LAKE VORTSJARV

A view on the lakeshore

Photo.
Photo: J.Haberman


A. LOCATION

  • Viljandi, Tartu and Valga Counties, Estonia.

  • 58:05-58:26N, 25:24-26:09E; 33.7 m above sea level.


B. DESCRIPTION

    Lake Vortsjarv is the second largest lake of Estonia. The lake depression was formed in the pre-glacial period, but was later transformed by the action of inland ice which partly eroded the lake wall and partly filled the depression with deposits. The present lake has existed since the Middle Holocene. The basic substratum is formed by Middle Devonian deposits, which are exposed on steep banks on the eastern shore of the lake. Elsewhere the lake shore is rather low. The bottom of the depression around the lake is covered with moraine, fluvio-glacial sand and gravel, lacustrine/alluvial sand, clay and peat. About two-thirds of the lake bottom are covered with mud lying on marl. The total volume of the mud and marl amounts to 3.6x1.0E+9 million m3.
    The number of main tributaries is 18, the Vaike-Emajogi River being the most important. The outflowing River Suur-Emajogi drains into Lake Peipus, the fifth widest lake (3,555 km2) in Europe. The hydrologic feature of the lake is characterized by intensive and prolonged high water level in spring, low water level in summer and winter, and a noticeable rise of water level in autumn. On an average, one year is needed for a complete change of lake water. The whole lake is prevailingly homothermal in summer, while there is persistent inverse stratification in winter. The surface water temperature remains quite even all over the lake, local differences not exceeding 2deg C. Ice cover lasts for 135 days from November to April. Ice is the thickest in March.
    The lake is situated at some distance from industrial centres, and the drainage basin is mainly used for crop production and cattle breeding. About 36% of the catchment area is covered by forests.
    L. Vortsjarv has been strongly eutrophied, accumulating a great amount of biogenic substances. Oxygen deficit may sometimes take place under ice cover in the southern part of the lake and near the shore. Typical features of the lake water quality are its high buffer capacity and very large seston contents. The most important factors responsible for the present state of the lake are non-purified or only unsatisfactorily treated wastewater and excessive use of fertilizers in agriculture. Low water level brings about a rise in trophic level and is therefore dangerous. In order to keep the water level within an optimum range, it is planned to build a regulating lock at the head of the outflowing Suur-Emajogi River (1, 3).

C. PHYSICAL DIMENSIONS (1)

    Surface area [km2] 270.7
    Volume [km3] 0.760
    Maximum depth [m] 6
    Mean depth [m] 2.8
    Water level Unregulated
    Normal range of annual water level fluctuation [m] 1.4
    Length of shoreline [km] 96
    Residence time [yr] 1
    Catchment area [km2] 3,100

D. PHYSIOGRAPHIC FEATURES

D1 GEOGRAPHICAL (1)
  • Bathymetric map: Fig. EUR-47-1.

  • Number of main islands (name and area): Pahksaar, Tondisaar.

  • Number of outflowing rivers and channels (name): 1 (Suur-Emajogi R.).

D2 CLIMATIC
  • Climatic data at Toravere*, 1955 1989

    Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann.
    Mean temp. [deg C] -6.7 -6.5 -2.8 3.8 11.1 15.3 16.8 15.4 10.6 5.7 0.3 -3.9 4.9
    Precipitation [mm] 33 24 23 34 51 63 76 83 61 53 48 42 591
    * 23 km from the lake.

    Fig. EUR-47-1
    Bathymetric map [m].

  • Number of hours of bright sunshine: 1,625 hr yr-1 (7).

  • Solar radiation: 9.23 MJ m-2 day 1.

  • Water temperature [deg C]

    Rannu-Joesuu, 1947 1966 (1)
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0.3 - - 1.8 3.7 11.4 17.3 18.9 17.8 13.1 7.0 1.6 0.5
    Tondisaare (Station 1)*1, 1988 1991 (19)
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    S*2 0.3 0.9 2.1 4.1 12.1 18.0 20.5 17.9 13.4 6.4 1.5 0.1
    B*3 2.6 2.3 2.4 5.2 12.0 17.1 19.9 17.4 13.3 6.4 4.0 0.5
    *1 cf. Fig. EUR-47-4. *2 Surface. *3 Bottom.
  • Freezing period: From 11 November to 27 April.

  • Mixing type: Polymictic.

