LAKE BALATON

From the rooftop of Balaton Limnological Research Institue, Tihany

Photo.
Photo: A. Kurata




A. LOCATION





B. DESCRIPTION

    Lake Balaton was formed mainly by tectonic forces 12,000-20,000 years ago. Prior to the opening of Sio-canal in 1863, its water level was 3 m higher and its surface was about twice larger than at the present. With its surface area of 593 km2, Lake Balaton is the largest lake in Central Europe, but its mean depth is only 3.2 m.
    The main inflow, the Zala River, empties into the southwestern end of the lake, while the Sio-canal drains the water from the eastern basin into the River Danube.
    The lake is covered by ice in winter. In summer the average water temperature is 23deg C. The strong waves swirl up much sediments, rendering the transparency low.
    The major ions of the water are Ca2+, Mg2+ and HCO3-. The pH is 8.4, rising to higher values during intensive primary production. Oxygen deficiency is formed only temporarily in the western part of the lake in calm summer periods with algal blooms.
    The distribution of macrophytes is restricted by strong waves to a relatively narrow belt. Only 3 percent of the lake surface is covered by reeds, and even less by submerged macrophytes. The major primary producers are phytoplankton. Zooplankton is not abundant. Zoobenthos represents an important food for the fish. The annual commercial fish catch is 1200 tons.
    The southern shore of the lake consists of sandy beach, while on the northern shore there are mountains of volcanic origin with old ruins on their tops and vineyards on their slopes. The picturesque landscape and the water ideal for swimming and other water sports attract 2 million tourists annually.
    The sewage discharge from rapidly developing towns in the watershed, the growing use of fertilizers in agriculture and large animal farms increased the nutrient loading to the lake in the last decades. A rapid eutrophication became apparent by increased production and biomass of phytoplankton. Blooms of blue-green algae are frequent in the most polluted western part of the lake.
    A eutrophication control program has been formulated, based on intensive scientific researches. Most of the municipal sewage is now diverted from recreational areas. Phosphorus removal was introduced at other sewage treatment plants. A reservoir was constructed to retain the nutrients carried by the Zala River. Pollution due to liquid manure was reduced. Construction of more reservoirs on major tributaries of the lake and a soil protection program are in progress (Q).


C. PHYSICAL DIMENSIONS

    Surface area [km2] 593
    Volume [km3] 1.9
    Maximum depth [m] 12.2
    Mean depth [m] 3.3
    Water level Regulated
    Normal range of annual water level fluctuation [m] 0.3
    Length of shoreline [km] 236
    Residence time [yr] 2
    Catchment area [km2] 5,181


D. PHYSIOGRAPHIC FEATURES (2)

D1 GEOGRAPHICAL

D2 CLIMATIC

    Mean temp. [deg C]*1
    Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann.
    -1.4 0.6 5.0 10.7 15.6 19.4 20.8 20.2 16.3 10.8 5.6 1.0 10.4
    Precipitation [mm]*2
    36.5 37.7 35.6 44.7 60.4 80.8 73.3 62.4 48.4 42.9 65.5 45.7 633.9
    *1 1947-1963. *2 1951-1980.

    Fig. EUR-04-01
    Bathymetric map (Q).



    1947-1963
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    1 - - 4.5 11.5 17.6 21.9 23.2 22.9 19.2 13.3 6.9 2.0


E. LAKE WATER QUALITY (3)

E1 TRANSPARENCY [m]

    Keszthely, 1979-1983
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    - - 0.49 0.38 0.50 0.47 0.50 0.35 0.41 0.46 0.50 0.65
    Szemes, 1979-1983
    - - 0.72 0.48 0.49 0.56 0.69 0.45 0.64 0.53 0.60 0.52
    Siofok, 1979-1983
    - - 0.71 0.45 0.45 0.71 0.67 0.55 0.69 0.70 0.57 1.25

E2 pH

    8.4, rising to 8.9 in the western part of the lake during summer algal blooms.

E3 SS [mg l-1]

    Keszthely, 1979-1983
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    1 - - 34.1 39.6 27.6 40.6 23.1 31.7 23.4 25.8 - 14.5
    Szemes, 1979-1983
    1 - - 20.7 22.2 22.5 13.9 16.4 29.1 13.5 22.6 56.0 13.4
    Siofok, 1979-1983
    1 - - 16.1 19.7 23.9 13.7 25.0 23.1 13.6 18.6 20.1 4.9

E4 DO [mg l-1]

    The dissolved O2 concentration is usually close to the saturation level. Strong oversaturation at the surface and O2 deficiency near bottom sediment are found only in the western part of the lake in calm summer periods during algal blooms.

