Tahkenitch Lake (Douglas)
Reachcode: 17100207000084 | Area: 2117.9 acres | Shoreline: 48.9 mi | View on Interactive Map
(From Atlas of Oregon Lakes, Johnson et al. 1985). Tahkenitch Lake is one of the larger lakes on the Oregon coast with a surface area of 1674 acres. The name is from an Indian word that is said to mean "many arms." In fact, the shape of the lake is dendritic, or branching, a shape which reflects its origin as a sand dune-dammed water body. As with Siltcoos Lake immediately to the north and with many other lakes of the region, Tahkenitch Lake was formed as a result of fluctuating sea level during and after the Pleistocene Epoch. The coastal area was submerged during the post-glacial rise in sea level and the lower reaches of coastal streams were drowned by the rising waters. Larger rivers, the nearby Umpqua for example, now have large estuaries as a result of the inundation of their lower reaches. On the smaller streams, the outlets became very sluggish and unable to keep their mouths free from drifting sand dunes and from their own sediments. The larger coastal lakes, including Tahkenitch, have formed where sand barriers succeeded in completely blocking the former stream mouths, impounding water behind the sand dune dams. Thus, large freshwater lakes were formed at levels which are higher than today's lower sea level (Cooper 1958).
One result of the mode of formation is that the lake has an extremely long shoreline (25.5 miles) with arms extending up tributary valleys. Fivemile Creek is the major stream entering the lake and Leitel Creek is another sizeable stream entering at Mallard Arm. Several other small streams also drain into the lake. Most of the lake is shallow: the mean depth is 10.9 feet; maximum depth is 23 feet; and 36 percent of the lake is less than 10 feet deep. There are two large freshwater marshes where Fivemile and Leitel Creeks enter. Leitel Marsh extends about two miles east of the lake and Fivemile Marsh about four miles; both host a rich variety of macrophytes. Outflow from the lake is at the west end through Tahkenitch Creek, which flows less than a mile through sand dunes before discharging into the ocean. The water level elevation reportedly fluctuated as much as 12 feet annually in past years; however, this has been controlled somewhat by the construction of a low dam at the outlet in 1963 by International Paper Company. The purpose of this structure and a similar one at Siltcoos Lake is to provide a year-round supply of fresh water for the company's pulp mill at Gardiner. The dam has apparently had no adverse effect on migrating fish species. Anadromous species of fish continue to pass through the lake, spawning primarily in Fivemile and Leitel Creeks. The dam has also had the beneficial effect of raising the water level, especially during summer and fall.
Although the drainage basin of Tahkenitch Lake is almost entirely forest land, nearly half of the land bordering the lake has been logged off and is in various stages of regrowth. Douglas fir, spruce, alder, and various types of shrubs predominate. Crown Zellerbach is the principle land holder in the immediate area and some of the upper part of the drainage basin is within the Siuslaw National Forest. Nearly the entire shoreline is in private ownership, some owned by the timber company, some by small lot owners. There are many homes around the lake. Tahkenitch Lake is probably as good a warm-water fishing lake as Siltcoos Lake, but it is not as heavily used. The main catch consists of yellow perch, catfish, and bluegill. Quite a few rainbow trout and cutthroat trout are taken early in the season and both are stocked annually. It is also a very productive largemouth bass lake, with the catch lasting well into the fall. Tahkenitch is one of the few lakes to have both smallmouth and largemouth bass. A few silver salmon and steelhead are also taken each winter. A boat is necessary for fishing as the shore is too brushy for shore access. There is one resort on the lake, adjacent to U. S. Highway 101. There is also a Forest Service campground and boat ramp near the highway and a public launch provided by Crown Zellerbach.
