LAKE PAIJANNE

A view of the sub-basin of Tehinselika


Photo: A. Makela

A. LOCATION

• Keski-Soumi, Hame, and Mikkeli, Finland.
• 61:14-62:15N, 25:10-26:00E; 78 m above sea level.

B. DESCRIPTION

Lake Paijanne is the second largest lake in Finland and the major lake of the River Kymijoki watercourse in central Finland. The basin of the lake lies in the old Precambrian primary rock consisting mainly of granite and schist. Loose ground consists mostly of till. The lake was formed after the last glacial period some 8,000 years ago, when the land began to rise with the retreat of ice and the connection with the sea was severed.
Lake Paijanne is 120 km long and its width varies from 1 to 28 km. There are several separate basins along the lake. Nutrient loadings mainly enter the northern part of the lake. The water quality is therefore poorer in the northern than in the southern part.
The total area of the drainage basin of Lake Paijanne is 25 times as large as the lake itself. Most of the basin is covered by forests, the proportion of farmland being only about 10%, and forested peatlands account for 25%. From the peatlands, humic substances are discharged to the lake. The forests consist mainly of pine and spruce. The population in the drainage basin is about 400,000, of which 150,000 live near the lake. There are some 30,000 holiday cottages along the shore of the lake.
Lake Paijanne is an important water resource which supplies drinking water to about 1 million people in the Helsinki metropolitan area. Water is conducted from the lake through a 120 km tunnel. The water quality in northern parts of the lake deteriorated definitely in the 1950's and 1960's. As the result of recent legislative and administrative measures, waste loadings have now diminished substantially and water quality has been steadily improved (Q).

C. PHYSICAL DIMENSIONS (Q)

Surface area [km2]	1,100
Volume [km3]	17.8
Maximum depth [m]	98
Mean depth [m]	17
Water level	Regulated
Normal range of annual water level fluctuation [m]	1
Length of shoreline [km]	1,140*
Residence time [yr]	2.7
Catchment area [km2]	25,400
* With islands 2,250 km.

D. PHYSIOGRAPHIC FEATURES (Q)

D1 GEOGRAPHICAL

• Bathymetric map: Fig. EUR-19-01.
• Names of main islands: Judinsalo (20 km2) and Virmalansaari (30 km2).
• Number of outflowing rivers and channels (name): 1 (Kalkkistenkoski).

D2 CLIMATIC

• Climatic data at Luonetjarvi, 1931-1960

Mean temp. [deg C]
Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann.
-9.4	-9.2	-5.4	-1.4	8.1	13.3	16.3	14.1	8.8	3.0	-1.6	-5.8	2.6
Precipitation [mm]
37	28	25	32	41	56	71	74	63	58	47	40	576

• Solar radiation: 8.8 MJ m-2 day-1.

Fig. EUR-19-01
Bathymetric map.

• Water temperature [deg C]

Station 70, 1985
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
1	0.4	-	0.1	-	3.7	17.7	-	18.7	-	8.0	-	-
10	1.2	-	0.6	-	3.7	9.1	-	15.8	-	8.0	-	-
20	2.6	-	1.7	-	3.7	6.2	-	7.4	-	8.0	-	-
30	2.2	-	2.1	-	3.7	5.6	-	6.0	-	8.0	-	-
40	2.5	-	2.3	-	3.7	5.4	-	5.6	-	-	-	-
60	2.8	-	2.6	-	3.7	5.1	-	5.3	-	-	-	-
Station 78, 1985
1	0.5	-	0.5	-	5.3	11.2	-	15.8	-	-	5.8	-
10	0.9	-	1.0	-	5.1	11.5	-	14.4	-	-	5.8	-
20	1.0	-	1.2	-	5.0	11.4	-	9.2	-	-	5.8	-
30	1.1	-	1.5	-	4.9	11.8	-	8.5	-	-	5.8	-
B*	1.3	-	1.6	-	4.8	11.9	-	8.3	-	-	5.8	-
* Bottom-1.

• Freezing period: December-May.
• Mixing type: Dimictic.

