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LAKE DRUKSIAI

A view on the lakeshore

Photo: B.pernazaviciute and J.Datsenko

A. LOCATION

• Lithuania.
• 55:37N, 26:38E; 141.6 m above sea level.

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B. DESCRIPTION

Lake Druksiai is located in the northeastern part of Lithuanian Republic on the borderline between Lithuania and Belarus. Its northern part belongs to Belarus, where the lake is called Lake Drisvyaty. It belongs to the River Desna system spreading over the eastern slope of Baltic Hills and the lowland of Desna.

The landscape of the region is characterized by the relief formed by glacial action, consisting of picturesque mountain ridges, ravines, lakes and plains as well as by pine forests and vast water-meadows. In Desna basin, the crystalline bedrock lies at a depth of 750 m, and is overlaid by thick layers of sedimentary rocks belonging to Upper Proterozoic, Cambrian Ordovician, Silurian, Devonian and Quaternary horizons. The lithological composition of Quaternary sediments (90 m thick) deposited during the three glacial periods is diverse. Moraines of clay, clay loam, carbonate sapropel, sand, mixed sand and gravel, etc. have been detected.

Since 1984, the Ignalina Nuclear Power Plant (INPP) started operation using the lake as its cooling pond. The Scientific Base was established on the northern shore in 1978. The lake is now used for power generation, irrigation and fishery, and also for cultural and everyday needs (Q).

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C. PHYSICAL DIMENSIONS (Q)

Surface area [km2]	49.0
Volume [km3]	0.370
Maximum depth [m]	33.3
Mean depth [m]	7.6
Water level	Regulated
Normal range of annual water level fluctuation [m]	0.7
Length of shoreline [km]	60.5
Residence time [yr]	3
Catchment area [km2]	564

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D. PHYSIOGRAPHIC FEATURES (Q)

D1 GEOGRAPHICAL

• Bathymetric map: Fig. EUR-48-1.
• Number of main islands (name and area)
  Zamok (0.26 km²), Sosnovec (0.048 km²), Utovec (0.0088 km²) and 5 nameless islands.
• Number of outflowing rivers and channels (name): 1 (R. Prorva).

D2 CLIMATIC

• Climatic data at Dukstas, 1985-1989

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann.
Mean temp. [deg C]	-7.6	-7.4	-2.6	4.8	10.9	15.8	17.0	15.5	10.5	6.1	-3.1	-3.9	4.7
Precipitation [mm]	36.8	77.5	29.6	47.5	39.6	10.3	76.3	92.0	68.7	37.0	38.1	44.1	690

• Solar radiation: 12.8 MJ m^-2 day^-1.

Fig. EUR-48-1
Bathymetric map [m].

• Water temperature [deg C]

Station 1

1979

Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0.5	-	0.2	-	-	15.5	18.2	18.8	18.5	13.8	8.4	2.9	-
32	-	3.3	-	-	6.5	7.1	7.4	7.6	7.5	8.2	2.9	-
1989
0.5	-	4.8	8.5	11.2	16.2	22.1	24.5	22.0	16.6	11.1	-	-
32	-	4.1	7.0	7.9	9.1	9.4	9.7	9.8	9.9	10.5	-	-

Station 2

1979

Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0.5	-	0.2	-	-	13.6	19.2	17.3	18.9	14.0	8.6	3.2	-
33	-	3.3	-	-	6.6	7.6	7.8	8.5	8.5	8.4	3.1	-
1989
0.5	-	3.9	6.6	11.4	16.3	21.4	19.9	21.0	16.6	11.0	-	-
33	-	4.0	6.6	6.9	8.5	9.6	10.8	10.1	10.1	10.9	-	-

Station 4

1979

Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0.5	-	0.2	-	-	14.1	19.4	17.8	18.4	13.2	8.3	3.2	-
7	-	0.2	-	-	9.6	18.6	16.8	18.0	13.0	8.0	3.0	-
1989*
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0.5	-	14.2	17.4	21.0	26.0	29.5	28.3	27.2	26.2	19.0	-	-
7	-	5.6	17.4	10.4	17.1	25.0	19.3	20.2	16.6	12.2	-	-

* In the warm water discharge from INPP.

Station 5

1979

Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0.5	-	0.2	-	-	14.7	19.6	19.2	17.8	13.3	8.6	3.0	-
11	-	-	-	-	8.4	11.3	16.9	17.5	13.1	8.7	2.8	-
1989
0.5	-	-	10.0	10.4	18.5	24.2	20.1	22.8	17.9	-	-	-
11	-	-	9.1	9.7	14.4	17.1	18.5	18.9	17.0	-	-	-

Fig. EUR-48-2
Annual temperature profiles [deg C] at Station 2, respectively, before (1982) and after (1989) the start of INPP operation.

