LAKE MENDOTA

A view from the campus of the University of Wisconsin


Photo: Y.Kada  
 
 

A. LOCATION

  • Wisconsin, USA.
  • 43:6N, 89:5W; 850 m above sea level.
 

B. DESCRIPTION

Lake Mendota is located approximately 120 km west from Milwaukee, a city on the western shore of Lake Michigan. Although the lake is comparatively small (surface area 40 km2) and shallow (mean depth 12.2 m), it is significant as a birthplace of modern limnology and an early instance of artificially accelerated eutrophication.
The lake has a freezing period of about three and a half months annually, and the concentration of dissolved oxygen in the water is generally high in the epiliminion throughout the year, though it falls to 1-2 mg/l in the bottom water during the summer.
Owing to the influx of domestic wastewater, the lake has suffered from eutrophication since the beginning of this century. From 1912 to 1958, copper sulphate was applied over the lake to reduce the overgrowth of algae. The algal bloom was effectively suppressed but the lake became polluted with copper, which still remains accumulated in the bottom sediments as insoluble copper carbonate.
The diversion project for wastewater is particularly noteworthy in the lake's water treatment plan. When the main lake became heavily eutrophicated, inflowing wastewater was diverted to the three small lakes downstream, but these also became eutrophicated over time. Therefore, the wastewater flowing into the four lakes was collectively diverted to the Yahara River to cope with the situation. The history of wastewater treatment in L. Mendota and the nearby city of Madison tells of a bitter struggle for an effective control of eutrophication (Q).

C. PHYSICAL DIMENSIONS (1, 2)

     
    Surface area [km2] 39
    Volume [km3] 0.481
    Maximum depth [m] 25
    Mean depth [m] 12.2
    Length of shoreline [km] 35.3
    Residence time [yr] 3.1-8.8
    Catchment area [km2] 522
     
 

D. PHYSIOGRAPHIC FEATURES

D1 GEOGRAPHICAL

  • Bathymetric map: Fig. NAM-0l-0l (8).
  • Names of main islands: None.
  • Number of outflowing rivers and channels (name): 1 (Yahara R.).

D2 CLIMATIC (3, 4)

  • Climatic data at Dane County Regional Airport*, 1943-1982
     
    Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann.
    Mean temp. [deg C] -8.6 -6.2 -0.1 7.8 14.0 19.3 21.9 20.8 15.9 10.2 1.9 -5.2 7.7
    Precipitation [mm] 31 26 52 74 84 104 95 91 80 53 50 39 779
    * Circa 9 km east of the centre of the lake.
  • Number of hours of bright sunshine (1947-1982): 2,500 hr yr-1.
  • Solar radiation (1951-1975): 13.5 MJ m-2 day-1.
    Fig. NAM-01-01
    Bathymetric map (8).
 
 
  • Water temperature
    Fig. NAM-01-02
    Seasonal and vertical distribution of water temperature [deg C], 1976 (1).
 
 
  • Freezing period (1852-1983): 20 December-15 April.
  • Mixing type: Dimictic.
 

E. LAKE WATER QUALITY

E1 TRANSPARENCY: Fig. NAM-01-03.

    Fig. NAM-01-03
    Seasonal changes of transparency (1).
 
 

E3 SS [mg l-1](5)

The outlet on southeast side, 1976-1977: 1.9 (0.5-6.8).

E4 DO

    Fig. NAM-01-04
    Seasonal and vertical distribution of DO [mg l-1], 1976 (1).
 
 

E5 COD [mg l-1](5)

The outlet on southeast side, 1976-1977: 21 (1-43).

E6 CHLOROPHYLL CONCENTRATION

    Fig. NAM-01-05
    Seasonal change of chlorophyll a [micro l-1], 0-2 m (1).
 
 

E7 NITROGEN CONCENTRATION

    Fig. NAM-01-06
    Seasonal change of nitrogen concentration [mg l-1], 1976 (1).
 
