Threemile Lake (Douglas)
Reachcode: 17100207011137 | Area: 87.0 acres | Shoreline: 3.7 mi | View on Interactive Map
(From Atlas of Oregon Lakes, Johnson et al. 1985) The Threemile Lakes are a pair of long, narrow lakes in the sand dunes of the central Oregon coast and are presented here as one unit. They are named for nearby Threemile Creek which flows into the Pacific Ocean. The creek was named on the assumption that its mouth is three miles from the Umpqua River; in fact it is about four miles. This is a relatively isolated region dominated by a developed system of foredunes and active dunal ridges. As the dunes advanced inland they formed linear depressions which now contain long, narrow lakes parallel to the shoreline. The Threemile Lakes are a typical example of this mode of formation, lying in a trough between an active ridge on the west and older, stabilized dunes to the east. The surface elevation (20 feet) and maximum depth (33 feet) of the lakes suggest that the basin is a cryptodepression, a lake basin extending to below sea level.
Surface inflow is from a small, unnamed creek on the north end, which enters through a marshy area, and from two other small, intermittent streams. There is no surface outflow; seepage and evaporation account for seasonal reductions in water level. In the summer, because of the drop in water level, two separate lakes exist connected by a short, narrow channel. In some years even this channel dries up so that the lakes are completely separate. Dense brush is found around the perimeter of the lakes except at the northwest end where dunes are actively encroaching on the waterline. Although the Threemile Lakes are within the Oregon Dunes National Recreation Area, most of the terrain to the east is owned and managed by private timber interests and is covered with a second—growth Douglas fir forest. The rest of the drainage basin is under federal management.
Water transparency is above average for coastal lakes (Secchi disk depth = 13.1 ft; 4 m), suggesting low productivity, and there is no evidence of emergent macrophytes. Submerged macrophytes are apparent on the lake bottom in the shoal area, except where encroaching sand restricts their development. The lakes are exposed to strong prevailing winds and do not stratify significantly. Based on the Secchi disk readings they are classified as mesotrophic.
The Threemile Lakes contain a variety of fish species, notably cutthroat trout and yellow perch. However, due to the limited access the lakes are little visited and have remained relatively undisturbed. There are apparently no plans for further development and it is reasonable to expect that their quiet, primitive character will be retained.
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.
|-||Veronica catenata (chain speedwell)||Native||CLR|
|-||Utricularia vulgaris (common bladderwort)||Native||CLR|
|-||Ranunculus flammula (creeping buttercup)||Native||CLR|
|-||Potamogeton robbinsii (fern leaf pondweed)||Native||CLR|
|-||Myriophyllum sibiricum (northern watermilfoil)||Native||CLR|
|-||Isoetes nuttallii (Nuttall's quillwort)||Native||CLR|
|-||Eleocharis sp. (spikerush)||Native||CLR|
|-||Juncus supiniformis (spreading rush)||Native||CLR|
|-||Persicaria amphibia (water smartweed)||Native||CLR|
|-||Nuphar polysepala (yellow water-lily)||Native||CLR|