ZURICHSEE

A lakeside view

Photo.
Photo: Shiga Prefecutual Government




A. LOCATION

  • Zurich and Schwyz, Switzerland.
  • 47:15N, 8:40E; 406 m above sea level.


B. DESCRIPTION

    The Lake Zurich consists of two parts, a longer one with a length of about 28 km and a smaller one with a length of about 12 km. The lake lies in a valley formed by a glacier in the last ice period. With the state capital, the city of Zurich at the end of the lake, hilly shore areas offer favorable sites to live. Owing to the sewage discharge from this area, the lake became eutrophic at the beginning of this century. With the construction of sewage treatment plants, which include mechanical, biological and chemical steps in the form of phosphorus flocculation and flocculation filtration for all the wastewater in the catchment area, the loading of organic material and phosphorus compounds has been reduced, and the trophic state has tended toward mesotrophic. For one hundred years Lake Zurich water has been used as an important drinking water resource for Zurich and for various villages in its surroundings. The lake has a great importance also as a large recreation area.


C. PHYSICAL DIMENSIONS (Q1).

    Surface area [km2] 65
    Volume [km3] 3.3
    Maximum depth [m] 136.0
    Mean depth [m] 51.0
    Water level Regulated
    Residence time [yr] 1.1
    Catchment area [km2] 1,740


D. PHYSIOGRAPHIC FEATURES

D1 GEOGRAPHICAL (Q1)

  • Bathymetric map: Fig. EUR-06-01.
  • Names of main islands: None.
  • Number of outflowing rivers and channels (name): 1 (Limmat R.).

D2 CLIMATIC

  • Climatic data at Zurich, 1931-1960 (1)

    Mean temp. [deg C]
    Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann.
    -0.1 0.3 4.5 8.6 12.7 15.9 17.6 17.0 14.0 8.6 3.7 0.1 8.5
    Precipitation [mm]
    Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann.
    74 70 66 80 107 136 143 131 108 80 76 65 1,136
  • Number of hours of bright sunshine: 1,963 hr yr-1 (1).

    Fig. EUR-06-01
    Bathymetric map (Q1).


  • Water temperature: Fig. EUR-06-02.

    Fig. EUR-06-02
    Depth/season isotherms [deg C] at Station 1, 1983 (1).


    Fig. EUR-06-03
    Seasonal variation of vertical water temperature [deg C] distribution, 1972-1974 (2).


  • Freezing period: Seldom (1).
  • Mixing type: Meromictic (1).


E. LAKE WATER QUALITY

E1 TRANSPARENCY [m](Q1)

    Station 1, 1983
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    5.9 8.0 8.0 4.4 3.4 5.9 4.3 2.4 3.3 4.6 5.5 5.5

E2 pH (Q1)

    Station 1, 1983
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    S* 8.02 7.75 8.02 8.12 8.60 8.69 8.61 8.57 8.19 8.72 8.72 7.91
    * Surface.

E4 DO: Fig. EUR-06-04.

    Fig. EUR-06-04
    Vertical and seasonal distribution of DO [mg l-1](Q1).


E5 COD [mg l-1](Q3)

    Station 1, 1986
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 1.30 - - 1.35 - - 1.45 - - 1.45 - -
    1 - - - - - - - - - 1.50 - -
    2.5 - - - - - - - - - 1.50 - -
    5 - - - 1.20 - - 1.45 - - 1.50 - -
    7.5 - - - - - - - - - 1.45 - -
    10 1.20 - - 1.15 - - 1.45 - - 1.35 - -
    12.5 - - - - - - - - - 1.30 - -
    15 1.25 - - 1.15 - - 1.30 - - 1.25 - -
    20 1.20 - - - - - 1.25 - - 1.20 - -
    30 1.25 - - 1.10 - - 1.20 - - 1.20 - -
    40 1.30 - - 1.40 - - 1.20 - - 1.15 - -
    60 1.30 - - 1.35 - - 1.20 - - 1.15 - -
    80 1.15 - - 1.30 - - 1.20 - - 1.20 - -
    90 1.15 - - 1.35 - - - - - 1.10 - -
    100 1.10 - - 1.30 - - 1.20 - - 1.15 - -
    110 1.20 - - 1.30 - - - - - 1.15 - -
    120 1.25 - - 1.25 - - 1.15 - - 1.20 - -
    130 1.25 - - 1.30 - - 1.15 - - 1.30 - -
    135 1.40 - - 1.30 - - 1.25 - - 1.35 - -