 

E8 PHOSPHORUS CONCENTRATION

    Fig. NAM-01-07
    Seasonal change of total and inorganic phosphorus concentration [mg l-1], 1976 (1).
 
 

E9 CHLORIDE CONCENTRATION

    Fig. NAM-01-08
    Past trends of chloride concentration [mg l-1](9).
 
 
 

F. BIOLOGICAL FEATURES

F1 FLORA

  • Phytoplankton (1, 6, 7)

    • Aphanizomenon, Stephanodiscus, Cryptomonas, Fragilaria, Anabaena, Microcystis.

F2 FAUNA

  • Zooplankton (1)

    • Asplanchna sp., Bosmina longirostris, Brachyonus sp., Ceriodaphnia sp., Chydorus sphaericus, Daphnia galeata mendotae, D. parvula, D. pulex, D. retrocurva, Diacyclops bicuspidatus thomasii, Diaphanosoma leuchtenbergianum, Filinia sp., Keratella cochlearis, K. quadrata, Polyarthra sp., Trichocerca sp.
  • Benthos (8)

    • Limnodrilus, Tubifex, Pisidium, Chironomus, Corethera punctipennis, Protenthes.
  • Fish (1)

    • Roccus chrysops, Lepomis macrochirus, Perca flavescens, Esox luis, Amoloplites rupestris, Micropterus colomieui, M. salmoides, Pomoxis nigromaculatus.

F3 PRIMARY PRODUCTION RATE: Fig. NAM-01-09.

    Fig. NAM-01-09
    Algal primary production rate [g C m-2 day-1], 1980 (7).
 
 

F4 BIOMASS

    Fig. NAM-01-10
    Biomass of phytoplankton, zooplankton and bacterioplankton, 1980 (7).
 
 

F6 PAST TRENDS: Fig. NAM-01-11.

    Fig. NAM-01-11
    Past trend of total zooplankton biomass (10).
 
 
  • Past trend of the size of Perca flavescens (11)
     
    Year 1916 1931 1932 1939 1943 1946 1948
    No. of fish in sample 169 261 51 25 297 375 210
    Average total length [mm] 162 198 180 188 214 220 243
    Average weight [g] 50 84 76 86 128 137 180
     
 

G. SOCIO-ECONOMIC CONDITIONS (Q)

G1 LAND USE IN THE CATCHMENT AREA

     
    1975
    Area [km2] [%]
    Natural landscape
    - Woody vegetation 40 7.2
    - Swamp 24 4.3
    Agricultural land 430 76.9
    Residential area 65 11.6
    Total 559 100.0
     

G2 INDUSTRIES IN THE CATCHMENT AREA AND THE LAKE

  • Main products or major industries

    • Agriculture: Dairy farming. Manufacturing: Electrical machinery, agricultural machinery, fertilizer and foods (dairy products).

G3 POPULATION IN THE CATCHMENT AREA

  • Population in the catchment area: N.A.
  • Main cities: Madison (population 170,600 in 1980)

    • Not all the city area is included in the catchment area.
 

H. LAKE UTILIZATION

H1 LAKE UTILIZATION (Q)

Sightseeing, tourism and recreation (swimming, sport-fishing).

I. DETERIORATION OF LAKE ENVIRONMENTS AND HAZARDS

I3 EUTROPHICATION

  • Nitrogen and phosphorus loadings to the lake
1976-1977 Phosphorus [kg yr-1](12)
     