E5 COD [mg l-1]

    Keszthely, 1979-1983
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    1 - - 7.86 8.60 6.50 7.38 9.80 7.72 7.96 8.00 8.07 9.80
    Szemes, 1979-1983
    1 - - 5.96 5.10 5.00 4.68 6.32 5.64 6.04 6.45 5.95 5.00
    Siofok, 1979-1983
    1 - - 4.88 4.80 4.02 3.26 4.70 4.46 4.46 4.67 4.43 4.90

E6 CHLOROPHYLL CONCENTRATION [micro g l-1]

    Keszthely, 1979-1983
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    1 - - 34.0 30.8 19.8 20.4 33.5 51.4 38.4 41.4 42.8 42.9
    Szemes, 1979-1983
    1 - - 12.4 19.4 10.6 7.4 8.8 22.6 19.5 16.7 15.4 16.1
    Siofok, 1979-1983
    1 - - 7.2 9.2 8.5 4.4 5.4 9.8 11.7 10.0 6.8 5.1

E7 NITROGEN CONCENTRATION

    Keszthely, 1979-1983
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    1 - - 1.81 1.85 1.23 1.50 1.39 2.01 1.51 1.57 1.72 1.94
    Szemes, 1979-1983
    1 - - 1.25 0.98 0.90 0.92 0.87 0.99 0.87 1.19 1.09 0.63
    Siofok, 1979-1983
    1 - - 0.93 0.80 0.72 0.61 0.70 0.79 0.71 1.07 0.69 0.59

E8 PHOSPHORUS CONCENTRATION

    Keszthely, 1979-1983
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    1 - - .075 .089 .068 .089 .101 .104 .114 .089 .143 .078
    Szemes, 1979-1983
    1 - - .032 .052 .036 .033 .035 .037 .039 .040 .059 .043
    Siofok, 1979-1983
    1 - - .024 .028 .034 .022 .027 .028 .033 .043 .031 .028


F. BIOLOGICAL FEATURES

F1 FLORA (4)

F2 FAUNA (5)

F3 PRIMARY PRODUCTION RATE [mg C m-2 day-1](6, 7)

    Keszthely, 1973
    Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann.
    312 447 524 594 726 858 6,640 6,628 2,265 126 434 373 613*
    Szemes, 1976
    127 96 447 432 496 988 1,551 1,132 841 386 214 159 210*
    Siofok, 1977
    103 105 248 616 633 951 1,228 847 638 313 203 41 181*
    * [g C m-2 yr-1].

F4 BIOMASS

F5 FISHERY PRODUCTS

F6 PAST TRENDS: Fig. EUR-04-02, 03, 04, 05 and 06.

    Fig. EUR-04-02
    Trend of increase of primary production in the Keszthely-basin (6).


    Fig. EUR-04-03
    Trend of increase of algae counts in the Keszthely-basin (4).


    Fig. EUR-04-04
    Trend of increase of algae counts in the Siofok-basin (4).


    Fig. EUR-04-05
    Trend of increase of phytoplankton biomass in the Keszthely-basin (4).


    Fig. EUR-04-06
    Trend of increase of phytoplankton biomass in the Siofok-basin (4).



G. SOCIO-ECONOMIC CONDITIONS (8)

G1 LAND USE IN THE CATCHMENT AREA

    1982
    Area [km2] [%]
    - Natural landscape
    Woody vegetation 1,343 25.9
    Herbaceous vegetation 362 7.0
    Swamp 106 2.0
    - Agricultural land
    Crop field 2,428 46.9
    Pasture land 505 9.7
    - Residential area 437 8.4
    - Others - -
    - Total 5,181 100.0

G2 INDUSTRIES IN THE CATCHMENT AREA AND THE LAKE

    1980
    No. of persons engaged No. of establishments
    Primary industry 46,400
    Animal husbandry 334
    Secondary industry 65,200 741
    Tertiary industry 78,900

G3 POPULATION IN THE CATCHMENT AREA

    Population Population density [km-2] Major cities (population)
    Urban 180,500 Zalaegerszeg, Tapolca,
    Rural 224,300 Marcali, Keszthely,
    Total 404,800 64 Siofok, Balatonfured


H. LAKE UTILIZATION

H1 LAKE UTILIZATION

    Source of water, navigation and transportation, sightseeing and tourism (no.of visitors in 1982: 1,800,000), recreation (swimming, sport-fishing,yachting) and fisheries.