E6 CHLOROPHYLL CONCENTRATION [micro g l-1](Q1)

    Station 1, 1983
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 0.54 1.04 1.70 3.74 11.54 1.78 1.82 3.83 2.17 3.68 1.30 0.40
    10 0.39 1.12 1.61 2.22 5.72 1.62 2.59 2.89 2.02 1.89 1.26 0.42
    20 0.32 1.12 0.58 0.58 1.16 0.31 0.35 0.38 0.42 0.62 0.36 0.36
    30 0.36 1.06 0.35 0.40 0.71 0.22 0.12 0.16 0.27 0.16 0.13 0.38
    40 0.28 1.04 0.47 0.35 0.56 0.15 0.11 0.11 0.29 0.14 0.10 0.07
    80 0.04 0.32 0.53 0.29 0.22 0.11 0.08 0.10 0.17 0.06 0.05 0.04
    120 0.02 0.13 0.15 0.19 0.16 0.10 0.04 0.06 0.10 0.25 0.05 0.05
    135 0.02 0.07 0.08 0.21 1.52 0.11 0.06 0.08 0.16 0.25 0.02 0.03

E7 NITROGEN CONCENTRATION (Q3)

  • NH4-N [mg l-1]

    Station 1, 1986
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 .025 .005 <.005 .005 .010 .070 .025 .010 .020 .010 .010 .015
    1 .025 .005 <.005 .005 .015 .070 .025 .010 .015 .010 .015 .015
    2.5 .025 .005 <.005 .005 .015 .070 .025 .010 .015 .010 .010 .015
    5 .025 .005 <.005 .005 .020 .075 .025 .015 .015 .010 .010 .015
    7.5 .025 .005 <.005 .010 .045 .075 .040 .030 .015 .015 .010 .015
    10 .025 .005 <.005 .010 .035 .005 .020 .035 .010 .010 .010 .015
    12.5 .025 .005 <.005 .010 .035 .005 .005 .005 .005 .005 .010 .015
    15 .025 .005 <.005 .010 .035 .005 .005 .005 .005 .005 .010 .015
    20 .030 .005 .005 .005 .005 .005 <.005 .005 .005 <.005 <.005 .005
    30 .030 .005 .005 .005 .005 .005 <.005 .005 .005 <.005 <.005 .005
    40 .030 .005 .005 .005 .005 .005 <.005 .005 .005 <.005 <.005 .005
    60 .005 .010 .005 .005 .005 .005 <.005 .005 .005 <.005 <.005 .005
    80 .005 .005 .005 .005 .005 .005 <.005 <.005 .005 <.005 <.005 .005
    90 .005 .005 <.005 .005 .005 .005 <.005 <.005 <.005 <.005 <.005 .005
    100 .005 .005 <.005 .005 .005 .005 <.005 .005 .005 <.005 <.005 .005
    110 .005 .005 <.005 <.005 .005 .005 .005 .005 .005 <.005 <.005 .005
    120 .005 .005 <.005 <.005 .005 .005 .005 .005 .005 <.005 .005 .005
    130 .040 .005 <.005 .005 .005 .005 .005 .005 .005 .200 .180 .200
    135 .300 .010 .005 .010 .005 .005 .005 .090 .135 .300 .320 .370
  • NO3-N [mg l-1]