Unfortunately, greater use of Tahkenitch Lake is restricted because of a severe macrophyte problem. In the 1930s the Brazilian Water Weed, Egeria densa, was apparently introduced intentionally into the lake, at the same time it was introduced into Siltcoos Lake. It is as abundant as ever, despite efforts of various state agencies to control it. Tahkenitch Lake was included in the Department of Environmental Quality's 1979 report on eutrophic lakes in Oregon, and it was noted that the weed problems are similar to those in adjacent Siltcoos Lake and several other large, shallow coastal lakes which have been invaded by the Brazilian Water Weed (McHugh 1979). Repeated studies of this problem have been made by a number of public agencies and academic groups; however the problem is no nearer to solution now than it was in the beginning. For example, the Oregon Department of Fish and Wildlife installed "macrophyte screens" around a fishing pier located adjacent to Highway 101 to curtail macrophyte growth and enhance fishing. However, the screens were not successful, and macrophytes are again dense near the pier. Nearly the entire bottom of the lake is covered with a dense mat of macrophytes, greatly restricting boating and swimming and presenting a nuisance to anglers. The larger lakes are extremely finefishing areas, both for warm-water fish and for trout and salmon, and would be more heavily used were it not for the weed problem. This is certainly true for Tahkenitch Lake. While the use of herbicides or weed harvesters can be used to clear small areas near resorts and similar places, semipermanent reduction of the extensive weed stands demand more general treatment. Among the possibilities are: deepening the lakes, bottom sterilization, and biological controls (McHugh 1979).
Aside from the macrophyte problem, water quality in Tahkenitch Lake is reasonably good. The lake is exposed to strong sea breezes and shows little tendency to stratify. Some weak stratification and oxygen depletion in the confined deeper areas has been observed on occasion, but the lake is usually unstratified and saturated with oxygen. Water transparency, chlorophyl, and phosphorus are about average for the coastal lakes, and indicate ecological conditions at the high end of mesotrophy. The water in the lake is low in mineral content and soft, and shows the characteristic enrichment with sodium and chloride of coastal lakes. Phytoplankton densities during summer and fall are moderate, but during the spring a diatom bloom of Asterionella formosa was observed. The species composition, together with their densities, indicate mesotrophic conditions. Most of the algae found are widespread, occurring in lakes having various trophic states; for example, Anabaena (eutrophic indicator) and Sphaerocystis (usually found in oligotrophic lakes).
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.
|-||Sparganium sp. (bur-reed)||Native||CLR|
|-||Utricularia vulgaris (common bladderwort)||Native||CLR|
|-||Elodea canadensis (common elodea, Canadian waterweed)||Native||CLR|
|-||Hippuris vulgaris (common mare's-tail)||Native||CLR|
|-||Najas flexilis (common naiad)||Native||CLR|
|-||Ceratophyllum demersum (Coontail; hornwort)||Native||CLR|
|-||Potamogeton natans (floating leaf pondweed)||Native||CLR|
|-||Potamogeton amplifolius (large-leaf pondweed)||Native||CLR|
|-||Myriophyllum sibiricum (northern watermilfoil)||Native||CLR|
|-||Callitriche hermaphroditica (northern water-starwort)||Native||CLR|
|-||Potamogeton richardsonii (Richardson's pondweed)||Native||CLR|
|-||Potamogeton pusillus (slender pondweed)||Native||CLR|
|-||Egeria densa (South American waterweed, Brazilian elodea)||Non-native ODA Class B||CLR|
|-||Nitella sp. (stonewort)||Native||CLR|
|-||Brasenia schreberi (watershield)||Native||CLR|
|-||Nuphar polysepala (yellow water-lily)||Native||CLR|
|Oct. 15, 2004||Cabomba caroliniana (fanwort, Carolina fanwort)||Non-native||IMAP|
|Aug. 5, 2004||Egeria densa (South American waterweed, Brazilian elodea)||Non-native ODA Class B||IMAP|
|July 4, 1947||Egeria densa (South American waterweed, Brazilian elodea)||Non-native ODA Class B||IMAP|
|April 7, 1947||Egeria densa (South American waterweed, Brazilian elodea)||Non-native ODA Class B||IMAP|