H2 THE LAKE AS WATER RESOURCE

    Use rate [m3 sec-1]
    Domestic 0.273
    Irrigation 0.079
    Industrial 0.330
    Power plant -
    Others -


I. DETERIORATION OF LAKE ENVIRONMENTS AND HAZARDS

I1 ENHANCED SILTATION

I2 TOXIC CONTAMINATION (9)

    Name of contaminant Range of concentration [ppm] in*1 Main sources
    Water Bottom mud Fish*2 Other organisms
    1982 1984 1982 1982*3 1982*4 1982*5
    Cu (0.005) (10) (3.12) (12.3) (18.6) (42.5) Waste
    Zn (0.057) (90) (64.3) (468) (73.5) (111) dumps and
    Ca (0.0008) (1.5) (0.65) (3.7) (3.99) (1.47) agriculture
    Hg (0.0007) (-) (0.36) (1.22) (1.88) (1.08)
    Pb (0.002) (30) (3.59) (48.5) (22.1) (12.3)
    *1 For water on volume basis mg l-1; for bottom mud, fish and other organisms on dry weight basis mg kg-1.
    *2 Abramis brama, muscle.
    *3 Anodonta oygnea, pill.
    *4 Chironomidae larvae, whole animals.
    *5 Crustacean plankton.

I3 EUTROPHICATION

    1975-1981
    Sources Industrial Domestic Agricultural Natural Total
    T-N - 382 1,973 - 3,148
    T-P - 89 150 - 314


J. WASTEWATER TREATMENTS (Q)

J1 GENERATION OF POLLUTANTS IN THE CATCHMENT AREA

    f) Extensive development of the catchment area with provision for municipal wastewater treatment.

J3 SANITARY FACILITIES AND SEWERAGE


M. LEGISLATIVE AND INSTITUTIONAL MEASURES FOR UPGRADING LAKE ENVIRONMENTS

M1 NATIONAL AND LOCAL LAWS CONCERNED

M2 INSTITUTIONAL MEASURES

  1. National Water Authority

M3 RESEARCH INSTITUTES ENGAGED IN THE LAKE ENVIRONMENT STUDIES

  1. Balaton Limnological Research Institute of the Hungarian Academy of Sciences, Tihany
  2. Research Centre for Water Resources Development
  3. National Public Health Institute
  4. Karl Marx University of Economics
  5. Scientific and Design Institute for Urban Planning
  6. Institute for Environmental Protection


N. SOURCES OF DATA

  1. Questionnaire filled by Dr. S. Herodek, Balaton Limnological Research Institute of the Hungarian Academy of Sciences, Tihany.
  2. Illes I. (ed.)(1981) Our Lake Balaton. Natura Press, Budapest (in Hungarian).
  3. National Meteorological Service-Data Bank.
  4. Research Centre for Water Resources Development-Data Bank.
  5. Voros, L. (1985) Phytoplankton changes in space and time in Lake Balaton. D. Sc. Thesis (in Hungarian).
  6. Ponyi, J. E. (1986) Pelagic and benthic invertebrates of Lake Balaton and their ecology. D. Sc. Thesis (in Hungarian).
  7. Herodek, S. & Tamas, G. (1976) The primary production of phytoplankton in the Keszthely-basin of Lake Balaton in 1973-1974. Annal. Biol. Tihany, 42: 175-190.
  8. Herodek, S., Voros, L. & Toth, F. (1982) The mass and production of phytoplankton and the eutrophication in Lake Balaton III. The Balatonszemes basin in 1976-1977 and the Siofok basin in 1977. Hidrol. Kozl., 62: 220-229 (in Hungarian with English summary).
  9. National Authority for Environment Protection and Nature Conservation (1984) Balaton 1982.
  10. Salanki, J. V., Balogh, K. & Berta, E. (1982) Heavy metals in animals of Lake Balaton. Water Research, 16: 1147-1152.