    Station 1, 1986
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 .690 .735 .760 .770 .615 .655 .530 .375 .385 .370 .515 .555
    1 .705 .745 .750 .770 .625 .660 .530 .385 .365 .365 .520 .555
    2.5 .685 .740 .750 .775 .615 .650 .530 .375 .365 .365 .515 .555
    5 .690 .735 .750 .775 .615 .665 .540 .420 .370 .370 .520 .555
    7.5 .680 .710 .755 .775 .695 .690 .660 .490 .380 .380 .515 .550
    10 .695 .735 .760 .785 .740 .780 .775 .760 .765 .640 .515 .555
    12.5 .695 .730 .765 .795 .755 .775 .860 .865 .865 .845 .515 .550
    15 .705 .715 .760 .790 .760 .775 .865 .860 .870 .855 .515 .545
    20 .695 .730 .755 .780 .775 .770 .860 .905 .875 .845 .780 .800
    30 .700 .735 .760 .785 .775 .770 .850 .860 .855 .840 .800 .830
    40 .715 .760 .750 .785 .780 .770 .835 .845 .855 .825 .810 .840
    60 .855 .745 .775 .790 .785 .770 .835 .845 .845 .820 .805 .830
    80 .845 .755 .775 .790 .775 .770 .845 .840 .850 .820 .800 .825
    90 .840 .745 .800 .785 .780 .765 .845 .850 .855 .825 .805 .830
    100 .850 .785 .810 .790 .785 .770 .855 .845 .855 .825 .815 .830
    110 .845 .780 .815 .800 .785 .775 .860 .850 .865 .855 .815 .835
    120 .865 .780 .815 .800 .785 .785 .845 .865 .880 .650 .815 .855
    130 .805 .790 .815 .805 .785 .795 .870 .925 .830 .580 .670 .635
    135 .575 .780 .800 .790 .785 .805 .895 .755 .595 .480 .535 .500

E8 PHOSPHORUS CONCENTRATION

  • PO4-P [micro g l-1]

    Station 1, 1986 (03)
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 27 42 35 48 2 10 4 5 2 1 <1 1
    1 26 44 37 48 2 11 3 3 2 1 <1 1
    2.5 27 45 37 50 2 9 8 2 2 <1 <1 1
    5 27 45 37 50 1 11 2 3 2 <1 <1 1
    7.5 28 45 39 47 2 17 7 2 2 <1 <1 1
    10 28 46 43 48 13 12 5 2 2 <1 <1 1
    12.5 29 46 44 47 23 27 2 3 3 <1 <1 1
    15 27 46 45 46 28 37 12 2 2 <1 <1 <1
    20 26 48 45 49 37 47 34 8 9 17 17 25
    30 27 49 45 53 42 49 51 47 44 33 30 37
    40 28 49 44 54 43 49 52 53 52 47 47 47
    60 63 48 49 54 44 48 50 54 55 54 52 56
    80 69 61 60 54 45 53 56 57 60 59 55 63
    90 73 63 71 56 52 59 58 63 66 66 60 68
    100 81 90 77 57 51 66 65 65 79 73 67 72
    110 92 92 87 71 58 70 72 79 91 86 74 88
    120 126 118 101 79 45 73 89 96 115 130 114 125
    130 180 136 119 89 58 91 123 160 209 237 193 211
    135 259 142 133 96 60 126 160 223 301 267 252 268

    Fig. EUR-06-05
    Vertical and seasonal distribution of PO4-P [micro g l-1] at Station 1, 1983 (Q1).


  • Total-P [micro g l-1](Q3)

    Station 1, 1986
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 31 46 41 53 10 18 5 4 4 <1 3 1
    1 31 49 43 50 12 15 4 2 4 <1 4 2
    2.5 32 49 45 54 12 15 10 1 6 1 4 1
    5 37 49 44 52 10 19 9 5 8 1 7 1
    7.5 31 50 46 48 8 18 14 2 5 <1 4 1
    10 31 50 54 49 22 17 10 5 7 <1 4 1
    12.5 32 50 50 49 30 32 7 6 7 <1 4 1
    15 32 50 51 49 37 43 20 4 5 <1 4 <1
    20 32 51 50 52 45 50 42 9 15 17 24 25
    30 32 52 52 53 52 59 60 48 47 34 40 37
    40 32 53 51 56 50 54 60 53 53 49 51 47
    60 66 52 55 55 51 54 55 54 56 56 54 57
    80 71 64 65 55 55 58 64 55 61 61 58 67
    90 74 65 76 58 60 61 64 62 68 68 64 70
    100 83 92 82 58 58 71 73 65 79 76 71 74
    110 94 90 90 74 64 75 77 78 92 91 82 89
    120 130 119 101 79 66 80 94 95 118 140 117 142
    130 191 136 121 89 76 103 130 160 209 254 197 218
    135 263 142 135 96 78 128 165 223 305 291 260 282

