LUNZER SEE

A view of the whole lake

Photo.
Photo: H. Loffler


A. LOCATION

  • Nieder-Osterreich, Austria.
  • 47:51N, 15:04E; 608 m above sea level.

B. DESCRIPTION

    Lunzer Untersee (Lower Lunz Lake) is of glacial origin, and located approximately 120 km southwest of Vienna. There are two small neighboring lakes, Mittelsee (Middle Lake) and Obersee (Upper Lake) in the upstream of the Seebach, the main inflowing river to Untersee. The lake is only 0.7 km2 wide, has a maximum depth of 33.7 m, and a fairly short residence time (0.7 year). The nutritional level of the lake water is still oligotrophic, but the littoral zone has recently been eutrophicated considerably, with remarkable changes in the aquatic flora.
    Ninety percent or more of the total drainage basin area consist of karstic plateau and the forests of Norway spruce and European beech. The density of year-round population in the drainage basin is low (11 km-2), but summer visitors may amount to 8,000 day-1 at the maximum. Domestic waste water of this district has been diverted to preserve the quality of the lake water.

C. PHYSICAL DIMENSIONS (Q)

    Surface area [km2] 1
    Volume [km3] 0.013
    Maximum depth [m] 33.7
    Mean depth [m] 20.0
    Water level Unregulated
    Length of shoreline [km] 4.2
    Residence time [yr] 0.3
    Catchment area [km2] 27

D. PHYSIOGRAPHIC FEATURES

D1 GEOGRAPHICAL (Q)
  • Bathymetric map: Fig. EUR-10-01.
  • Names of main islands: None.
  • Number of outflowing rivers and channels (name): 1 (Seebach-Ausrinn R.).
D2 CLIMATIC (Q)
  • Climatic data at Lunz Biological Station*
    Mean temp. [deg C]
    Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann.
    -4.5 -2.1 1.9 6.6 11.1 14.3 16.1 15.4 12.7 7.5 2.2 -1.6 6.6
    Precipitation [mm]
    108 121 109 132 148 200 243 193 116 117 107 114 1,706
    * 20-year mean.
  • Number of hours of bright sunshine (1927-1948): 1,312 hr yr-1.
  • Snowfall
    Period of snowfall (1927-1948): 1 November-15 April. Depth of maximum snow accumulation (1981): 1.25 m.

    Fig. EUR-10-01
    Bathymetric map (Q).

  • Water temperature [deg C](Q)
    Station 1, 1981
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    1 2.4 2.5 4.5 7.6 10.7 12.9 11.9 13.9 12.4 9.8 5.8 2.6
    5 3.6 3.2 4.0 7.6 9.4 11.3 11.5 13.7 12.1 9.8 5.8 2.7
    10 3.6 3.4 3.9 6.3 7.6 9.4 9.8 11.0 10.8 9.8 5.8 2.8
    15 3.6 3.4 3.7 5.2 5.6 6.7 9.0 9.0 8.8 9.8 5.8 3.0
    20 3.6 3.4 3.7 4.6 5.0 5.4 5.8 5.5 5.8 5.8 5.8 3.0
    30 3.9 3.4 3.7 4.2 4.5 4.6 5.0 4.9 4.9 5.0 5.7 3.5
  • Freezing period: March-December.
  • Notes on water mixing and thermocline formation
    The thermocline is formed from middle May to early October. Strong effect of flushing by the tributary Seebach.

E. LAKE WATER QUALITY

E1 TRANSPARENCY: Fig. EUR-10-02.

    Fig. EUR-10-02
    Seasonal trend of transparency [m], Station 1, 1981 (2).

E2 pH (1)
    Station 1, 1981
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    S* 7.7 7.5 7.7 7.6 7.6 7.9 7.7 7.4 7.4 7.4 7.2 7.7
    * Surface.
E4 DO [mg l-1]
    Station 1, 1981
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    1 10.8 12.4 13.9 15.1 14.7 12.3 11.4 11.5 12.0 12.2 11.7 11.7
    5 10.8 12.4 14.7 14.9 14.8 11.8 11.9 11.7 12.4 12.6 10.3 11.5
    10 10.9 12.2 13.8 15.5 15.7 12.3 11.7 12.1 11.8 12.6 9.9 11.8
    15 10.9 12.2 12.8 13.9 13.9 12.0 11.9 11.5 11.4 12.2 10.1 11.4
    20 10.9 11.9 12.7 12.6 12.0 10.2 9.5 8.9 9.1 9.3 9.9 11.4
    30 10.9 11.1 10.8 11.2 9.8 6.7 6.0 5.1 3.5 2.9 9.5 11.2
E6 CHLOROPHYLL CONCENTRATION [mg m-2](Q)
    1975
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0-20* 0.77 1.65 0.73 3.1 5.8 1.6 1.3 1.2 2.6 2.4 1.2 1.4
    * Integrated sample.
E8 PHOSPHORUS CONCENTRATION
  • Total-P [micro g l-1]
    Station 1, 1981
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    1 5.3 14.0 5.0 7.0 5.3 6.0 5.7 8.0 7.3 5.7 5.7 6.7
    5 5.7 8.3 7.0 9.0 5.3 8.7 7.7 8.0 10.3 8.0 5.0 6.7
    10 5.7 8.7 6.3 7.3 6.0 5.0 6.7 5.7 4.0 6.3 5.7 8.0
    15 5.7 8.3 5.7 5.0 6.0 3.7 7.0 6.7 3.7 5.0 6.7 6.7
    20 6.3 9.3 7.0 5.3 5.7 4.0 4.0 2.7 3.7 4.7 5.7 6.7
    30 6.7 16.3 10.7 8.7 8.0 4.0 4.7 4.3 10.7 14.0 6.0 6.3