E. LAKE WATER QUALITY (Q)

E1 TRANSPARENCY [m]

Station 70, 1985
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
	2.6	-	3.6	-	3.7	2.4	3.0	2.4	2.8	2.9	-	-
Station 78, 1985
	2.5	-	2.5	-	4.5	5.4	4.7	3.3	4.9	-	3.8	-

E2 pH

Station 70, 1985
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
1	6.4	-	6.3	-	6.5	7.2	-	6.8	-	6.8	-	-
10	6.6	-	6.4	-	6.5	6.6	-	6.6	-	6.7	-	-
20	6.6	-	6.5	-	6.5	6.5	-	6.2	-	6.8	-	-
40	6.6	-	6.6	-	6.5	6.5	-	6.1	-	-	-	-
60	6.6	-	6.6	-	6.5	6.5	-	6.1	-	-	-	-
Station 78, 1985
1	6.9	-	7.0	-	6.8	7.0	-	6.8	-	-	7.0	-
10	6.9	-	6.9	-	6.9	7.0	-	6.7	-	-	7.0	-
20	6.8	-	6.9	-	6.9	6.9	-	6.4	-	-	7.0	-
30	6.8	-	6.9	-	6.9	6.9	-	6.4	-	-	7.0	-
B*	6.8	-	6.8	-	6.9	6.9	-	6.4	-	-	7.0	-
* Bottom-1.

E4 DO [mg l-1]

Station 70, 1985
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
1	11.0	-	10.3	-	10.9	10.9	-	9.5	-	10.1	-	-
10	11.7	-	12.2	-	10.5	10.5	-	8.2	-	10.0	-	-
20	11.6	-	12.2	-	10.3	10.5	-	8.9	-	10.0	-	-
30	11.8	-	11.9	-	10.5	10.5	-	9.3	-	10.0	-	-
40	11.3	-	11.8	-	10.2	10.4	-	9.5	-	-	-	-
60	11.4	-	11.5	-	10.7	10.5	-	9.3	-	-	-	-
Station 78, 1985
1	13.4	-	13.8	-	12.6	11.2	-	9.4	-	-	11.3	-
10	13.3	-	13.3	-	12.6	11.5	-	9.1	-	-	11.3	-
20	13.1	-	12.9	-	12.4	11.4	-	9.1	-	-	11.1	-
30	12.9	-	12.5	-	12.5	11.8	-	9.4	-	-	11.2	-
B*	12.6	-	12.0	-	12.5	11.9	-	9.4	-	-	11.4	-
* Bottom-1.

E5 COD [mg l-1]

Determined by KMnO4 method.

Station 70, 1985
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
1	11	-	11	-	9.3	11	-	9.1	-	8.5	-	-
10	10	-	10	-	9.5	9.8	-	9.0	-	8.6	-	-
20	9.7	-	9.0	-	9.3	10	-	8.8	-	8.6	-	-
30	9.5	-	8.1	-	9.3	9.7	-	8.8	-	8.4	-	-
40	9.7	-	9.0	-	9.5	9.8	-	8.8	-	-	-	-
60	9.8	-	8.7	-	10	9.9	-	8.9	-	-	-	-
Station 78, 1985
1	7.4	-	8.0	-	6.7	7.5	-	7.1	-	-	7.1	-
10	6.9	-	7.8	-	7.1	7.7	-	7.0	-	-	7.1	-
20	6.9	-	7.5	-	7.3	7.7	-	7.0	-	-	7.1	-
30	6.9	-	7.3	-	7.3	7.4	-	6.9	-	-	7.3	-
*1	6.9	-	7.2	-	7.4	7.4	-	6.9	-	-	7.3	-
*2	-	-	-	-	-	7.6	-	-	-	-	-	-
*1 Bottom-1. *2 Bottom.