E9 CHLORIDE CONCENTRATION [mg l-1](Q3)

    Station 1, 1986
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 4.2 4.2 4.0 4.4 4.2 3.5 3.4 2.7 3.1 3.0 3.7 4.0
    1 4.2 4.2 4.0 4.4 4.2 3.5 3.4 2.7 3.0 3.0 3.7 3.0
    2.5 4.2 4.2 4.0 4.4 4.2 3.5 3.4 2.6 3.0 3.0 3.7 3.0
    5 4.2 4.2 4.1 4.4 4.2 3.6 3.4 2.8 3.0 3.0 3.7 3.0
    7.5 4.2 4.2 4.1 4.4 4.5 4.2 3.4 2.4 3.0 3.1 3.7 3.0
    10 4.2 4.2 4.2 4.4 4.5 4.4 3.5 3.5 3.5 3.5 3.7 3.0
    12.5 4.2 4.2 4.2 4.4 4.6 4.4 4.1 4.1 4.0 4.0 3.7 3.0
    15 4.2 4.2 4.2 4.4 4.6 4.4 4.3 4.2 4.2 4.3 3.7 3.0
    20 4.2 4.2 4.3 4.4 4.5 4.4 4.4 5.4 4.4 4.4 4.3 4.0
    30 4.2 4.3 4.3 4.4 4.5 4.4 4.5 4.4 4.5 4.4 4.4 4.0
    40 4.4 4.3 4.3 4.4 4.5 4.4 4.5 4.4 4.5 4.4 4.5 4.0
    60 4.4 4.3 4.3 4.4 4.5 4.4 4.5 4.4 4.5 4.4 4.5 4.0
    80 4.4 4.3 4.4 4.4 4.5 4.4 4.5 4.4 4.5 4.5 4.5 4.0
    90 4.4 4.2 4.4 4.4 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.0
    100 4.4 4.3 4.4 4.4 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.0
    110 4.4 4.3 4.3 4.4 4.5 4.5 4.6 4.4 4.6 4.5 4.5 4.0
    120 4.4 4.5 4.2 4.4 4.5 4.5 4.5 4.4 4.6 4.5 4.5 4.0
    130 4.4 4.4 4.2 4.4 4.5 4.5 4.5 4.4 4.5 4.5 4.6 4.0
    135 4.4 4.4 4.1 4.4 4.5 4.5 4.5 4.4 4.5 4.5 4.5 4.0

E10 PAST TRENDS: Fig. EUR-06-06, 07, 08, 09 and 10.

    Fig. EUR-06-06
    Trend of transparency (means for January-March, 1897-1900 & 1936-1980)(3).


    Fig. EUR-06-07
    Trends of net hypolimnetic oxygen consumption during the stagnation period, and annual hypolimnetic oxygen minimum. Net hypolimnetic oxygen consumption is equivalent to annual maximum (spring) minus annual minimum (autumn)(3).


    Fig. EUR-06-08
    Trends of NO3-N and PO4-P in summer stagnation periods (2).


    Fig. EUR-06-09
    Past trend of annual averages of PO4-P (0-136 m)(Q3).


    Fig. EUR-06-10
    Past trends of total phosphorus in the eplilimnion and O2 in the hypolimnion between April and September (Q3).



F. BIOLOGICAL FEATURES (Q1)

F1 FLORA

  • Emerged macrophytes
    Phragmites communis, Phalaris arundinacea, Schoenoplectus lacustris.
  • Floating macrophytes
    Nymphaea alba, Nuphar luteum (several places but mostly planted by inhabitants).
  • Submerged macrophytes
    Potamogeton pectinatus, P. perfoliatus, P. lucens, P. crispus, Elodea canadensis, Zannichellia palustris.
  • Phytoplankton
    Anabaena flos-aquae, A. planctonica, Oscillatoria rubescens, Aphanizomenon flos-aquae, Pandorina morum, Sphaerocystis schroeteri, Mougeotia sp., Dinobryon divergens, Ceratium hirundinella, Cryptomonas ovata, Rhodomonas sp., Melosira granulata, Cyclotella comta, Stephanodiscus hantzschii, Tabellaria fenestrata, Fragilaria crotonensis, Asterionella formosa, Synedra acus.

