Crystal Lake Watershed

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The Crystal Lake basin (37°35'36"N, 119°01'05"W in the eastern Sierra Nevada is located about 10 km southwest of the town of Mammoth Lakes. Acid deposition studies were initiated in 1986. The lake has an area of 5.0 ha and volume of 324,000 m3. Typically, one to two meters of ice cover the lake for about 6 months of the year, displacing about 15-30 % of the lake's volume. Crystal Lake is usually ice-free by the end of June.

Crystal Lake has a maximum depth of 14 meters and mean depth 6.5 meters. The lake is dimictic, meaning its waters thoroughly mix twice a year. These mixing events occur in the spring during the breakdown of ice cover and during the autumn. Maximum summertime surface temperatures in the lake ranged from 12 to 15 °C. Surface waters of the lake were well oxygenated (dissolved oxygen > 7 mg L-1), however, dissolved oxygen concentrations of less than 5 mg L-1 in the hypolimnion (i.e., waters below thermocline) were common during the winter months.
The gauged watershed was 135 ha and has a vertical relief of 293 meters. The elevation of the outlet to the gauged catchment is 2,951 meters. The basin has a north-facing aspect and is sparsely forested for about half its area with a mixture of Whitebark and Lodgepole pine. Much of the runoff from the catchment flows through an extensive meadow complex (heather, grasses, sedges and other shrubs) located along the south shore of the lake.

The eastern and southern portions of the Crystal Lake basin are dominated by a granitic dome and extensive talus. These rocks range in composition from granodiorite to alaskite with an average composition of mafic quartz monzonite. The rocks are generally coarse-grained and commonly porphyritic with phenocrysts of potassium feldspar. The remaining basin is dominated by bedrock and soils of volcanic origin. The rocks are a series of inter-bedded andesitic flows, cinders and rubble. The flow rock is commonly vesicular and essentially, nonporphyritic. The soils are classified as Volcanic Brown Soils and occur in various assemblages of rock, scree and talus. Soils in the inlet meadow are classified as Volcanic Wet Meadow. The typical Alpine Brown Soils found at most of the other catchments we studied were not found in the Crystal Lake watershed. Compared to others, the Crystal Lake watershed has a high percentage of soil cover and vegetation.

During snowmelt three major runoff channels were identified. Inflow #1 and the Main Inflow drain the eastern and southern portions of the basin. A smaller channel, Inflow #2, drains the western region of the watershed. These inflow and outflow streams are ephemeral and flow only during snowmelt or shortly after autumn precipitation; during the winter outflow is usually absent. Groundwater discharge comprises a substantial fraction of the annual loss of water from the catchment. Crystal Lake contains brook and rainbow trout.