Timothy Lake (Clackamas)

Reachcode: 17090011000850 | Area: 1399.7 acres | Shoreline: 11.6 mi | View on Interactive Map

(From Atlas of Oregon Lakes, Johnson et al. 1985). Timothy Lake is an artificial lake that was formed when Portland General Electric dammed the Oak Grove Fork of the Clackamas River in 1956 for the generation of hydroelectric power. The resulting impoundment flooded Timothy Meadows, an area that for many years had been a favorite of sheepherders for summer grazing. The name of the meadow was derived from their practice of spreading Timothy grass seed to supplement the natural grasses. The reservoir project was many years in making. In 1911, permits to build power generation facilities near the present dam site (and at several other locations on the Clackamas River) were issued to the Southern Pacific Railroad in anticipation of electrifying their lines in the Willamette Valley. These rights were soon purchased by P.G.E. However, due to the rough terrain and lack of access roads in the area, only preliminary surveys for development were made prior to 1953. In that year the Federal Power Commission approved the P.G.E. plan to dam the river to provide a reserve of water to increase the power generation capabilities of hydroplants situated farther downstream on the Clackamas. Timber was cleared from the site, service roads were constructed, and the dam was completed in January 1956. It is an earthfill structure, 110 feet in height and 740 feet long. The shape of the basin is more circular than is common for reservoirs, as it gives the appearance of a natural lake when full. At full pool Timothy Lake has a surface area of nearly 1300 acres and holds over 57,000 acre-feet of water.

Sheepherders no longer use the site of Timothy Meadows, but the lake has become the destination for a great number of recreationists. Access is by paved roads, and there are five Forest Service campgrounds along the shoreline. One of these, Meditation Point, is a wilderness campsite on the northwest side of the lake that can be reached only by boat or foot trail. Excellent boat launching facilities are also available, but there is a 10 mph speed limit for boats. Timothy Lake is a popular fishing lake, perhaps more because of its aesthetic appeal rather than for being a good producer. Rainbow trout and cutthroat trout are stocked regularly, and there is sufficient biological productivity in the lake to support a natural reproduction of kokanee and brook trout. Early season fishing is generally slow, and the lake produces best in the summer and fall. Fly angling near the mouths of the tributaries is excellent in late season. Although Timothy Lake is a reservoir, there are no irrigation withdrawals and fluctuations in water level are small compared to those undergone by most reservoirs. Thus, it is available for recreation throughout the year, except when access is blocked by snow. Heavy use has led to management and environmental problems at the lake: overuse and overcrowding, forest fires from campfires, law enforcement problems, destruction of vegetation, and erosion from overuse. Forest Service management practices are designed to control erosion and to rehabilitate overused areas.

The 52 square mile drainage basin to Timothy Lake is volcanic terrain of moderate relief. It is covered with a thick coniferous forest, although there are a number of large clear-cut areas that have been reseeded with Douglas fir. Land is also leased to ranchers for cattle and sheep grazing. A few small lakes are within the drainage basin, including Little Crater Lake, a geologic curiosity formed by the force of an artesian spring washing away the overlying siltstone.

The concentrations of major ions in Timothy Lake are average for reservoirs in the Willamette drainage basin. The concentrations of phosphorus and chlorophyl and the water transparency indicate that the lake is mesotrophic. The species of phytoplankton observed in the lake are predominantly diatoms characteristic of mesotrophic lakes (Asterionella, Fragilaria, and Synedra); the chrysophyte Dinobryon is also common. Macrophytes are scarce. The lake develops a distinct thermal stratification during summer months, but is usually well oxygenated throughout the year, although periods of oxygen depletion have been observed. The bottom of the lake is covered with sunken logs and branches left from the construction period, and their decay may contribute to occasional oxygen depletion in the bottom water. These logs probably also contribute to the abundance of crayfish ("crawdads") that occur in the lake by providing a suitable habitat for these crustaceans. It is not unusual for reservoirs to be more productive for several years after flooding than they are in later years, when nutrients from submerged soils and organic debris have been used up or sealed off by silt. Timothy Lake may yet experience this transition. There is no evidence that nutrients are entering the lake from camp areas (McHugh 1972), and there is a good flow-through of water all year. Human activity has apparently little influence on water quality.


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.

Download the complete dataset as a CSV

Date Species Status Source
Aug. 20, 2014 Typha latifolia (common cat-tail) Native CLR
Aug. 20, 2014 Potamogeton gramineus (grass-leaved pondweed) Native CLR
Aug. 20, 2014 Bryophyte, aquatic (moss or liverwort) Native CLR
Aug. 20, 2014 Limosella aquatica (mudwort) Native CLR
Aug. 20, 2014 Sparganium angustifolium (narrowleaf bur-reed) Native CLR
Aug. 20, 2014 Eleocharis acicularis (needle spikerush) Native CLR
Aug. 20, 2014 Callitriche hermaphroditica (northern water-starwort) Native CLR
Aug. 20, 2014 Potamogeton alpinus (red pondweed) Native CLR
Aug. 20, 2014 Potamogeton pusillus (slender pondweed) Native CLR
Aug. 20, 2014 Nitella sp. (stonewort) Native CLR
Aug. 20, 2014 Ranunculus aquatilis (water-buttercup) Native CLR
Aug. 20, 2014 Schoenoplectus subterminalis (water clubrush) Native CLR
Aug. 20, 2014 Persicaria amphibia (water smartweed) Native CLR
Aug. 20, 2014 Utricularia ochroleuca ( yellowishwhite bladderwort) Native CLR
Sept. 12, 2011 Fontinalis sp. (aquatic moss, fontinalis moss) Native CLR
Sept. 12, 2011 Ranunculus flammula (creeping buttercup) Native CLR
Sept. 12, 2011 Sparganium angustifolium (narrowleaf bur-reed) Native CLR
Sept. 12, 2011 Eleocharis acicularis (needle spikerush) Native CLR
Sept. 12, 2011 Callitriche hermaphroditica (northern water-starwort) Native CLR
Sept. 12, 2011 Potamogeton alpinus (red pondweed) Native CLR
Sept. 12, 2011 Potamogeton pusillus (slender pondweed) Native CLR
Sept. 12, 2011 Nitella sp. (stonewort) Native CLR
Sept. 12, 2011 Ranunculus aquatilis (water-buttercup) Native CLR
Sept. 12, 2011 Persicaria amphibia (water smartweed) Native CLR
Aug. 17, 2004 Utricularia vulgaris ssp. macrorhiza (common bladderwort) Native CLR
Aug. 17, 2004 Ranunculus flammula (creeping buttercup) Native CLR
Aug. 17, 2004 Callitriche heterophylla (different-leaved water-starwort) Native CLR
Aug. 17, 2004 Potamogeton natans (floating leaf pondweed) Native CLR
Aug. 17, 2004 Sparganium angustifolium (narrowleaf bur-reed) Native CLR
Aug. 17, 2004 Potamogeton alpinus (red pondweed) Native CLR
Aug. 17, 2004 Potamogeton pusillus (slender pondweed) Native CLR
Aug. 17, 2004 Nitella sp. (stonewort) Native CLR
Aug. 17, 2004 Schoenoplectus subterminalis (water clubrush) Native CLR
No photos available.

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