Blue Lake (Multnomah County) (Multnomah)

Reachcode: 17090012000361 | Area: 66.0 acres | Shoreline: 2.0 mi | View on Interactive Map


(From the Atlas of Oregon Lakes, Johnson et al. 1985).  Blue Lake is a 61 acre natural lake in east Multnomah County that lies parallel to the Columbia River and about 1000 feet south of it. It is a floodplain lake and was formerly connected at high water with the Columbia River, at which time river water ran through the lake into the Columbia Slough. A dike (along which Marine Drive runs) now extends along the south shore of the Columbia, blocking any surface connection with the river. Water flows into the lake primarily from seeps and springs, with the quantity influenced by the changing height of the river. No other inflows exist, except occasional runoff during periods of heavy rains. When the water level of the Columbia River drops, some water loss occurs thorough the lake bottom sediments. In early summer, when the river rises, low-lying lands along the north shore of the lake become soggy and water-soaked, and the level of the lake also rises, greatly increasing the outflow which runs eastward through a short creek into a drainage ditch along the Columbia dike. From here it is pumped back over the dike into the Columbia. The dike itself is of rock and earth construction and quite impermeable; but it lies on a sand base, through which Columbia River water seeps. During high water the pressure from the river side increases the rate of seepage through the sandy substrate. The lake's proximity to metropolitan Portland and its accessibility have made it an important recreational resource for the area. Boating, water-skiing, swimming, fishing, and picnicking have been the most popular recreational activities. The north shore of the lake is part of Blue Lake Park, operated and owned by Multnomah County. The south shore is privately owned and lined with permanent residences. Because of intensive use by lakeside residents and park visitors, Blue Lake water quality has been of concern to Multnomah County and the Oregon Department of Environmental Quality. Many studies have focused on the problems of Blue Lake (such as the presence of nuisance macrophytes and increased turbidity), and how to manage the lake to maintain water quality standards that would ensure safe and enjoyable recreational use. 

Blue Lake supports a wide variety of plant and animal life. The morphometry of the lake (its shallow depth) and the natural nutrient input from rich lake bottom sediments and groundwater provide ideal conditions for high plant productivity. During the summer months, extensive macrophyte growth, dominated by Eurasian water milfoil (Myriophyllum spicatum) occurs along the shallow west, north, and east shores of the lake to a depth of 10 feet. The south shore, however, is steeper and does not have an extensive growth of macrophytes. Transparency of the water is decreased during the summer months due to an abundance of microscopic planktonic algal growth dominated by diatoms and blue-green algae. Generally, the more algae present in the lake, the more turbid and green it becomes. Although the plant productivity impairs swimming activities, it has provided food and habitat for the resident zooplankton, benthic invertebrates, and fish. Benthic invertebrates feed on organic detritus and phytoplankton and are an important food source for fish. Fish studies have indicated that black crappie, bluegill, largemouth bass, carp, and brown bullhead are the major components of the fish population. The bottom muck sediments support benthic organisms tolerant of organically rich, low oxygen conditions. A total of seventeen benthic invertebrate taxa were identified, with crawfish and naiads (freshwater mussels) being the most common organisms observed (BEAK 1983). Densities of bacteria, another important biological component in Blue Lake, do not exceed state water quality standards for water contact recreation. 

The values of physical and chemical water quality parameters, such as temperature, dissolved oxygen, and nutrient concentrations, change seasonally in Blue Lake. Although the lake is relatively shallow, typical thermal stratification occurs during the spring and summer months. On a given summer day, surface temperatures may reach 77 degrees Fahrenheit (25 degrees Celsius) above the thermocline, and be reduced to 61 degrees Fahrenheit (16 degrees Celsius) at the bottom. As thermal stratification occurs and water temperatures increase, the dissolved oxygen levels decrease in the hypolimnion. Values may vary from 10.8 mg/l at the surface to 0.5 mg/l at the bottom, causing a near anoxic zone to form. This nearly anoxic zone remains until fall turnover, when winds and cold weather cause the lake to mix and re-oxygenate. The transparency of the water, measured by a Secchi disk, varied from 2.6 feet (0.8 meters) during summer algal blooms, to 13.0 feet (4.0 meters) during periods of low algal growth (BEAK 1983). Nutrients in the Blue Lake water are important in controlling the biological productivity of the lake. Sources of phosphorus, one of the more important nutrients and often the most limited in supply, include rainwater, groundwater, surface runoff, and anoxic sediments. Phosphorus concentrations in Blue Lake range from 0.04 to 0.6 mg/l which in conjunction with other indicators, classifies the lake as eutrophic. 