  • Notes on water mixing and thermocline formation
    In case of lasting sunshine (May June) a temporary weak thermocline (1 2deg C) may occur.

E. LAKE WATER QUALITY

E1 TRANSPARENCY [m](19)
    Tondisaare, 1989
    Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0.60 1.67 1.40 0.93 0.86 0.66 0.85 0.91 0.90 0.93 0.95 0.90
E2 pH (19)
    Tondisaare, 1989 1991
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0.3 7.11 7.88 8.07 8.10 8.64 8.39 8.48 8.53 8.50 8.35 8.10 -
E3 SS [mg l-1](9)
    Tondisaare, 1989 1991
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0.3 2 4 3 12 14 8 10 20 5 13 39 -
E4 DO [mg l-1](19)
    Tondisaare, 1989 1991
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0.3 12.3 12.2 12.5 12.2 12.2 9.3 11.6 12.3 10.6 11.9 14.3 14.4
    B* 5.2 9.0 7.2 12.1 12.0 10.7 10.9 10.5 10.4 11.9 12.5 11.6
    * Bottom.
E5 COD [mg l-1](19)
    Determined by KMnO4 method.
    Tondisaare, 1989 1991
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0.3 10 14 9 12 11 13 15 14 - 20 12 -
  • BOD [mg l-1](9)

    Tondisaare, 1989 1991
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0.3 2.7 2.4 2.8 4.0 4.9 4.5 4.3 5.2 3.4 3.5 2.3 -
E6 CHLOROPHYLL CONCENTRATION (12)
  • Chlorophyll a [micro l-1]

    Tondisaare, 1989 1991
    D*1 [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0.3 3.57 8.26 22.12 26.16 28.25 25.22 22.35 28.11 30.66 37.78 33.13 2.63
    B*2 2.22 8.37 16.71 27.85 30.40 34.08 25.19 30.43 33.84 38.89 32.29 2.00
    *1 Depth. *2 Bottom.

    Fig. EUR-47-2
    Average chlorophyll a and phaeopigments, 1989 1991.

E7 NITROGEN CONCENTRATION (9)
  • Total-N [mg l-1]
    Tondisaare, 1989 1991
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0.3 5.8 4.7 2.7 4.1 2.1 2.3 2.2 1.4 1.9 2.6 3.4 -
  • NH4-N [mg l-1]

    Tondisaare, 1989 1991
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0.3 0.55 0.20 0.24 0.07 0.08 0.21 0.06 0.19 0.09 0.13 0.07 -
  • NO2-N [mg l-1]

    Tondisaare, 1989 1991
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0.3 0.010 0.010 0.013 0.007 0.004 0.004 0.001 0.001 0.002 0.003 0.003 -
  • NO3-N [mg l-1]

    Tondisaare, 1989 1991
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0.3 3.50 1.10 1.04 1.08 0.46 0.24 0.02 0.04 0.04 0.19 0.29 -
  • Organic-N [mg l-1]

    Tondisaare, 1989 1991
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0.3 1.74 3.4. 1.45 2.79 1.61 1.82 2.09 1.17 1.80 2.16 3.02 -
E8 PHOSPHORUS CONCENTRATION
  • Total-P [mg l-1](9)

    Tondisaare, 1989 1991
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0.3 0.04 0.03 0.05 0.04 0.04 0.03 0.05 0.05 0.02 0.08 0.14 -
  • PO4-P [mg l-1](9)

    Tondisaare, 1989 1991
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0.3 0.04 0.01 0.02 0.01 0.01 0.01 0.02 0.02 0.01 0.03 0.05 -
  • Organic-P [mg l-1]

    Tondisaare, 1989 1991
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0.3 0.01 0.02 0.03 0.03 0.03 0.02 0.03 0.03 0.02 0.05 0.07 -
E9 CHLORIDE CONCENTRATION [mg l-1](9)
    Tondisaare, 1989 1991
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0.3 18 14 18 15 15 12 25 13 16 15 18 -
E10 PAST TRENDS
  • Trend of chlorine ion concentration

    April November
    1953 1989
    Range of fluctuation 0.10-0.12 0.34-0.43
    Mean +-SD 0.10+-0.01 0.37+-0.03