Fig. EUR-48-3
Vertical temperature distribution at Station 2.

• Freezing period
  From December to March (1977-1985) (since 1988 no ice coverage).
• Mixing type:
  Monomictic since 1988.
• Notes on water mixing and thermocline formation
  Summer thermocline in July August was at 12-17 m depth in 1977-1983, and at 14.5-17.5 m in 1986-1990.

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E. LAKE WATER QUALITY (2)

E1 TRANSPARENCY (1989)

Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
-	9.3	7.8	4.8	6.3	6.5	4.6	6.3	5.8	-	-	-

E2 pH (1979-1983)

Station	Depth [m]	Winter	Spring	Summer	Autumn
1 & 2*	0.5	7.1	7.3	7.3	7.3
	Bottom	7.3	8.1	7.5	8.0
3 & 5*	0.5	8.1	8.4	8.3	8.3
	Bottom	7.8	8.2	8.1	8.3
4 & 6*	0.5	8.2	8.3	8.3	8.3

* Combined sample.

E4 DO (1979-1983)

Station	Depth [m]	Winter		Spring		Summer		Autumn
		[mg l-1]	[%]*	[mg l-1]	[%]	[mg l-1]	[%]	[mg l-1]	[%]
1 & 2	0.5	14.2	100	12.7	112	10.2	108	12.0	104
	Bottom	5.1	39	12.1	98	2.7	23	8.1	66
3 & 5	0.5	13.9	98	12.6	117	10.1	107	12.0	104
	Bottom	10.6	75	12.6	109	8.9	89	11.3	101
4 & 6	0.5	13.6	96	12.7	116	10.0	105	12.1	104

* Percent saturation.

Fig. EUR-48-4
Vertical distribution of dissolved oxygen concentration (DO).
1: 17 July 1979. 3: 21 February 1979.
2: 31 July 1989. 4: 22 March 1989.

E5 COD [mg l^-1]

Determined by K2Cr2O7 method. (1979-1983)
Station	Depth [m]	Winter	Spring	Summer	Autumn
1 & 2	0.5	24.2	18.9	19.8	20.9
	Bottom	24.4	21.4	22.4	20.2
3 & 5	0.5	28.3	22.2	21.3	21.6
	Bottom	27.2	23.3	21.2	20.8
4 & 6	0.5	26.2	22.1	19.1	21.3

E6 CHLOROPHYLL CONCENTRATION [micro l^-1]

	1986			1987			1988
Depth [m]	May	Jul	Oct	May	Jul	Oct	May	Jul	Oct
0.5	0.29	2.12	1.51	0.89	1.99	0.92	2.40	5.35	1.58
Bottom	0.48	1.26	1.17	0.55	0.59	0.80	1.58	-	1.46

	1989			1990
Depth [m]	May	Jul	Oct	May	Jul	Oct
0.5	2.43	9.36	2.09	1.45	3.54	2.00
Bottom	-	-	-	1.08	-	-

E7 NITROGEN CONCENTRATION

• NO₃-N [mg l^-1] (1979-1983)

Station [m]	Depth	Winter	Spring	Summer	Autumn
1 & 2	0.5	0.05	0.03	0.03	0.06
	Bottom	0.14	0.12	0.15	0.10
3 & 5	0.5	0.06	0.01	0.01	0.06
	Bottom	0.10	0.06	0.03	0.10
4 & 6	0.5	0.08	0.02	0.02	0.07

NH₄-N [mg l^-1] (1979-1983)

Station [m]	Depth	Winter	Spring	Summer	Autumn
1 & 2	0.5	0.22	0.23	0.20	0.21
	Bottom	0.38	0.24	0.36	0.43
3 & 5	0.5	0.20	0.23	0.19	0.23
	Bottom	0.21	0.23	0.20	0.19
4 & 6	0.5	0.22	0.27	0.25	0.27

E8 PHOSPHORUS CONCENTRATION

• Total-P, 1984 1990
  0.052 [mg l^-1].

E10 PAST TRENDS

Average values for the whole lake [mg l-1]
Observation period	DO	COD	T-N	T-P
1979-1983	11.18	20.1	1.29	0.061
1984-1990	10.49	25.6	1.44	0.052

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F. BIOLOGICAL FEATURES (1)

Station 1, 3, 4, 6, 1984 1990

F1 FLORA

• Emerged macrophytes (dominant species)
  Phragmites australis, Schoenoplectus lacustris, Scolochloa festucacea.
• Floating macrophytes
  Nuphar lutea, Polygonum amphibium, Potamogeton natans.