Historically, Blue Lake has been used recreationally since the early 1800 s by the Nechockee Indians. Lakewide habitation and more intensive use of the lake has occurred since the 1930s when Blue Lake Park was developed by private residents. Multnomah County purchased the park along the north shore in 1960 and has maintained the recreational facility, renewing docks and picnic areas, and building a public swim center. Peak use occurred in 1974 when 666,000 visitors participated in recreational fishing and swimming. However, swim center fees imposed in 1975, followed by closure of the lake to swimming in 1976 due to high turbidity and macrophyte growth, caused a decline in park use since then. Through efforts and funds from Multnomah County and Environmental Protection Agency, the water quality problems were studied and a rehabilitation and management plan was developed in 1982 (BEAK 1983). Control of macrophyte growth has been attempted using a variety of strategies. In the late 1960s, harvesting failed to reduce or control the macrophytes. During the winter of 1981-82, the lake level was lowered by 8 feet to expose the macrophytes to freezing temperatures and ideally kill the roots and prevent growth the following spring. The drawdown was successful and a significant decrease in macrophyte growth resulted in the summer of 1982. In addition, macrophyte growth was controlled by the application of the herbicide 2,4-D. The reduction of the macrophytes allowed the swim center to re-open, and swimming was permitted once again during the summer of 1983. Dilution water will probably be pumped into Blue Lake beginning in 1984. This may eventually increase water transparency and control nuisance algal blooms. 


Printable Lake Map
No mussel data available.

The list of plants below includes results of aquatic plant surveys conducted by the Center for Lakes and Reservoirs as well as aquatic invasive plant species detections that have been reported to iMap Invasives: an online, GIS-based invasive species reporting and querying tool.

Plants listed in the table below are categorized as native to Oregon, on the Oregon Department of Agriculture’s (ODA’s) Noxious Weed List, on the Federal Noxious Weed List, or non-native but not listed as noxious. Federal Noxious Weed List plants are plants determined by USDA to be serious threats to U.S. agriculture, irrigation, navigation, public health or the environment (7 C.F.R. 360.200). The ODA Noxious Weed categories are:

ODA Class A - weeds either unknown or with small enough infestations to make eradication or containment possible; targeted for eradication or intensive control.

ODA Class B - regionally abundant weeds (may have limited distribution in some counties); targeted for local/regional control on case-by-case basis.

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Date Species Status Source
Sept. 15, 2003 Elodea canadensis (common elodea, Canadian waterweed) Native CLR
Sept. 15, 2003 Potamogeton crispus (curly leaf pondweed) Non-native CLR
Sept. 15, 2003 Nymphaea odorata (fragrant waterlily) Non-native CLR
Sept. 15, 2003 Potamogeton foliosus (leafy pondweed) Native CLR
Sept. 15, 2003 Chara sp. (muskwort) Native CLR
Sept. 15, 2003 Nitella sp. (stonewort) Native CLR
July 24, 2003 Elodea canadensis (common elodea, Canadian waterweed) Native CLR
July 24, 2003 Potamogeton crispus (curly leaf pondweed) Non-native CLR
July 24, 2003 Myriophyllum spicatum (Eurasian watermilfoil) Non-native ODA Class B CLR
July 24, 2003 Nymphaea odorata (fragrant waterlily) Non-native CLR
July 24, 2003 Potamogeton foliosus (leafy pondweed) Native CLR
Sept. 5, 1981 Myriophyllum spicatum (Eurasian watermilfoil) Non-native ODA Class B IMAP
Aug. 14, 1981 Myriophyllum spicatum (Eurasian watermilfoil) Non-native ODA Class B IMAP
Aug. 7, 1981 Myriophyllum spicatum (Eurasian watermilfoil) Non-native ODA Class B IMAP