F. BIOLOGICAL FEATURES (1, 3) (1965-1967)

F1 FLORA
  • Emerged macrophytes
    Phragmites australis, Schoenoplectus lacustris, Nuphar luteum, Typha angustifolia.
  • Submerged macrophytes
    Potamogeton perfoliatus, P. lucens, Ceratophyllum demersum, Myriophyllum spicatum, M. verticillatum.
  • Phytoplankton
    Lyngbya limnetica (whole year dominant), L. contorta, Oscillatoria redekei (appeared in the 1960's), Melosira ambigua, M. islandica helvetica (spring), Stephanodiscus sp., Scenedesmus spinosus, Anabaena lemmermanni.
F2 FAUNA
  • Zooplankton
    Bosmina coregoni, Chydorus sphaericus, Daphnia cucullata, Mesocyclops crassus, M. leuckarti, M. oithonoides, Cyclops kolensis (winter), Anuraeopsis fissa, Filinia longiseta, F. terminalis (winter), Keratella cochlearis, K. quadrata frenzeli, K. hiemalis (winter), Polyarthra luminosa, P. dolichoptera (winter), Synchaeta verrucosa (winter).
  • Benthos: Chironomus plumosus, Potamothrix hammoniensis.

  • Fish
    Abramis brama*, Esox lucius*, Perca fluviatilis*, Anguilla anguilla*, Gymnocephalus cernua*, Rutilus rutilus*, Lota lota*, Idus idus*, Carassius carassius*, Tinca tinca*, Scardinius erythrophthalmus*, Alburnus alburnus*, Leuciscus leuciscus*, L. cephalus*, Hypomesus olidus*, Coregonus vandesius, Gobio gobio*, Misguranus anguillicaudatus, Pungitius sp., Cottus sp. (* economically important).
F3 PRIMARY PRODUCTION RATE [g C m-2](12)
    Determined by 14C method.
    Tondisaare, 1989
    Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total
    Photosynthesis 0.5 1.8 9.9 23.9 38.4 23.5 25.7 27.5 23.5 20.8 7.2 1.8 204.6
    Dark carbon fixation 0.9 1.4 2.3 3.2 15.4 12.6 9.9 13.5 6.8 2.3 1.4 0.9 70.4
    Total 1.4 3.2 12.2 27.1 53.7 36.1 35.7 41.1 30.3 23 8.6 2.7 275
F4 BIOMASS
  • Biomass of phytoplankton [g m-3 (wet wt.)](12)

    Average for 1979 1981
    Jan Feb Mar Apr May Jun
    Cyanophyceae 0.144 0.024 0.012 0.161 1.141 6.912
    Chrysophyceae 0.015 0.023 0.328 0.125 0.057 0.031
    Bacillariophyceae 0.004 0.063 2.988 2.363 5.270 2.568
    Euglenaceae 0.002 0.020 0.000 0.000 0.029 0.000
    Pyrrophyceae 0.000 0.016 0.209 0.000 0.132 0.630
    Chlorophyceae 0.021 0.010 0.009 0.210 0.070 0.143
    Jul Aug Sep Oct Nov Dec
    Cyanophyceae 9.740 5.717 5.711 10.076 3.242 0.371
    Chrysophyceae 0.017 0.021 0.010 0.011 0 0.001
    Bacillariophyceae 2.426 1.088 1.561 3.443 1.019 0
    Euglenaceae 0.000 0.037 0.000 0.000 0 0
    Pyrrophyceae 0.128 0.120 0.090 0.000 0 0.157
    Chlorophyceae 0.234 0.393 0.318 0.912 0.957 0.006
    Average for 1985-1991
    Year Winter Summer
    1985 0.98 15.96
    1986 0.91 29.24
    1987 0.66 7.14
    1988 4.96 20.78
    1989 7.00 15.80
    1990 5.54 9.06
    1991 2.62 14.38
  • Average biomass of zooplankton [g m-3]

    Jan Feb Mar Apr May Jun
    Cladocera 0.001 0.001 0.000 0.000 0.030 0.461
    Rotifera 0.028 0.010 0.009 0.023 0.032 0.072
    Copepoda 0.008 0.002 0.004 0.015 0.123 1.096
    Jul Aug Sep Oct Nov Dec
    Cladocera 0.546 0.834 0.114 0.379 0.089 0.005
    Rotifera 0.004 0.033 0.005 0.023 0.016 0.098
    Copepoda 0.749 0.740 0.055 0.041 0.003 0.000

    Fig. EUR-47-3
    Average zooplankton density, 1979 1981 (13).