F2 FAUNA

• Zooplankton
  Keratella cochlearis, Polyarthra euryptera, Bosmina longirostris, Daphnia cristata, D. cucullata, Leptodora kindtii, Mesocyclops leuckarti, M. oithonoides, Limnocalanus grimaldii var. macrurus.
• Benthos
  Littoral and sublittoral zones; Stictochironomus psammophilus, Psammoryctides barbatus, Lumbriculus variegatus, Potamothrix hammoniensis, Bithynia tentaculata, Dreissena polymorpha.
  Profundal zone; Chironomus anthracinus, Chaoborus flavicans, Pisidium amnicum, Procladius sp., Mysis oculata relicta, Pallasea quadrispinosa.
• Fish
  Abramis brama*, Esox lucius*, Rutilus rutilus*, Perca fluviatilis, Coregonus albula*, Osmerus eperlanus*, Alburnus alburnus, Carassius carassius, Gymnocephalus ceruna
  (* economically important).

F3 PRIMARY PRODUCTION RATE [mg C m^-2 day^-1]

Estimated by ¹⁴C method.

Station 1

Year	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
1985	-	-	-	-	7	52	32	112	-	22	-	-
1986	-	-	-	-	20	-	29	74	-	2	-	-
1987	-	-	-	-	1.4	-	26	223	-	30	-	-
1988	-	-	-	-	22	-	525	400	204	200	-	-
1989	-	-	-	-	42	105	292	855	300	140	-	-

F4 BIOMASS

• Biomass of phytoplankton [g m^-3 (wet wt.)] (1979-1983)

Station	Biomass of phytoplankton
1	0.41-1.47
2	0.30-1.26
3	0.67-1.84
4	0.64-1.66
5	0.57-1.80
6	0.30-1.26

• Biomass of zooplankton [mg m^-3 (wet wt.)]

Season	1981	1982	1988	1989	1990
Winter	-	-	38	50	25
Spring	230	460	539	299	708
Summer	1,390	1,790	2,140	1,481	1,158
Autumn	750	850	361	420	504

• Biomass of zoobenthos (1976-1984)

	[g m-2 (wet wt.)]	[metric tons]
Littoral zone	0.16-76.36	31.1
Sublittoral zone	1.63-6.30	51.3
Profundal zone	0.34-2.10	12.2

F5 FISHERY PRODUCTS

• Annual fish catch [metric tons]

Species	1950-1975	1976-1983	1984-1985	1986-1990
Bream	0.85	2.08	7.02	2.57
Pike	1.21	1.66	1.37	0.64
Roach	1.33	4.37	14.13	2.61
Perch	1.99	0.60	0.76	0.46
European cisco	1.81	2.39	0.88	0.03
Smelt	6.52	2.64	-	1.37
Ruff	1.62	0.01	5.35	-
Bleak	2.55	12.24	1.11	32.97
Crucian carp	0.01	0.01	-	0.15
Total	17.9	26.0	30.6	40.8

F7 NOTES ON THE REMARKABLE CHANGES OF BIOTA IN THE LAKE IN RECENT YEARS

After the completion of INPP, the diversity of phytoplankton species was decreased. The biomass of Bacillariophyta became more variable in different years and in different parts of the lake, probably owing to the rise of water temperature caused by the discharge of warm water from the nuclear power plant. The relative contribution of Pyrrophyta to the whole algal biomass increased, with associated changes in the dominant species. The number of zooplankton species became less than half of the previous number, the proportion of Crustacea increased, and the alternation of dominant species was observed. There was no significant change in zoobenthos biomass.

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G. SOCIO-ECONOMIC CONDITIONS

G1 LAND USE IN THE CATCHMENT AREA

	Area [km2]	[%]
Natural landscape
- Woody vegetation	57.5	10.2
- Swamps	69.9	12.4
Agricultural lands
- Crop field	220.0	39.0
- Meadows	216.6	38.4
Total	564	100

• Types of important forest vegetation
  Pine and spruce are dominant (80%). Birch, alder, aspen.
• Main kinds of crops: Barley, wheat, rye, oat.
• Levels of fertilizer application on crop fields: Moderate.

G2 INDUSTRIES IN THE CATCHMENT AREA AND THE LAKE (1990)

	Main products and major industries
Secondary industry	Butter making, bread bakery, Ignalina Nuclear Power Plant, concrete, iron-concrete construction plant, fuel apparatus repair plant

• Numbers of domestic animals in the catchment area
  Cattle 50,000, sheep 5,000, swine 80,000, poultry 100,000.

G3 POPULATION IN THE CATCHMENT AREA

	Population	Population density [km 2]	Major cities
Urban	32,300		Dukstas
Rural	13,000
Total	45,300	80

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H. LAKE UTILIZATION

H1 LAKE UTILIZATION

Sightseeing and tourism (1,000 visitors in 1990), recreation (swimming, sport- fishing and yachting), power generation, fisheries and aquaculture.

