LAKE TAHOE

A view from the lakeside hill


Photo: Y.Watanabe  
 

A. LOCATION

• California and Nevada, USA.
• 39:5N, 120:3W; 1,897 m above sea level.

 

B. DESCRIPTION

Lake Tahoe is located on the California-Nevada border in the SSierra Nevada Mountain Range at about 1,900 m above sea level, and is surrounded by spectacular mountain peaks. The lake water is extremely clear. The climate of the lake basin is characterized by long but rather mild winters and short, dry summers. The splendid scenery around the lake attracts many visitors.
 

The drainage basin is comparatively small as compared with other lakes, with the result that the residence time of lake water is very long. Tahoe soils are derived from volcanic or granitic parent material, and are easily eroded during heavy rain. Thus surface flows from the lake's watershed carry a continuous load of nutrients and sediments to the lake. In addition, the recent and rapid increase of visitors and residents has caused some eutrophication, though the nutrient level of the lake is still quite oligotrophic. In order to avoid further environmental disruption, the bi- state Tahoe Regional Planning Agency was established in 1970, and has worked out a plan for land use, transportation, conservation, recreational development and public services. It is well known as one of the most successful environmental management and conservation efforts in the United States.
 
 

C. PHYSICAL DIMENSIONS (1, 2, 3, 4)

 

Surface area [km2]	499
Volume [km3]	156
Maximum depth [m]	505
Mean depth [m]	313
Length of shoreline [km]	120
Residence time [yr]	700
Catchment area [km2]	841

 

D. PHYSIOGRAPHIC FEATURES

D1 GEOGRAPHICAL

• Bathymetric map: Fig. NAM-02-01.
• Number of outflowing rivers and channels (name): 1 (Truckee R.).

D2 CLIMATIC (2)

• Climatic data at Tahoe City (2)

 

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann.
Mean temp. [deg C]	-2.6	-1.9	0.1	3.3	7.5	11.4	15.8	15.4	11.8	7.2	2.2	-1.1	5.8
Precipitation [mm]	157	137	97	56	25	13	6	5	13	41	79	133	762

Fig. NAM-02-01
Bathymetric map (5).

 
 

• Water temperature: Fig. NAM-02-02.

Fig. NAM-02-02
Vertical and seasonal distribution of water temperature, the centre of the lake, April 1969-February 1970 (4).

 
 

• Freezing period: None.
• Mixing type: Monomictic.

 

E. LAKE WATER QUALITY

E1 TRANSPARENCY [m](1, 3)

Surface water, 1981: 27.6.

E2 pH(1, 3)

Surface water, 1981: 7.1-8.2.

E4 DO [mg l-1](1, 3): cf. Fig. NAM-02-03.

Surface water, 1981: 7-11.

• DO percent saturation [%]

Surface water, 1984: 90-105.

Fig. NAM-02-03
Vertical distribution of DO, the centre of the lake, 1969 (4).

 
 

E6 CHLOROPHYLLL CONCENTRATION [mg l-1](1, 3)

• Chlorophyll

Surface water, 1984: 0.07-0.41.

E7 NITROGEN CONCENTRATION (1, 3)

• NO3-N: Fig. NAM-02-04 and 06.

Fig. NAM-02-04
Vertical distribution of NO3-N, the centre of the lake, July 1969-February 1970 (4).

 
 

• Total-N [micro l-1]

Surface water, 1984: 21.1.

E8 PHOSPHORUS CONCENTRATION (1, 3)

• PO4-P: Fig. NAM-02-05.

Fig. NAM-02-05
Vertical distribution of PO4-P, the centre of the lake, July 1969-February 1970 (4).

 
 

• Total-P [micro l-1]: cf Fig. NAM-02-06.

Surface water, 1984: 5.8.
• NO3: Fig. NAM-02-06.

Fig. NAM-02-06
Total-P and NO3, Tahoe Index Station, 1978 (6).

 
 

E10 PAST TRENDS (6)

• NO3-N [tons]

 

Year	Mixing interval	Depth of mixing [m]	Euphotic zone (0-105 m)	Aphotic zone (105-450 m)
1973	9 March-19 March	450	5.71	14.32
1974	2 February-4 March	450	6.20	14.12
1975	17 February-31 March	450	5.81	13.76
1976	23 March-4 April	200-250	4.29	19.94
1977	11 March-27 May	175	3.41	29.34
1978	15 March-27 March	125-250	1.87	25.67
1979	28 February-2 April	275	4.64	24.26
1980	22 January-29 May	275	1.6	12.9

 

F. BIOLOGICAL FEATURES

F1 FLORA

• Emerged macrophytes (7)

Typha latifolia, Carex rostrata, C. vesicaria, Glyceria borealis, G. elata .
• Floating macrophytes: Nymphaea polysepala (7).
• Submerged macrophytes (7)

Isoetes bolanderi, I. muricata var. hesperia, Potamogeton richardsonii, Elodea canadensis.
• Phytoplankton (4)

Melosira crenulata, Cyclotella bodanica, Navicula aurora, Fragilaria crotonensis, Asterionella formosa, Synedra ulna, Nitzschia amphibia, Staurastrum natator, Dinobryon sociale.