F. BIOLOGICAL FEATURES

F1 FLORA
  • Emerged macrophytes: Phragmites australis, Scirpus lacustris (Q).
  • Submerged macrophytes (Q)
    Elodea canadensis, Potamogeton praelongus, P. Perfoliatus, P. pusillus, P. pectinatus.
  • Phytoplankton (3)
    Mallomonas akrokomos, Dinobryon divergens, Cyclotella operculata, Stephanodiscus alpinus, Rhodomonas minuta, Cryptomonas ovata.
F2 FAUNA
  • Zooplankton (3)
    Rotifera (Keratella cochlearis, Polyarthra vulgaris, P. major); Cladocera (Daphnia longispina hyalina); Copepoda (Eudiaptomus gracilis).
  • Fish: Salvelinus alpinus, Phoxinus phoxinus, Gobio gobio, Cottus gobio (Q).
F3 PRIMARY PRODUCTION RATE (Q)
  • Net primary production rate [mg C m-2 day-1]
    1976
    Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann.
    184.4 - 140.9 440 320 462 119 231 270 186 137 90 233
F4 BIOMASS: Fig. EUR-10-03, 04 and 05.

    Fig. EUR-10-03
    Phytoplankton biomass [mg l-1], 1981 (2).

    Fig. EUR-10-04
    Percent contribution of various algal groups to the total algal volume, 1981 (2).

    Fig. EUR-10-05
    Zooplankton biomass (cell volume, the centre of the lake)(3).

F5 FISHERY PRODUCTS (Q)
  • Annual fish catch
    Not estimated (sport-fishing only).
F7 NOTES ON THE REMARKABLE CHANGES OF BIOTA IN THE LAKE IN RECENT YEARS (Q)
  • No change in the plankton, but change in the littoral zone toward eutrophication; less species in diatoms and Cyanophyceae and more green algae.

G. SOCIO-ECONOMIC CONDITIONS

G1 LAND USE IN THE CATCHMENT AREA (Q)
    1978
    Area[km2] [%]
    - Natural landscape
    Woody vegetation 17.4 64.6
    Rocky barrens 7.6 28.3
    - Agricultural land
    Meadows 1.8 6.5
    - Residential area 0.2 0.6
    - Total 27.0 100.0
  • Main types of woody vegetation
    Picea abies, Fagus silvatica, Acer montana, Larix decidua.
G3 POPULATION IN THE CATCHMENT AREA
    1970
    Population Population density [km-2] Major cities (population)
    Total 300 11 In summer up to 8,000 tourists per day

H. LAKE UTILIZATION

H1 LAKE UTILIZATION
  • Tourism and recreation (swimming, sport-fishing).

I. DETERIORATION OF LAKE ENVIRONMENTS AND HAZARDS

I1 ENHANCED SILTATION (Q)
  • Extent of damage: None.
I3 EUTROPHICATION (Q)
  • Nitrogen and phosphorus loadings to the lake [t yr-1]
    1981 T-P: 0.394.

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 treatment system (activated sludge) for domestic wastewater present. The treated effluent is diverted to the outside of the lake's drainage basin.

N. SOURCES OF DATA

  1. Questionnaire filled by Dr. G. Malicky, Lunz Biological Station, Lunz.
  2. Pambalk, I. & Schlott, G. (1982) Osterr. Eutrophieprogramm: Fortsetzung der Untersuchungen des OECD-Projektes (Temperatur, Sauerstoff, Phosphor, pH, Leitfahigkeit). Jber. Biol. Stat. Lunz, 5: 111-115.
  3. Malicky, G. (1982) Das Phytoplankton des Lunzer Untersee im Jahr 1981. Jber. Biol. Stat. Lunz, 5: 125-127.
  4. Ruttner-Kolisko, A. (1978) Durchflutung und Produktion im Lunzer Untersee. Jber. Biol. Stat. Lunz, 1: 98-115.