H2 THE LAKE AS WATER RESOURCE (1990)

	Use rate [m3 sec-1]
Power plant	80

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I. DETERIORATION OF LAKE ENVIRONMENTS AND HAZARDS

I1 ENHANCED SILTATION (2)

• Extent of damage: Not serious.
• Supplementary notes
  Sedimentation rate [kg m^-2 yr^-1]: 1.72 (Sta. 1), 2.88 2.91 (Sta. 2), 1.32 2.17 (Sta. 3).

I2 TOXIC CONTAMINATION (3)

• Main contaminants and their concentrations [mg l^-1]
  Station 4, 1981 1987

Name of contaminant	Range of concentrations
	Water	Bottom silt	Fish*3	Waterweed
137Cs	1.5×-13	2.2×-9	1.9×-10	5.0×-11
	6.0×-14	6.6×-9	5.2×-10	4.5×-10
134Cs	4.2×-14*1	6.3×-10*2	5.2×-12	6.5×-11
40K	1.4×-12	1.7×-8	4.3×-10	1.7×-8
	5.3×-13	8.0×-8	3.5×-9	9.0×-9
106Ru	-	7.3×-10*2	-	-
103Ru	1.4×-12	-	-	-
60Co	-	1.1×-11*2	-	-
232Th	1.4×-13	4.9×-10*2	-	-
226Ra	4.8×-13	6.3×-10*2	-	-
144Ce	1.2×-12	-	-	-

*1 9 September 1986. *2 8 July 1986. *3 Roach liver.

Concentration of some chemical elements in lake water [mg m^-3], Station 4, 1981-1987

	Range of concentrations
Mo	0.0-1.5
Cu	2.0-12.0
Zn	20-400
Co	0.5<-1.5
Br	0.11-14.1

• Supplementary notes
  The effects of INPP on the lake environment include thermal pollution and chemical pollution with radioactive and other substances. Sanitary and industrial wastewater are also sources of pollutants.

I4 ACIDIFICATION

• Extent of damage: Not serious.

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J. WASTEWATER TREATMENTS (Q)

J1 GENERATION OF POLLUTANTS IN THE CATCHMENT AREA

(e) Severe pollution with little or no wastewater treatment.

J2 APPROXIMATE PERCENTAGE DISTRIBUTION OF POLLUTANT LOADS

	[%]
Non-point sources (agricultural, natural and dispersed settlements)	15
Point sources
- Municipal	-
- Industrial	80
Others	5
Total	100

J3 SANITARY FACILITIES AND SEWERAGE

• Percentage of municipal population in the catchment area provided with
  adequate sanitary facilities or public sewerage: 90%.
• Percentage of rural population with adequate sanitary facilities: 10%.
• Number of industrial wastewater treatment systems: 1.

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K. IMPROVEMENT WORKS IN THE LAKE (Q)

Improvement works for INPP, such as the provision of power regulation system, automatic radioactive pollution control system, and new treatment facilities for radioactive wastes, are being planned by INPP and Environmental Protection Department of Lithuanian Academy of Science (LAS).

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L. DEVELOPMENT PLANS (Q)

None.

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M. LEGISLATIVE AND INSTITUTIONAL MEASURES FOR UPGRADING LAKE ENVIRONMENTS (Q)

M1 NATIONAL AND LOCAL LAWS CONCERNED

• Responsible authorities
  
  1. Environmental Protection Department
  2. INPP Administration

M3 RESEARCH INSTITUTES ENGAGED IN THE LAKE ENVIRONMENT STUDIES

1. Institute of Ecology, Lithuanian Academy of Science (LAS)
2. Institute of Physical and Technical Problems of Energetics, Kaunas
3. Institute of Geography and Institute of Botany, LAS
4. University of Vilnius

• Supplementary notes
  In 1989, a mass social movement ("Green Movement") was locally organized against the construction of Pulley-3 Plant of INPP.

N. SOURCES OF DATA

Questionnaire filled by Drs. B. Pernazaviciute, Institute of Ecology, Lithuanian Academy of Science and J. Datsenko, Dept. of Hydrology, Geography Faculty, Moscow State University.

1. Base State of the Populations and Communities of Water Animals in the Druksiai Lake (1986) Vilnius: Mokslas. 270 pp.
2. Radiation-Ecological Research of INPP in the Period before its Starting: Resulting Report (1985).
3. Trend and Intensity of Phytocenosis Succession in the Reservoir-Cooler and in the Region of INPP. Report of the Biological Institute of the Academy of Science of the Lithuanian SSR.

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