  • Average population density [sp. m-2] and biomass [g m-2] of macrozoobenthos

    Population density Biomass
    1988 1989 1990 Average 1988 1989 1990 Average
    Chironomus plumosus 202 82 471 252 7.48 1.781 10.67 6.65
    Chironomidae 440 322 826 529 7.99 2.191 11.38 7.19
    Oligochaeta 523 174 383 360 0.75 0.281 0.85 0.63
    Mollusca 9 9 7 8 0.28 0.246 0.16 0.23
    Varria 23 18 21 21 0.21 0.073 0.07 0.12
    Total 995 523 1,237 918 9.23 2.791 12.46 8.16
  • Average biomass of fish (15) (1986-1989)

    Species [kg ha-1] [t]
    Abramis brama 45 1,215
    Anguilla anguilla 11 300
    Perca fluviatilis (>40 cm) 9.2 248
    Esox lucius (>40 cm) 4.3 116
    Total 114 3,075
F5 FISHERY PRODUCTS
  • Annual fish catch [metric tons](15) (1990)

    • 471.
F6 PAST TRENDS
  • Trend of plankton biomass (16)

    Phytoplankton [g m-3] Zooplankton [g m-3] Bacterioplankton [cells ml 1]
    Year Winter Summer Winter Summer Winter Summer
    1964 - 20.74 - 1.86 1.3 -
    1965 0.14 15.04 0.077 1.415 2.1 4.1
    1966 0.55 14.85 0.046 1.054 3.2 6
    1967 - - 0.034 1.286 1.4 6.5
    1968 0.47 13.35 0.011 1.228 3.7 7.7
    1969 0.15 11.7 0.016 0.252 4.0 7.3
    1970 0.52 34.67 0.005 1.634 2.5 7.4
    1971 0.62 57.59 0.009 1.512 3.7 7.6
    1972 5.01 30.76 0.027 1.376 8.7 9.1
    1973 7.4 36.59 0.058 1.022 6.17 10.7
    1974 5.91 29.89 0.007 0.562 3.5 7.8
    1975 0.79 47.78 0.008 1.236 3.5 4.1
    1976 0.12 19.55 0.041 0.881 5.1 5.3
    1977 0.9 27.76 0.008 1.965 5.9 9.2
    1978 0.29 22.22 0.02 0.56 2.6 3.8
    1979 0.15 10.4 0.024 1.612 3.2 3.8
    1980 0.14 8.8 0.033 1.666 2.1 3.5
    1981 3.63 7.9 0.006 1.08 3.9 5.3
    1982 0.96 10.67 0.005 1.166 3.7 4.0
    1983 1.27 15.66 0.021 0.558 3.8 5.1
    1984 1.27 14.75 0.031 1.424 2.9 3.9
    1985 0.98 15.96 0.022 0.958 2.5 4.0
    1986 0.91 29.24 0.009 0.939 3.2 3.8
    1987 0.66 7.14 0.028 1.901 2.4 2.3
    1988 4.96 20.78 0.029 1.118 2.6 2.8
    1989 7.00 15.80 0.041 0.908 3.3 3.3
    1990 5.54 9.06 0.075 0.489 2.0 2.9
    1991 2.62 14.38 0.044 0.995 3.6 -
  • Trend of fish catch

    Fish Ann. catch [metric tons]
    1952-1968 1969-1980 1981-1985 1986-1990
    Good quality fish 70.6 116.4 211.8 307.9
    - Eel (Anguilla) 0.4 24.4 38.1 64.8
    - Pike-perch (Perca) 4.7 43.0 48.8 46.1
    - Pike (Esox) 14.8 14.1 40.9 49.5
    - Bream (Abramis) >25cm 24.3 27.5 65.8 133.9
    - Perch (Gymnocephalus) >15 cm 11.2 3.9 7.7 6.9
    - Burbot (Idus) 5.2 3.5 10.5 6.7
    Less valuable small fish 238.9 70.2 108.1 230.1
    Total 309.5 186.6 319.9 538.0
    [%] of good fish 22.8 62.5 66.2 57.2

G. SOCIO-ECONOMIC CONDITIONS (17, 18)

G1 LAND USE IN THE CATCHMENT AREA (1989)
    Area [km2] [%]
    Natural landscape
    - Woody vegetation 1,100 36
    - Herbaceous vegetation 285 9
    - Swamp 310 10
    Agricultural land
    - Crop field 1,080 35
    - Pasture 290 9
    Residential area 35 1
    Total 3,100 100
  • Types of important forest vegetation
    Pine forest, spruce forest, birch forest, sandy heath, pine wood, swamp forest.
  • Types of important herbaceous vegetation
    Floodplain pasture, floodplain meadow.
  • Types of other important vegetation
    Fen, peat-bog, water-meadow, heath, raised bog, transitional bog.
  • Main kinds of crops
    Grain crops (barley, rye, wheat, oats), industrial crops (potato, flax, field grass).
  • Levels of fertilizer application on crop fields: Heavy.