F2 FAUNA

  • Zooplankton
    Nassula aurea, Tintinnopsis lacustris, Epistylis rotans, Polyarthra platyptera, Keratella cochlearis, Keratella quadrata, Notholca longispina, Asplanchna priodonta, Synchaeta pectinata, Leptodora sp., Daphnia longispina, Bosmina longirostris, Diaptomous gracilis, Cyclops strenuus, Chaoborus crystallinus.
  • Benthos
    Dugesia polychroa, Herpobdella octoculata, Helobdella stagnalis, Limnodrilus hoffmeisteri, Tubifex ignotus, Psammocryctes barbatus, Stylaria lacustris, Planaria sp., Bithynia tentaculata, Gyraulus albus, Lymnaea auricularia, L. peregra, Pisidium subruncatum, P. moitessierianum, P. nitidum, Dreissena polymorpha, Eucyclops serratulus, Paracyclops fimbriatus, Canthocamptus staphilinus, Caenis moesta, Polypedilum nubeculosum, Microtendipes sp., Limnochironomus pulsus, Eukjefferiella sp., Polycentropus flavomaculatus, Tinodes sp.
  • Fish
    Anguilla vulgaris, Esox lucius, Salmo salvelinus, S. variabilis, Coregonus wartmanni, C. schinzi, Leucisus rutilus, Abramis brama, Barbus fluviatilis, Tinca vulgaris, Cyprinus carpio, Lota vulgaris, Perca fluviatilis.

F3 PRIMARY PRODUCTION RATE

  • Net primary production rate [mg C m-2 day-1]

    Station 1, 1981
    Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann.
    67 8 710 2,050 370 1,180 1,470 910 1,130 940 603 560 833
    Station 1, 1982
    390 420 210 760 460 1,450 2,430 1,070 1,070 380 610 140 783

F5 FISHERY PRODUCTS

  • Annual fish catch [metric tons]: 189.4.

F6 PAST TRENDS (Q1)

  • Trends of net primary production rate and phytoplankton biomass

    0-14 m
    1974 1975 1976 1977 1978 1979 1980 1981 1982
    Primary production rate 350 230 390 230 250 280 180 305 290
    [g C m-2 yr-1]
    Phytoplankton biomass - - 2.56 2.23 2.05 3.34 2.48 1.35 2.87
    [mg l-1]


G. SOCIO-ECONOMIC CONDITIONS

G1 LAND USE IN THE CATCHMENT AREA (Q2)

    1980
    Area [km2] [%]
    - Natural landscape
    Woody vegetation 40.2 23
    Others 243.6 14
    - Agricultural land 922.3 53
    - Residential area 88.0 5
    - Others 104.4 6
    - Total 1,758.5 100
  • Main types of woody vegetation (Q1)
    Picea abies, Abies alba, Fagus silvatica, Quercus robur, Pinus silvestris, Larix decidua.
  • Main types of herbaceous vegetation (Q1)
    Fertilized meadow land (Agrostis, Bromus, Poa, Festuca, Lolium, Avena).
  • Levels of fertilizer application on crop fields: Moderate.

G2 INDUSTRIES IN THE CATCHMENT AREA AND THE LAKE (Q1)

  • Main products of agriculture: Wheat, grape, vegetables and dairy products.
  • Main kinds of manufacturing products: Textile, machinery and metal.

G3 POPULATION IN THE CATCHMENT AREA (Q1)

    1984
    Population Population density [km-2] Major cities (population)
    Total ca. 500,000 ca. 217 Zurich* (423,000), Stafa, Thalwil, Horgen, Wadenswil, Kusnacht, Meilen.
    * Not all the city area is included in the catchment area.


H. LAKE UTILIZATION

H1 LAKE UTILIZATION (Q1, Q2)

  • Source of water, fisheries, navigation, tourism and recreation (swimming, sport-fishing, yachting).

H2 THE LAKE AS WATER RESOURCE (Q1)

    1983
    Use rate [m3 sec-1]
    Domestic* 2.2
    Industrial 0.07
    * The lake serves as a source of drinking water for 700,000 people comprising the city of Zurich, its suburbs and lakeshore communities.