E6 CHLOROPHYLL CONCENTRATION [micro g l-1]

Station 70, 1985
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0-2	-	-	-	-	0.6	12.3	4.2	13	9.6	-	-	-
Station 78, 1985
0-2	-	-	-	-	3.6	2.7	4.1	3.5	2.4	-	-	-

E7 NITROGEN CONCENTRATION

• Total-N [mg l-1]

Station 70, 1985
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
1	0.61	-	0.84	-	0.67	0.59	-	0.50	-	0.59	-	-
10	0.62	-	0.58	-	0.67	0.60	-	0.50	-	0.59	-	-
20	0.58	-	-	-	0.67	0.60	-	-	-	0.59	-	-
40	0.56	-	0.53	-	0.67	0.62	-	0.61	-	-	-	-
60	0.58	-	-	-	0.64	0.59	-	-	-	-	-	-
Station 78, 1985
1	0.57	-	0.56	-	0.52	0.51	-	0.44	-	-	0.52	-
10	0.48	-	0.50	-	0.56	0.51	-	0.44	-	-	0.53	-
20	0.50	-	0.52	-	0.54	0.53	-	0.51	-	-	0.54	-
30	0.50	-	0.52	-	0.57	0.54	-	-	-	-	0.54	-
B*	0.60	-	0.51	-	0.56	0.54	-	0.53	-	-	0.53	-
* Bottom-1.

E8 PHOSPHORUS CONCENTRATION

• Total-P [mg l-1]

Station 70, 1985
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
1	0.016	-	0.016	-	0.015	0.026	-	0.017	-	0.014	-	-
10	0.029	-	0.014	-	0.018	0.017	-	0.013	-	0.015	-	-
20	0.025	-	0.014	-	0.016	0.015	-	0.014	-	0.014	-	-
30	0.020	-	0.014	-	0.019	0.014	-	0.013	-	0.015	-	-
40	0.020	-	0.014	-	0.020	0.016	-	0.013	-	-	-	-
60	0.024	-	0.013	-	0.017	0.014	-	0.013	-	-	-	-
Station 78, 1985
1	0.010	-	0.009	-	0.008	0.008	-	0.010	-	-	0.010	-
10	0.009	-	0.010	-	0.007	0.011	-	0.006	-	-	0.009	-
20	0.009	-	0.009	-	0.007	0.008	-	0.007	-	-	0.010	-
30	0.010	-	0.009	-	0.007	0.007	-	0.007	-	-	0.011	-
B*	0.012	-	0.011	-	0.008	0.006	-	0.007	-	-	0.010	-
* Bottom-1.

E10 PAST TRENDS

• COD [mg l-1]

Stn.	1970	1973	1974	1975	1976	1977	1978	1979	1980	1981	1982	1983	1984	1985	1986
70	-	12	12	12	11	10	10	10	10	10	11	10	9	9	8
78	11	8	8	9	9	8	8	7	7	8	9	8	8	7	7

• Total-P [micro g l-1]

Stn.	1970	1973	1974	1975	1976	1977	1978	1979	1980	1981	1982	1983	1984	1985	1986
70	-	22	23	19	20	20	17	20	18	19	18	17	17	18	16
78	10	0	8	11	10	9	9	10	10	10	10	9	9	10	8

F. BIOLOGICAL FEATURES (Q)

F1 FLORA

• Emerged macrophytes
  Phragmites australis, Equisetum fluviatile, Glyceria maxima, Carex rostrata, C. vesicaria, C. acuta.
• Floating macrophytes
  Nuphar lutea, Nymphaea spp., Potamogeton natans, Polygonum amphibium.
• Submerged macrophytes
  Potamogeton gramineus, Elodea canadensis, Myriophyllum alterniflorum, Sparganium spp., Ceratophyllum demersum, Isoetes lacustris, I. echinospora.
• Phytoplankton
  Rhodomonas minuta, Cryptomonas spp., Asterionella formosa, Melosira italica v. tenuissima, Fragilaria spp., Tabellaria fenestrata, Aphanizomenon flos-aquae, Chlamydomonas spp., Chrysococcus spp.