  • Trends of change in land use in recent years
    During the last 20 years the following changes have occurred: 1) Polders came into use in the 1970's; 2) Accelerated building of summer cottages; 3) Decrease of natural grasslands; 4) Increase of cultivated grasslands; and 5) Slight decrease of forest area.
G2 INDUSTRIES IN THE CATCHMENT AREA AND THE LAKE (18) (1987)
    Gross product per year [103 rubles] (110 Rub.= 1 US$) No. of persons engaged No. of establishments Main products
    Primary industry
    - Crop production 110,867*1 9,420*1 39 Potato, flax, grain
    - Animal husbandry Milk, meat
    - Fisheries 1,761 (1986-1990) 30 1 Fresh fish, smoked eel
    Secondary industry 247,000*2 12,870*3 230 Food stuffs, timber, building material
    Tertiary industry 16,220
    *1 Excluding forest management.
    *2 Excluding construction industry.
    *3 Including construction industry.
  • Number of domestic animals in the catchment area
    Cattle 21,900, sheep 8,900, swine 162,000, poultry 350,000.
G3 POPULATION IN THE CATCHMENT AREA (18) (1989)
    Population Population density [km 2] Major cities (population)
    Urban 46,036 1,238.0 Viljandi (23,080)
    Rural 35,739 11.7
    Total 81,775 26.4 Valga-Valka (30,000)

H. LAKE UTILIZATION

H1 LAKE UTILIZATION
    Sightseeing and tourism (18,000 visitors), recreation (swimming, sport-fishing and yachting) and fisheries.
H2 THE LAKE AS WATER RESOURCES (Q) (1991)
    None.

I. DETERIORATION OF LAKE ENVIRONMENTS AND HAZARDS (Q)

I1 ENHANCED SILTATION
  • Extent of damage: Not serious.

I2 TOXIC CONTAMINATION
  • Present status: Detected but not serious.

  • Average contents of benzpyrene in water [10 10 g l-1](2, 11, 17)

    Sampling station No. of analyses 1976 No. of analyses 1977
    1 18 11.20+-4.71 20 1.84+-0.72
    2 18 7.40+-2.24 19 2.62+-1.34
    3 11 5.28+-0.98 4 0.28+-0.07
    4 4 11.91+-4.24 - -
    5 17 5.82+-1.90 20 1.28+-0.37
    6 4 1.75+-0.06 2 0.06
    7 2 0.26 - -
    8 - - 2 0.18
    9 - - 2 0.23
    10 - - 4 0.28+-0.09
    11 - - 4 0.26+-0.09
    12 - - 4 0.24+-0.02

    Fig. EUR-47-4: Location of sampling stations (2).

  • Seasonal fluctuations of benzpyrene contents in the lake water [10 10 g l-1]

    Year Sampling station Winter Spring Summer Autumn
    1976 1 25.46 0.05 2.60 6.47
    2 13.19 0.50 10.26 1.96
    3 5.53 0.00 11.37 3.99
    1977 1 2.77 0.11 0.30 0.99
    2 2.67 0.16 0.23 13.55
    3 0.92 0.28 0.40 3.80
  • Benzpyrene contents in bottom mud [micro kg 1 (dry wt.)] (1976-1977)

    No. of analyses Range Average
    9 0.14 53.8 11.88+-7.6
  • Benzpyrene contents in aquatic plants [micro kg 1 (dry wt.)]