I. DETERIORATION OF LAKE ENVIRONMENTS AND HAZARDS

I1 ENHANCED SILTATION (Q3)

  • Extent of damage: Not serious.

I2 TOXIC CONTAMINATION (Q3)

  • Present status: Detected but not serious.
  • Main contaminants, their concentrations and sources
    Station 1, 1986

    Name of contaminants Concentrations [ppb] Water Main sources
    1, 1, 1-Trichloroethane 0.01 Industrial
    Trichloroethylene 0.01 Industrial
    Tetrachloroethylene 0.02 Industrial
    Afrazin 0.06 Different pollution sources

I3 EUTROPHICATION (Q3)

  • Nuisance caused by eutrophication
    Unusual algal bloom (Aphanizomenon flos-aquae and Stephanodiscus hantzschii).
  • Nitrogen and phosphorus loadings to the lake [ton yr-1]

    1984
    Sources Rivers Treated sewage Stormwater tank Untreated sewage Precipitate Total
    T-P 78 38 4 3 5 128

I4 ACIDIFICATION (Q3)

  • Extent of damage: None.


J. WASTEWATER TREATMENTS (Q1, Q3)

J1 GENERATION OF POLLUTANTS IN THE CATCHMENT AREA

    f) Extensive coverage of pollution sources by treatment systems.

J3 SANITARY FACILITIES AND SEWERAGE

  • Percentage of municipal population in the catchment area provided with
    adequate sanitary facilities (on-site treatment systems) or public sewerage: 90%.
  • Municipal wastewater treatment systems (rate of treatment: 130,000 m3 day-1)
    No. of quarternary treatment systems: 2. No. of tertiary treatment systems: 15 (activated sludge, with chemical precipitation of phosphorus).
  • Supplementary notes
    About 90% of sewage is treated in existing wastewater treatment systems. All of the 17 treatment plants will have a flocculation filtration process at the end.


M. LEGISLATIVE AND INSTITUTIONAL MEASURES FOR UPGRADING LAKE ENVIRONMENTS

M1 NATIONAL AND LOCAL LAWS CONCERNED (Q1, Q2)

  • Names of the laws (the year of legislation)
    1. Law of Water Rights, Canton of Zurich (1901)(similar for Canton of Schwyz)
    2. Federal Law on Water Pollution Control, Federal Government (1971)
    3. Law on the Introduction of the Federal Law of Water Pollution Control, Canton of Zurich (1974)(similar for Canton of Schwyz)
    4. Ordinance on Waste Water Disposal, Federal Government (1975)
    5. Law on Fisheries, Canton of Zurich (1976)
  • Responsible authorities
    Governments of Cts. of Zurich and Schwyz (Directorates of Hydraulic Constructions, Water Pollution Control, Fisheries, and Sanitation).
  • Main items of control
    Supervision of planning, maintenance and efficiency of water and waste treatment plants, and analysis of public waters (Cantonal Laboratories Zurich and Schwyz; City Water Supply Zurich).

M2 INSTITUTIONAL MEASURES

  1. Water Supply Zurich, Quality Control

M3 RESEARCH INSTITUTES ENGAGED IN THE LAKE ENVIRONMENT STUDIES

  1. Eidgenossische Anstalt fur Wasserversorgung, Abwasserreinigung und Gewasserschutz (EAWAG, part of the Swiss Federal Institute of Technology), Dubendorf
  2. Limnological Station at Kilchberg, University of Zurich


N. SOURCES OF DATA

  1. Questionnaire filled by Prof. K. Wuhrman, Institut fur Gewasserschutz und Wassertechnologie, Dubendorf.
  2. Questionnaire filled by Dr. P. Liechti, Bundesamt fur Umweltschutz, Zurich.
  3. Questionnaire filled by Dr. U. Zimmermann, Wasserversorgung Zurich, Zurich.
  4. Muller, M. J. (1982) Selected Climatic Data for a Global Set of Standard Stations for Vegetation Science. 306 pp. Dr. W. Junk Publishers, The Hague.
  5. Zimmermann, U. (1975) Gas-Wasser-Abwasser, 55(9): 473-480.
  6. Schanz, F. & Thomas, E. A. (1981) Reversal of eutrophication in Lake Zurich. Water Quality Bulletin, 6(4): 108-112 & 156.