F2 FAUNA

• Zooplankton
  Northern lake Asplanchna priodonta, Conochilus hippocrepis, C. unicornis, Kellicottia longispina, Keratella cochlearis, Polyarthra major, P. remata, P. vulgaris, Synchaeta sp., Trichocerca porcellus. Southern lake Tintinnopsis lacustris, Conochilus hippocrepis, C. unicornis, Kellicottia longispina, Keratella cochlearis, K. hiemalis, Gastropus stylifer, Collotheca sp., Polyarthra remata, P. vulgaris.
• Benthos
  Nothern lake Littoral zone (0-5 m) Gastropoda (Valvata piscinalis, Bithynia tentaculata), Bivalvia (Pisidium amnicum, P. casertanum), Oligochaeta (Limnodrilus hoffmeisteri, Peloscolex ferox), Crustacea *Asellus aquaticus, Pallasea quadrispinosa), Insecta (Ephemera vulgata, Cyrnus trimaculatus). Sublittoral zone (5-10 m) Gastropoda (Valvata piscinalis), Bivalvia (Pisidium amnicum, P. casertanum), Oligochaeta (Limnodrilus hoffmeisteri, Peloscolex ferox), Crustacea *Asellus aquaticus, Pallasea quadrispinosa), Insecta (Ephemera vulgata, Ablabesmyia longistyla). Profundal zone (15-100 m) Bivalvia (Pisidium casertanum, P. conventus), Oligochaeta (Stylodrilus heringianus, Limnodrilus hoffmeisteri), Crustacea (Pallasea quadrispinosa, Pontoporeia affinis), Insecta (Chaoborus flavicans, Procladius spp.). Southern lake Littoral zone (0-5 m) Gastropoda (Bathyomphalus contortus, Valvata piscinalis),Bivalvia (Pisidium amnicum, P. casertanum), Oligochaeta (Peloscolex ferox), Crustacea (Asellus aquaticus, Pallasea quadrispinosa), Insecta (Ephemera vulgata, Cyrnus trimaculatus). Sublittoral zone (5-10 m) Gastropada (Valvata piscinalis), Bivalvia (Pisidium amnicum, P. casertanum), Oligochaeta (Limnodrilus hoffmeisteri, Peloscolex ferox), Insecta (Ephemera vulgata, Oecetis lacustris). Profundal zone (15-85 m) Bivalvia (Pisidium casertanum, P. conventus), Oligochaeta (Lamprodrilus isoporus, Stylodrilus heringianus), Crustacea (Pallasea quadrispinosa, Pontoporeia affinis), Insecta (Procladius spp., Heterotrissocladius subpilosus).
• Fish
  Coregonus albula*, C. mulesum*, C. lavaretus*, Esox lucius*, Lota lota*, Stizostedion lucioperca, Perca fluviatilis*, Abramis brama*, Blica bjoerkna. * Economically important.

F3 PRIMARY PRODUCTION RATE [g C m-2]

Station 70, 1984-1985
Net production
Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann. total
-	-	-	-	3.2	10.5	5.4	9.3	4.1	-	-	-	32.7

F4 BIOMASS

	Wet weight
Station 70
- Phytoplankton, 1984-1986	1.0 [g m-2]
- Zooplankton, 1984-1985	12.4
- Bottom fauna, 1987
0-5 m	2
5-10 m	0.5
15-100 m	0.3
Station 78
- Phytoplankton, 1984-1986	0.4 [g m-3]

F5 FISHERY PRODUCTS

• Annual fish catch [metric tons]

ca. 1,200.

F6 PAST TRENDS

• Phytoplankton biomass [g (wet wt.) m-3]

Station 70
1969	1970	1975	1976	1977	1978	1980	1981	1982	1983	1984	1985	1986
1.2	1.3	1.0	1.0	1.5	0.50	0.82	0.92	0.98	0.74	0.95	1.4	0.67
Station 78
1969	1970	1979	1980	1981	1982	1983	1984	1985	1986
0.28	0.21	0.44	0.37	0.27	0.49	0.51	0.44	0.38	0.33

G. SOCIO-ECONOMIC CONDITIONS (Q)

G1 LAND USE IN THE CATCHMENT AREA

	Area [km2]	[%]
- Natural landscape
Woody vegetation	16,700	78
Swamp	1,600	8
Others	200	1
- Agricultural land	2,100	10
- Others	1,000	3
- Total	21,300	100

• Main types of woody vegetation: Pine 55%, spruce 35%, birch 10%.
• Main kinds of crops: Barley, oats, hay.
• Levels of fertilizer application on crop fields: Moderate.
• Trends of change in land use
  Swamps have been drained for forestry; cultivated land is diminishing.