F2 FAUNA

• Zooplankton

Kellicottia longispina, Epischura nevadensis, Diaptomus tyrelli, Bosmina longirostris, Mysis relicta (8, 9).
• Fish: Oncorhynchus nerka, Salmo clarki (1).

F3 PRIMARY PRODUCTION RATE: Fig. NAM-02-07.

Fig. NAM-02-07
Vertical and seasonal distribution of primary production rate, the centre of the lake, April 1969-February 1970 (4).

 
 

F4 BIOMASS: Fig. NAM-02-08.

Fig. NAM-02-08
Seasonal change of phytoplankton biomass (nine stations in the littoral zone)(10).

 
 

F6 PAST TRENDS: Fig. NAM-02-09 and 10.

Fig. NAM-02-09
Trend of the population of kokanee salmon (Oncorhynchus nerka)(1).

 
 

Fig. NAM-02-10
Trend of the populations of zooplankton (6).

 
 
 

G. SOCIO-ECONOMIC CONDITIONS

G1 LAND USE IN THE CATCHMENT AREA (1)

1977

	Area[km2]	[%]
Natural landscape Woody vegetation	706.4	88.1
Agricultural land	10.1	1.3
Residential area	64.8	8.1
Others
-	Commercial area	8.7	1.1
-	Public service	11.9	1.5
Total	801.9	100.0

 

• Main types of woody vegetation (6)

Lodgepole pine plantation (Pinus contorta var. murryana); subalpine red fir forest (Abies magnifica); jeffrey pine forest (Pinus jeffreyi); mixed conifer forest; deciduous broadleaf forest (Populus tremuloides).
• Main types of herbaceous vegetation (6)

Meadow, sagebrush and alpine communities.

G3 POPULATION IN THE CATCHMENT AREA (l)

1980

	Population	Population density [km-2]	Major cities (population)
Total	124,300	93	South Lake Tahoe (50,000)

 

H. LAKE UTILIZATION

H1 LAKE UTILIZATION

Source of water, navigation and transportation, sightseeing and tourism, recreation and fisheries.

H2 THE LAKE AS WATER RESOURCE (1)

1981

	Use rate [m3 sec-1]
Domestic	115
Irrigation	N.A.

 

I. DETERIORATION OF LAKE ENVIRONMENTS AND HAZARDS

I2 TOXIC CONTAMINATION

• Present status: None.

I3 EUTROPHICATION

• Nuisance caused by eutrophication: None.

 

J. WASTEWATER TREATMENTS

J1 GENERATION OF POLLUTANTS IN THE CATCHMENT AREA

c) Limited pollution with wastewater treatment.

J3 SANITARY FACILITIES AND SEWERAGE

• Municipal wastewater treatment systems

Secondary and tertiary treatment systems: by activated sludge, ammonia stripping and charcoal adsorption.

 

M. LEGISLATIVE AND INSTITUTIONAL MEASURES FOR UPGRADING LAKE ENVIRONMENTS

M1 NATIONAL AND LOCAL LAWS CONCERNED

• Names of the laws (the year of legislation)
1. Tahoe Regional Planning Compact (1969, as amended in 1980)
• Responsible authorities
1. Tahoe Regional Planning Agency and State Governments of California and Nevada
• Main items of control
1. Water quality, air quality and land use

 

N. SOURCES OF DATA

1. Tahoe Regional Planning Agency (1982) Environmental Impact Statement for the Establishment of Environmental Threshold Carrying Capacities. 140 pp. South Lake Tahoe.
2. Tahoe Regional Planning Agency & Forest Service, U.S. Department of Agriculture (1971) Climate and Air Quality of the Lake Tahoe Region; A Guide for Planning. 30 pp. South Lake Tahoe.
3. Tahoe Regional Planning Agency & Forest Service, U.S. Department of Agriculture (1971) Limnology and Water Quality of the Lake Tahoe Region; A Guide for Planning. 13 pp. South Lake Tahoe.
4. Holm-Hansen, O., Goldman, C. R., Richards, R. & Williams, P. M. (1976) Chemical and biological characteristics of water column in Lake Tahoe. Limnol. & Oceanogr., 21 (4): 548-562.
5. Loeb, S. L. & Goldman, C. R. (1979) Water and nutrient transport via groundwater from Ward Valley into Lake Tahoe. Ibid., 24 (6): 1146-1154.
6. Goldman C. R. (1981) Lake Tahoe: two decades of changes in a nitrogen deficient oligotrophic lake. Verh. Internat. Verein Limnol., 21: 45-70.
7. Tahoe Regional Planning Agency & Forest Service, U.S. Department of Agriculture (1971) Vegetation of the Lake Tahoe Region ; A Guide for Planning. 43 pp. South Lake Tahoe.
8. Goldman, C. R., Morgan, M. D., Threlkeld, S. T. & Angeli, N. (1979) A population dynamics analysis of the cladoceran disappearance from Lake Tahoe, California-Nevada. Limnol. & Oceanogr., 24 (2): 289-297.
9. Threlkeld, S. T. (1981) The recolonization of Lake Tahoe by Bosmina longirostris: evaluating the importance of reduced Mysis relicta populations. Ibid., 26(3): 433-444.
10. Eloranta, P. V. & Loeb, S. L. (1984) Near-shore littoral phytoplankton communities in Lake Tahoe, California-Nevada. Verh. Internat. Verein Limnol., 22: 600-604.