    1976 1977
    Source Total P Soluble P Total P Soluble P
    Baseflow 4.500 2.600 3.700 2.300
    Precipitation 700 550 1.000 790
    Dry fallout 2.400 1,000 2.400 1.000
    Groundwater seepage 120 120 160 160
    Rural runoff
    - Monitored (397 km2) 24.200 11.700 8.200 4.900
    - Unmonitored (113 km2) 6.900 3.300 2.300 1.400
    Urban (38.6 km2) 4.200 2.100 5.100 2.500
    Total
    - kg 43.000 21.000 23.000 13.000
    - g/m2 of lake surface/yr 1.1 0.53 0.58 0.33
    - g/m3 of lake volume/yr 0.090 0.043 0.048 0.027
    Values are in kilograms for the whole lake. The urban loading does not include about 21.5 km2 of developed area in villages and cities in the monitored rural area.
Nitrogen [kg yr-1](12, 13)
     
    1976 1977
    Source Total Nitrogen Inorganic Nitrogen Total Nitrogen Inorganic Nitrogen
    Baseflow 180.000 150.000 140.000 120,000
    Rural runoff 160,000 86.000 48.000 23,000
    Urban runoff 20.000 5.000 26.000 6.000
    (Others)* (210.000) (130,000) (210.000) (130.000)
    Total (570.000) (370,000) (420,000) (280.000)
    * Includes precipitation, dry fallout, groundwater and nitrogen fixation estimates. Values in parentheses are estimates.
 

N. SOURCES OF DATA

  1. Questionnaire filled by Prof. M. S. Adams, Institute of Environmental Studies, University of Wisconsin, based on the data obtained from the following sources.
  2. Lathrop, R. C. & Johnson, C. D. (1979) Water quality conditions. Dane County Water Quality, Appendix B. Dane County Regional Planning Commission, Madison, Wisconsin.
  3. Wessley, J., Nyenhuis, G. & Eaton, E. (1981) Lake Survey Map of Lake Mendota, Dane County. Wisconsin Department of Natural Resources, Madison, Wisconsin.
  4. National Climatic Centre (1982) Local Climatological Data, Annual Summary with Comparative Data, 1982, Madison, Wisconsin. National Oceanic and Atmospheric Administration, Environmental Data and Information Service, National Climatic Centre, Ashville, N. Carolina.
  5. Knapp, C. L. et. al. (1980) Insolation Data Manual. Solar Energy Research Institute.
  6. Dane County Regional Planning Commission (1979) Dane County Water Quality. Dane County Regional Planning Commission, Madison, Wisconsin.
  7. Fallon, R. D. & Brock, T. D. (1980) Planktonic blue-green algae: production, sedimentation and decomposition in Lake Mendota, Wisconsin. Limnol. & Oceanogr., 25: 72-88.
  8. Pedros-Alio, C. & Brock, T. D. (1982) Assessing biomass and production of bacteria in eutrophic Lake Mendota, Wisconsin. Appl. Environ. Microbiol., 44: 203-218.
  9. Brock, T. D. (1985) A Eutrophic Lake: Lake Mendota, Wisconsin. Ecological Studies 55. Springer-Verlag, New York, 308 pp.
  10. *Lillie, R. A. & Mason, J. W. (1983) Limnological Characteristics of Wisconsin Lakes. Technical Bulletin No. 183. Department of Natural Resources, Madison, Wisconsin. l0) *Pedros-Alio C., Woolsey, E. & Brock, T. D. (1985) Zooplankton dynamics in Lake Mendota: abundance and biomass of the metazooplankton from 1976 to 1980. Transactions of the Wisconsin Academy of Sciences.
  11. *Bardach, J. E. (1951) Changes in the yellow perch population of Lake Mendota, Wisconsin, between 1916 and 1948. Ecology, 32: 719-728.
  12. *Lathrop, R. C. (1979) Dane County Water Quality Plan. Appendix B: Water Quality Conditions; Appendix H: Lake Management. Dane County Regional Planning Commission, Madison, Wisconsin.
  13. *Sonzogni, W. C. & Lee, G. F. (1975) Phosphorus sources for the lower Madison lakes. Transactions of the Wisconsin Academy of Sciences, Arts, and Letters, 63: 162-175.

    14. * Cited from (8).