Oregon Lake Inventory:
Munsel Lake, Lane County, Oregon

Introduction

Munsel Lake is the last in a chain of four Oregon coast lakes that lie on the North Florence dunal aquifer (figure 1). The aquifer has been designated a "sole source aquifer" by the Environmental Protection Agency. The EPA defines a sole source aquifer as "an aquifer that supplies at least 50% of the drinking water consumed in the area overlying the aquifer. These areas have no alternative drinking water sources(s) which could physically, legally, and economically supply all those who depend upon the aquifer for drinking water." Unlike the other lakes in the chain; Collard, Clear, and Ackerly; Munsel Lake also serves as an important recreational use area for boating, swimming, and fishing. Native cutthroat trout, stocked rainbow trout, largemouth bass, yellow perch, and bluegill are recreational species that inhabit the lake.

Figure 1.

The lake, bordering sand dunes, and underlying aquifer have a common geologic origin that is typical of the Oregon coast. The dunes in this area formed through an accumulation of wind blown sand on marine terrace that had been warped below sea level. Higher sections of the terrace remain 50 to 150 feet above sea level and can be seen to the north near Newport and to the south near Bandon and Port Orford. The dune sheet that covers the terrace near Florence is permeated with water and forms the North Florence dunal aquifer. The sheet is as much as five miles wide. The lake lies in a trough between the buildup of the dune sheet to the west and the bedrock of the Coast Range foothills to the east.

Munsel Lake is supplied with water from both the aquifer and surface runoff. The relative importance of the aquifer is illustrated by the lack of substantial surface drainage despite an average annual precipitation of 79 inches. The primary surface drainage feature for Munsel Lake originates at the head of the chain in Collard Lake, flows through Clear and Ackerly Lakes, and into Munsel Lake via Clear Creek. Munsel Creek drains the lake. Seasonally, surface streams do not flow out of Clear and Munsel Lakes. Within a mile downstream of Munsel Lake, however, Munsel Creek gathers groundwater discharge and flows year round. The surface system eventually flows into the Siuslaw River and the Pacific Ocean. A generalized groundwater flow path is included in figure 2.

Figure 2.

Watershed Characteristics

Munsel Lake's watershed is composed forest, lakes, sand dunes, and residential areas (table 1). Munsel Lake covers 10% of its watershed while Collard, Clear, and Ackerly Lakes comprise 23%. A mixture of forest and sand dunes lie to the west of the lakes while forests cover foothills of the Coast Range to the west. Slopes are steep on the forested foothills and on the edges of the dunes. Elevation ranges from 27 meters above sea level at the outflow to 153 meters in the eastern hills. Forests consist of second growth conifer and hardwood species. Residential areas are present on the north and west shores of Munsel Lake and the East shore of Collard Lake. Roads are concentrated around those areas.

Table 1.

Morphometry

Munsel Lake is deeper than most other coastal lakes with a maximum depth of 23.9 meters. The north, east, and south shores of the lake abut the foothills of the Coast Range and are steep both above and below the water surface. The west end of the lake has a gently sloping bottom covered with sand and macrophyte beds. A bathymetric map of Munsel Lake is provided in Figure 3.

Figure 3.

Water Quality

Several water quality parameters were measured in the Munsel Lake during the summer of 2001. A summary is provided in table 2. The lake’s trophic state based on Secchi disc depth, chlorophyll a concentration, and total phosphorus concentration ranged from index values of 35 to 66. The highest value, well within the eutrophic range, was calculated from chlorophyll concentration in the midst of an algal bloom in April. The other trophic state values fall within the mesotrophic range. These values are slightly higher than those calculated from historical data collected by Portland State University and Oregon Department of Environmental Quality (Johnson et al. 1985). A plot of trophic state index values based on these and 2001 data is provided in figure 4.

Table 2.

Figure 4.

Munsel Lake was thermally stratified during visits in July and September at depth of 6.0 and 6.9 meters respectively. Vertical profiles of temperature and other data collected with a water quality probe are plotted below. The deepest portion of the hypolimnion was anoxic during the July visit and most of the hypolimnion was anoxic during the September visit. This extensive anoxic area may be indicative of excessive nutrient loading to the lake.

Macrophyte beds are most extensive in the shallow north and south ends of the lake. The sand, clay and mud sediments in these areas support sparse stands of the floating leaf species Brasenia schreberi, Nymphaea odorata, Potomogeton amplifolius, and Potomogeton gramineus. Submergent vegetation present includes Najas spp., Isoetes spp., and Chara spp.

The shallow west end of the lake is covered with floating leaf macrophyte species including Brasenia schreberi, Nympaea odorata, Potomogeton amplifolius, and Potomogeton gramineus. Submerged species include Isoetes spp., Chara spp., and Najas spp.

Munsel Lake, 2001 Data

APRIL 17

JULY 18

SEPT. 17

Resources

In Preparation