- Curry County)
(From Atlas of Oregon Lakes, Johnson et al. 1985). Garrison Lake is a shallow coastal lake located adjacent to the city of Port Orford and within its northeastern urban growth boundary. On some older maps the lake is shown as Garrison Lagoon, but the name Garrison Lake has been officially adopted. It was named for John B. Garrison, a pioneer settler who was with Captain William Tichenor when he founded the town of Port Orford in 1851. Garrison Lake is a typical sand dune lake, separated from the nearby ocean by a low ridge of shifting dunes. As with many of the coastal lakes in Oregon, it was formed when the post-glacial rise in sea level caused submergence of the lower reaches of coastal streams. In this case a small stream was unable to maintain its course across the encroaching sand dunes and the lake was separated from the ocean.
The only surface inflow to Garrison Lake from its small drainage basin is a small, intermittent stream entering at the northeast end. Surface outflow is to the southwest, where an intermittent stream follows a twisting route to the ocean a quarter of a mile distant. Generally there is no flow in this stream during the summer when lake level is low. A seasonal fluctuation in water level of Garrison Lake of about one and one-half feet is reported. The surrounding hillsides support a second-growth coniferous forest. Willows and California Madrona grow near the lake and much of the shoreline is in deep brush.
Garrison Lake is used for recreational boating, fishing, and swimming and has been an important part of the lifestyle of Port Orford residents for many years. About 85 percent of the shoreline is in private ownership and many homes have been built along the shore, especially in the last two decades. In past years the lake has yielded good catches of rainbow and cutthroat trout. It is stocked regularly and also supports some native cutthroat. However, because of the large amount of private land surrounding the lake, access is difficult and it is hard to fish. There are two access points for the general public: a gravel boat ramp maintained by Curry County on the northeast shore and a paved state ramp on the south shore. The nearest camping area is Humbug Mountain State Park, about four miles south of Port Orford.
Proximity to the ocean plays a major role in the natural thermal and chemical characteristics of Garrison Lake. Prevailing winds keep it well-mixed, preventing stratification and making the lake turbid at times. Concentrations of major ions in the water are somewhat above average for coastal lakes, reflecting its proximity to the ocean. Conductivity is also fairly high, due mostly to sodium and chloride derived from the ocean. Ecological conditions vary considerably over the course of the year. Major ion concentrations were similar in August, November, and February, but considerably lower in May. Total phosphorus and chlorophyl followed a similar pattern. During winter and late spring, concentrations are about average for coastal lakes and transparency slightly less than average. By late summer phosphorus and chlorophyl concentrations are well above average for coastal lakes, transparency is reduced, and there is a marked increase in pH.
The species of phytoplankton in Garrison Lake are somewhat unusual, and further reflect the varying ecological conditions throughout the year. In the spring Dinobryon was dominant; this alga is most often associated with lakes having low phosphorus concentrations and low trophic states. In summer Desmidium and Nitzchia were dominant; these algae are very rare (not observed in any other lake in this study) and indicate unusual conditions in the lake. 0ocystis and Sphaerocystis, also observed in summer, are more common in oligotrophic lakes than in lakes with higher trophic states. The autumn phytoplankton assemblage consists of species that are widespread in many types of lakes. It appears that Garrison Lake, a complex ecosystem, is influenced by a large variety of factors.
Garrison Lake is not unlike many in the coastal area, with sandy shores and a considerable amount of macrophytes in the shallow areas. However, in the 1960s it began to suffer from the spread of macrophytes, to the extent that swimming and fishing have been restricted. Opinions concerning the causes of the macrophyte problem vary. Certainly the natural characteristics of the lake basin are a factor. Garrison Lake consists essentially of two basins connected by a shallow channel, the north basin being the larger and deeper of the two. The south basin is nowhere more than 12 feet deep and two thirds of the entire lake is shallower than 10 feet. In addition, poor water circulation results from poor drainage into and out of the lake. Thus, the lake would be expected to support a natural abundance of rooted macrophytes. A contributing factor is the in-filling through sediment accumulated from the drainage basin, a natural process which has been accelerated by road-building activity. The rapid eutrophication of Garrison lake in recent years suggests an overriding cultural influence, and the problem is severe. An anchor pulled from the 27 foot depth at the center of the lake in summer, 1982, was covered with Elodea. Apparently, the entire bottom is covered with this weed.There is also an abundant growth of phytoplankton in the lake which, many residents believe, is due to nutrient input from the city waste treatment plant. Other human-induced possibilities for the macrophyte and algae problems are: 1) accelerated sediment and nutrient loading from poor watershed management practices; 2) water draw-down for municipal use causing a lower lake level; 3) surface runoff contributing lawn and garden fertilizer; and 4) septic tanks draining into the lake and adding nutrients.
The water quality problems in Garrison Lake are severe and complex, involving a combination of several factors, both natural and cultural. Because it is such an important resource for residents of the Port Orford area, the interest in restoration potential will continue. The Curry and Coos County Council of Governments made tentative plans a few years ago to dredge the lake in an attempt to ameliorate the weed problem, but were not able to proceed because of a lack of funding. Dredging could be a feasible restoration technique in the event that it could economically remove a sufficient amount of sediment to reach the underlying sand. A variety of other potential solutions have been suggested for use either individually or in combination (CCCOG 1982):
a. Aquatic plant harvesting and use of the material for agricultural
b. and home fertilizer which has been found to promote better growth of
c. grasses than peat moss.
d. Watershed management to reduce the sediment and nutrient input.
e. Introduction of species of fish or waterfowl that thrive on macrophytes.
f. Chemical applications and/or screening of the bottom.