    Species No. of analyses Range Average
    Nuphar luteum 4 1.05-5.52 2.52+-1.06
    Potamogeton perfoliatus 3 0.34-5.60 2.34+-1.34
    P. lucens 4 0.38-0.60 0.48+-0.05
    Ceratophyllum demersum 4 1.08-2.00 1.44+-0.02
    Myriophyllum spicatum 4 0.84-1.09 0.98+-0.06
    Schoenoplectus lacustris 4 0.32-1.03 0.58+-0.16
    Typha angustifolia 4 0.30-0.57 0.47+-0.06
    Phragmites australis 4 0.03-1.42 0.68+-0.29
  • Benzpyrene contents in fish muscles [micro kg 1 (wet wt.)] (1976-1977)

    Species No. of analyses Range Average
    Bream 15 0.13-10.00 3.20+-0.82
    Pike-perch 7 0.09-0.76 0.29+-0.087
    Perch 5 0.09-1.90 0.71+-0.32
    Pike 2 0.19-0.26 -
    Ruff 2 2.10-6.80 -
    Bleak 2 0.70-1.60 -
  • Contents of Hg
    August 1986
    Hg [ppm (dry wt.)]
    Water 0.04*
    Potamogeton perfoliatus 0.40
    Myriophyllum verticillatum 0.42
    Chironomidae larvae <0.01
    Anodonta cygnea (soft part) 0.02
    * [ppb].
  • Hg contents in fish muscles [ppm (wet wt.)]

    August 1986
    Species No. of analyses Hg
    Pike 13 0.15
    Perch 44 3.38
    Bream 33 3.3
    Roach 10 0.19
    Ruff 3 0.11
    Leak 6 0.20
  • Contents of heavy metals in bottom mud [ppm (dry wt.)]

    July 1986
    Hg Pb Cd Cu Zn Mn
    Central part 0.16 8.77 0.25 9.27 88 438
    Estuary of Rongu R. 0.06 0.1 6.0 11.4 116 223
    Estuary of Vaike-Emajogi R. 0.13 15.3 0.16 13.0 137 524
    Estuary of Ohne R. 0.09 1.6 0.18 4.3 40 313
    Estuary of Tarvastu R. 0.02 0.8 0.1 1.0 19 50
    Estuary of Tanassilma R. 0.16 8.3 0.5 9.9 109 223
  • Environmental quality standards for contaminants in the lake
    BOD5 <2.0 mg l-1; benzpyrene <0.005 micro l-1; Hg <0.5 mg m-3 [ppb].
  • Food safety standards for toxic contaminant residues
    Hg <0.5 mg m-3 [ppb] for drinking water; Hg <5.0 [ppb] for juice, milk, pear; Hg <0.5 [ppb] for fish (11).
I3 EUTROPHICATION (Q, 6, 8)
  • Nuisance caused by eutrophication
    Unusual algal bloom: Anabaena lemmermanni.
  • Nitrogen and phosphorus loadings to the lake [t yr-1](8) (1985)

    Sources Industrial Domestic Agricultural Natural Total
    T-N 700 370 1,855 785 3,710
    T-P 29 18 15 10 72

    Fig. EUR-47-5
    Balance between inflows and outflows (8).

I4 ACIDIFICATION (Q, 4)
  • Extent of damage: None.
    pH of rain water at Valga*, 1988
    Jun Jul Aug Sep
    6.5+-0.4 6.2+-0.1 6.3+-0.1 7.2
    * 32 km from the lake.
  • Supplementary notes
    As the buffer capacity of lake water is high, there is no apparent trend toward acidification.

J. WASTEWATER TREATMENTS (8, 17)

J1 GENERATION OF POLLUTANTS IN THE CATCHMENT AREA
    (d) Measurable pollution with limited wastewater treatment.
J2 APPROXIMATE PERCENTAGE DISTRIBUTION OF POLLUTANT LOADS (8)
    BOD5 T-N T-P
    Non-point sources 50 70 35
    Point sources
    Municipal 20 10 25
    Industrial 30 20 40
    Total 100 100 100

    Fig. EUR-47-6
    Distribution map of pollutant sources (8).

J3 SANITARY FACILITIES AND SEWERAGE (17)
  • Percentage of municipal population in the catchment area provided with
    adequate sanitary facilities: 85%.
  • Percentage of rural population with adequate sanitary facilities: 50%.

  • Municipal wastewater treatment system
    No. of primary treatment systems: 80 (oxidation ponds).
  • Number of industrial wastewater treatment systems
    4 (activated sludge plants).

L. DEVELOPMENT PLANS

    The project "Regulation of the water regime in Lake Vortsjarv". It is intended to construct a lock at the head of the outflowing river (Suur-Emajogi R.). The purpose of this project is;
    1. to regulate the water level in the lake by lowering the water level during the maximum run-off period (in spring) and raising the water level during the minimum run-off period (in summer and early winter),
    2. to improve ecological conditions for the biota of the lake, and
    3. to improve navigation and recreation conditions. Owing to financial difficulties the construction of lock has not been started yet.

