributaries provide important habitat for steelhead trout, cutthroat trout, and the non-native coho salmon. Steelhead trout are listed as threatened under the Endangered Species Act. Red-legged frog, tailed frog and Columbia torrent salamander are amphibians of concern found in the watershed.
Both Dairy Creek and McKay Creek are water quality limited for several parameters. Riparian corridors are generally narrow, and are even lacking along many stream reaches.
Gales Creek Watershed
The Gales Creek Watershed (77.9 square miles) is a primarily rural watershed, located within the western part of the Tualatin River Watershed. It lies to the east of the Coast Range Mountains, within the northwestern edge of Washington County. The watershed is divided into nine subwatersheds, with 17 tributaries flowing into the 23.5 miles long Gales Creek. The watershed’s 77.9 square miles are drained by Gales Creek, which is 23.5 miles long, flowing southeast until it enters the Tualatin River near Forest Grove.
The major land uses in the watershed include forestry, agriculture, rural residences, and rural services. Forestry is the primary land use, followed closely by agriculture. Agriculture uses include a variety of irrigated crops, large-scale non-irrigated crops, and small-scale animal operations.
- 64% privately owned (industrial forest land 26%, private agriculture/rural residential 38%)
- 28% owned and managed by the Oregon Department of Forestry (Tillamook State Forest)
- 8% owned by Forest Grove
The Gales Creek Watershed is named after Joseph Gale, a former mountain man who arrived in 1841. Gale established the first saw and grist mills in 1844,and imported the area’s first livestock (Spanish longhorn cattle and sheep).
The waters of Gales Creek have been used for agriculture, log transportation, sawmills, and drinking water since early settlement. The watershed has been significantly altered throughout history. This includes the start of industrial logging in the 1870s and creation of small diversions throughout the watershed for irrigation and domestic purposes.
Fish species found in the watershed include cutthroat trout, steelhead trout, and coho salmon. Many factors limit the fish habitat quality. Gales Creek is “water quality limited” for several parameters, including ammonia, bacteria, phosphorus, temperature, and dissolved oxygen.
The two largest land uses in the watershed, forestland and agriculture, have significant impacts on water quality within the Gales Creek Watershed. Environmental concerns associated with forestland (timber harvest and timber roads) include impact to streams by contributing sediment, reducing riparian vegetation, limiting large woody debris recruitment, and limiting shade-bearing trees. Environmental concerns associated with agriculture include stream channelization, reducing riparian vegetation, streambank erosion, and increased sediment and chemical pollution. All of these impacts have detrimental affects on water quality.
The Tualatin River Watershed Council’s (Council) Lower Gales Creek Habitat Enhancement Plan focuses on a five-mile stream reach (Stringtown Road to Iller Creek). Working with landowners, the Council and its partners want to design and implement projects to improve in-stream complexity (increasing large wood in the stream), floodplain connections (enhancing riparian areas and terracing and re-vegetating stream banks), riparian areas (through plantings) and evaluating fish barriers.
The Council, working with a private landowner, will implement a project this summer. The work includes removing a farm road from a riparian area, adding large wood structures in the riparian area that will create more pool and scour habitat, creating several ponds for amphibians, and planting 2.5 acres of the riparian area with native plants.
Several landowners throughout the watershed, with help from the SWCD and the USDA-Natural Resources Conservation Service, have installed a variety of conservation practices to address environmental concerns. These practices include changes in management strategies, riparian plantings, erosion control practices, planting cover crops, and drip irrigation.
Fanno Creek Watershed
The Tualatin River Watershed encompasses six subwatersheds, each of which is made up of even smaller watersheds. Fanno Creek, located within the Lower Tualatin Subwatershed, is the third watershed to be highlighted in our Watershed Focus series.
The Fanno Creek Watershed drains 32 square miles in the southeastern part of the Tualatin River Watershed, in both Washington and Multnomah counties. Fanno Creek begins in the Tualatin Mountains and flows southwest through the cities of Portland, Beaverton, Tigard, Durham, and unincorporated areas of Washington County. It enters the Tualatin River near Durham, about 9 miles above the Tualatin confluence with the Willamette River at West Linn. Fourteen tributaries (approximately 117 miles of streams) flow through the watershed.
The watershed is primarily urban, with 82% zoned as single-family residential and 7% parks and open space. The remaining 11% of the watershed is made up of other land uses, including commercial and multi-family residential.
One-third of the watershed is made up of impervious surface area, contributed by the many buildings, parking lots, streets and sidewalks. Despite the urbanization of the watershed, however, Fanno Creek passes through 14 parks managed by several different agencies.
The creek is named after Augustus Fanno, the first settler of European descent to inhabit the watershed. He settled and established an onion farm in 1847, near what is now Beaverton. At that time, people living within the watershed depended on logging, farming, and dairy farming for their livelihoods. At the turn of the century, the watershed became more accessible for urban development with the arrival of the Southern Pacific Railroad and the Oregon Electric Railway lines.
The extensive pavement makes storm water runoff the biggest concern in this watershed. Oil and gasoline from the road systems, as well as fertilizers and pesticides used in residential and commercial landscaping, are common pollutants entering Fanno Creek. These pollutants, along with sediment, erosion, and the lack of vegetation along the stream, limit water quality.
The upper reaches of Fanno Creek do support a limited amount of aquatic life, however, including steelhead and cutthroat trout. Approximately 100 bird species use the watershed, as well as several small-and-medium sized mammals.
McFee Creek Watershed
The McFee Creek Watershed drains over 15 square miles in the southeastern part of the Tualatin River Watershed, in Washington county. Beginning in the Chehalem Mountains, McFee Creek flows northward, draining into the Tualatin River near Scholls.
In 2005, the McFee Creek Watershed Strategic Plan was developed by a Steering Committee, organized by residents living within the watershed. The McFee Creek Steering Committee is comprised of local citizens working with public and private organizations to achieve water quality, while supporting diverse land uses.
The watershed is primarily agricultural. Agriculture uses include livestock, dry cropland, irrigated cropland, and specialty crops. Other land uses include rural residences and forestry. There are over 63 miles of roads with approximately 49 road-stream crossings.
Approximately 5 miles of stream have been identified as winter steelhead habitat by the Oregon Department of Fish and Wildlife. This is important because winter steelhead are legally designated as being threatened in Oregon. Other wildlife species in the watershed that are listed as species of concern or threatened, include Northern Red-Legged Frog, Bald eagle, and Nelson’s checker mallow.
McFee Creek is water quality limited for Dissolved Oxygen, Fecal Coliform, and Phosphorus. The Oregon Department of Agriculture has done agricultural stream monitoring from 1994 to 2006. As stated in the McFee Creek Watershed Strategic Plan, trends are as follows: temperature is slightly decreasing, dissolved oxygen is getting better, there is a slight increase in phosphorus, and ammonia has not been monitored.
Watershed (aka Basin, Drainage)
Water Quality Limited
Total Daily Maximum Load (TMDL)
Urban Growth Boundary
Species of Concern
Large Woody Debris
Pools and Scour
Incorporated and Unincorporated
Commercial Land Use
Multi-Family Residential Land Use
Residential Land Use
Storm Water Runoff