G2 INDUSTRIES IN THE CATCHMENT AREA AND THE LAKE

	Gross product per year [t]	No. of establishments	Main products or major industries
- Primary industry			Grain, milk, meat
- Secondary industry			Timber, sawmill
	300,000	1	Pulp
	840,000	4	Paper
	2,000	1	Explosive

• Numbers of domestic animals in the catchment area
  Cattle 40,000, swine 40,000.

G3 POPULATION IN THE CATCHMENT AREA

	Population	Population density [km-2]	Major cities (population)
Urban	160.000
Rural	240,000	16	Jyvaskyla, Lahti
Total	400,000

H. LAKE UTILIZATION (Q)

H1 LAKE UTILIZATION

Source of water, navigation and transportation (500,000 [m3] of timber floating), sightseeing and tourism, recreation (swimming, sport-fishing, yachting) and fisheries.

H2 THE LAKE AS WATER RESOURCE

	Use rate
Domestic	2.3 [m3 sec-1](to capital area)
Industrial	0.1 (whole watershed until sea)
Power plant	1,300 [GWh yr-1]

I. DETERIORATION OF LAKE ENVIRONMENTS AND HAZARDS (Q)

I1 ENHANCED SILTATION

• Extent of damage: None.

I2 TOXIC CONTAMINATION

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

Station 70, 1981
	Bottom mud [ppm (dry wt.)]	Fish*[ppm (wet wt.)]	Main Sources
Hg	0.2	0.68	Industrial
PCB	0.2	0.02	Industrial
PCP	-	0.016	Industrial
* Pike muscle.

• Past trends

Fig. EUR-19-02
Hg concentrations of pikes (about 7 kg) in the three different basin of Lake Paijanne in 1970-1984.

• Supplementary notes
  Use of Hg-based additives against slime has been forbidden since 1968 in paper mills.

I3 EUTROPHICATION

• Nitrogen and phosphorus loadings to the lake [kg day-1]

1986
Sources	Industrial	Domestic	Agricultural	Natural	Total
T-N	1,270	1,800	ca. 600	ca. 11,000	ca. 15.000
T-P	135	40	ca. 20	ca. 300	ca. 500

• Supplementary notes
  Loadings have diminished after the 1960's due to wastewater purification and industrial (pulp mill) reconstruction.

I4 ACIDIFICATION

• Extent of damage: None.
• Past trends in hydrogen ion concentration in lake and rain water

	1973	1975	1977	1979	1981	1983	1985
Lake water	6.6	6.6	6.7	6.6	6.6	6.6	6.6
Rain water	-	4.8	4.6	4.6	4.6	4.5	4.6

J. WASTEWATER TREATMENTS (Q)

J1 GENERATION OF POLLUTANTS IN THE CATCHMENT AREA

c) Limited pollution with wastewater treatment.

J2 APPROXIMATE PERCENTAGE DISTRIBUTION OF POLLUTANT LOADS

	P[%]	N[%]
- Non-point sources	66	82
- Point sources	(34)	(18)
Municipal	7	10
Industrial	27	8
- Total	100	100

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: ca. 100%.
• Percentage of rural population with adequate sanitary facilities (on-site
  treatment systems): ca. 80%.
• Municipal wastewater treatment systems
  No. of tertiary treatment systems: ca. 30 (activated sludge with simultaneous P-coagulation).
• Industrial wastewater treatment systems
  No.of industrial wastewater treatment systems: 4 (activated sludge, mechanical (+chemical)).

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

M3 RESEARCH INSTITUTES ENGAGED IN THE LAKE ENVIRONMENT STUDIES

1. University bf Jyvaskyla, Institute for Environmental Research

N. SOURCE OF DATA

17. Questionnaire filled by Messrs. J. Niemi and A. Makela, National Board of Waters and Environment, Helsinki, Finland.