M. LEGISLATIVE AND INSTITUTIONAL MEASURES FOR UPGRADING LAKE ENVIRONMENTS

M1 NATIONAL AND LOCAL LAWS CONCERNED (17)
  • Names of the laws (the year of legislation)

    1. The Act on the Use of Natural Environment and Natural Resources (1989)
    2. The Act on the Protection of Estonian Nature (1990)
    3. Instruction for the Determination of the Pollution Load (1990)
    4. The Act on the Development of Estonian Water Management (1990)
    5. The Regulation for the Taxation of the Use of Nature (1990)
    6. The Instruction for Taking Waste Water Samples, for Determining the Pollution Level and Price (1991)
  • Responsible authorities

    1. Limnological Station of the Institute of Zoology and Botany, Academy of Science, Estonia
    2. Ministry of Environment, Estonia
  • Main operations

    1. Water quality monitoring by Limnological Station of the Institute of Zoology and Botany (the monitoring program started in 1964)
    2. The determination of pollution load of L. Vortsjarv by Ministry of Environment of Estonia
M3 RESEARCH INSTITUTES ENGAGED IN THE LAKE ENVIRONMENT STUDIES
  1. Limnological Station of the Institute of Zoology and Botany, Academy of Science, Estonian Republic, Rannu

N. SOURCES OF DATA

  1. Questionnaire filled by Dr. Juta Haberman, Limnological Station of the Institute of Zoology and Botany, Estonian Republic.
  2. Timm, T. (ed.)(1973) Lake Vortsjarv. The Institute of Zoology and Botany, Tallin. 284 pp.*2
  3. The Institute of Experimental and Clinic Medicine (1979) Carcinogenic Substances in the Water Bodies of Estonia. Tallinn. 124 pp.*1
  4. Haberman, J. (ed.)(1984) The State of the Ecosystem of Lake Vortsjarv. The Institute of Zoology and Botany, Tartu. 123 pp.*2
  5. Frey, J., Frey, T., Rasta, E. & Pent\|O(s, )uk, J. (1988) On the pollution of the rainwaters and its possible effect on forests. Environment Protection 1, Information series, pp. 3 10. Tallinn.*2
  6. Hodrejarv, H. & Ott, R. (1988) Heavy Metals in the Environment of Estonia. Transactions of Tallinn Technical University, pp. 73 83. Tallinn.*1
  7. Haberman, J., Noges, P. & Pihu, E. (1988) Changes in the ecosystem of Lake Vortsjarv. Dynamics and Ecology of Wetlands and Lakes in Estonia (ed. Zobel, M.), pp. 188 204. Tallinn.
  8. Kivi, R. (ed.)(1990) Climate of Tartu and Its Changes during the Recent Decades. The Institute of Astrophysics and Atmospheric Physics, Tartu. 182 pp.*2
  9. Jarvet, A. & Laanemets, A. (1990) Lake Vortsjarv as a natural purification plant. Estonian Nature (a popular science journal of Estonian Academy of Science and Ministry of Environment), 11: 708 712.*2
  10. Data obtained from the Ministry of Environment of the Estonian Republic.
  11. Noges, P. Changes in ionic composition of Lake Vortsjarv (Estonian Republic). Limnologia (in press).
  12. Ott, R. Heavy metals in the ecosystem of Lake Vortsjarv (unpublished material).
  13. Data obtained from Noges, P., Limnological Station of the Institute of Zoology and Botany.
  14. Data obtained from Haberman, J., Limnological Station of the Institute of Zoology and Botany.
  15. Data obtained from Kangur, K., Limnological Station of the Institute of Zoology and Botany.
  16. Data obtained from Pihu, E., Jarvlt, A. & Kangur, A., Limnological Station of the Institute of Zoology and Botany.
  17. Data obtained from Haberman, J., Noges, P., Lokk, S. & Tammert, H., Limnological Station of the Institute of Zoology and Botany.
  18. Data obtained from Jarvet, A., The Ministry of Environment of Estonian Republic.
  19. Data obtained from the Department of Economic Geography of the Tartu University.
  20. Unpublished material of Limnological Station of the Institute of Zoology and Botany.

    21. *1 Printed in Russian.
    *2 Printed in Estonian.