Sunset Lake

(
• Clatsop County
)

(From Atlas of Oregon Lakes, Johnson et al. 1985)  Sunset Lake (also known commonly as Neacoxie Lake) is one of several lakes on the Clatsop Plains on the northern Oregon coast and is similar in geomorphic origin to nearby Coffenbury and Smith Lakes. It is an interdune lake, unusually long (three miles) and narrow, and is situated between relict sand dunes that trend north and south. Seasonal variation in water level occurs in response to fluctuations in the regional water table, from about 20 feet above mean sea level in the fall to about 22 feet in the early spring. There is no surface inflow to the lake, water coming from direct precipitation and from seepage; surface outflow is through Neacoxie Creek to the south.

Farms and pastureland surround much of Sunset Lake. On the west shore is a concentration of summer homes and resorts; to the northeast is a public park and the Astoria Country Club which has a small water right for golf course irrigation. Access to the lake is convenient at several points and there are good facilities for boat launching. Recreational use is quite heavy at times, angling being the principal activity. Rainbow trout are stocked and taken quite successfully. Cutthroat trout, yellow perch, crappie and catfish are also present.

Sunset Lake is slightly deeper than other lakes in the area and will, on occasion, develop a thermal stratification in spite of exposure to the strong prevailing winds of the Oregon coast. The hypolimnion is sometimes partially depleted of oxygen. Conductivity is above average and the alkalinity is among the highest of the coastal lakes observed in this survey. The reason for the high alkalinity is not known. Lake water is slightly stained with organic matter and transparency is limited (Secchi disk depth = 3.0 feet; 0.9 meters). Most of the buildings around the lake use septic tanks for sewage disposal, which means that there may be some enrichment of algal nutrients from this source as the soils in the area are sandy and very permeable.

Coliform counts on Sunset Lake are often higher than those of most Oregon recreational lakes, but the reason is not evident. It may in part be due to drainage from farmland or from fecal matter produced by waterfowl. BOO levels are consistently low, indicating that little organic matter is entering the lake (McHugh 1972). The species of algae vary considerably at different ends of the lake (see McHugh 1972 for a detailed listing). Those in the center of the lake include some diatoms that are more typical of flowing waters (e.g. Gomphonema, Cymbella, Epithemia, and especially Rhoicosphenia). Many dense beds of macrophytes are found around the periphery of the lake. As with nearby Smith Lake, Sunset Lake might lend itself to an improvement of water quality by dredging down to the clean sand layer which underlies the accumulatedorganic matter on the bottom. The Secchi disk depth, high concentrations of algal nutrients and the chlorophyl indicate a eutrophic state for Sunset Lake.