KIZAKI-KO (LAKE KIZAKI)

Yachting on the lake in summer


Photo: A. Kurata

A. LOCATION

• Nagano Prefecture, Japan.


• 36:33N, 137:50E; 764 m above sea level.

B. DESCRIPTION

The so-called "Nishina Three Lakes", L. Aoki, L. Nakatsuna and L. Kizaki, are a chain of tectonic lakes about 30,000 years old. They are situated at the eastern foot of the Japanese Northern Alps along the remarkable tectonic zone or Fossa Magna which traverses the main island (Honshu) of Japan. L. Aoki (maximum depth 58 m) is oligotrophic, L. Nakatsuna (maximum depth 12 m) is eutrophic, and L. Kizaki (maximum depth 29.5 m) is mesotrophic, although these lakes are arranged linearly from north to south along the same water system. The trophic level of the water is apparently inversely correlated with depth. Since such nutritional dynamics lend themselves to comparative limnology, many studies have been carried out on the Nishina Three Lakes since the first voluminous work by A. Tanaka, "Studies on the Lakes of the Japanese Northern Alps (1930)".
The water level of L. Aoki in winter has been lowered by about 20 m since 1954, owing to the use of its water for power generation. Provision was also made to introduce cold water from a neighboring river running down from the Japanese Alps, thus radically changing the aquatic environment of L. Aoki. The water level of L. Kizaki also becomes lower by about 3 m in winter, and is recovered in spring by channeling water from L. Aoki. The transparency in L. Kizaki averaged about 5 m until 1950, but decreased to approximately 3 m since 1970. From the end of the 1970's, Anabaena has bloomed annually in July- August, and the coloration of surface water has also become frequent due to the increase of microorganisms which graze upon Anabaena. These evidences suggest that the trophic level of this lake has recently changed from mesotrophic to eutrophic.

C. PHYSICAL DIMENSIONS (Q)

Surface area [km2]	1
Volume [km3]	0.025
Maximum depth [m]	29.5
Mean depth [m]	17.9
Water level	Regulated
Normal range of annual water
- level fluctuation [m]	3
Length of shoreline [km]	7.0
Residence time [yr]	0.5
Catchment area [km2]	22

D. PHYSIOGRAPHIC FEATURES

D1 GEOGRAPHICAL

• Bathymetric map: Fig. ASI-32-01.


• Number of outflowing rivers and channels (name): 1 (Nougu R.).

D2 CLIMATIC

• Climatic data at Aoki-ko, 1972-1980 (Q)

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann.
Mean temp. [deg C]	-3.5	-3.4	0.2	7.1	13.0	17.1	21.0	21.5	17.1	11.0	4.8	-0.5	8.8
Precipitation [mm]	184	171	148	160	136	218	180	179	164	112	144	157	1,953

Fig. ASI-32-01
Bathymetric map (1).

• Water temperature [deg C](5)

Station 1, 1985
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0.5	-	-	-	11.5	14.4	19.7	20.7	28.0	21.1	16.1	9.9	5.9
29	-	-	-	6.8	5.4	5.7	5.8	5.8	5.9	5.9	5.9	5.7

• Freezing period: January-March.


• Mixing type: Dimictic.


• Notes on water mixing and thermocline formation
  The thermocline is formed from May to October.

E. LAKE WATER QUALITY

E1 TRANSPARENCY [m](5)

Station 1, 1985
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
	-	-	-	2.5	4.0	3.5	3.5	6.5	7.5	7.5	10	5.0

E2 pH (5)

Station 1, 1985
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0.5	-	-	-	7.4	7.3	9.2	7.2	7.5	7.4	7.7	7.8	6.8
29	-	-	-	6.6	6.6	6.5	6.4	7.6	6.4	6.5	7.8	6.8

E3 SS [mg l-1](5)

Station 1, 1985
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0.5	-	-	-	<1	2	2	2	1	3	2	2	1
29	-	-	-	<1	2	<1	4	4	4	3	4	2

E4 DO [mg l-1](5)

Station 1, 1985
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0.5	-	-	-	11	10	9.9	9.6	8.5	8.6	9.4	9.5	8.9
29	-	-	-	8.5	8.6	6.1	3.1	0.8	0.9	1.0	0.2	6.2

E5 COD [mg l-1](5)

Determined by KMnO4 method.

Station 1, 1985
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0.5	-	-	-	2.3	2.1	3.0	1.2	1.6	1.3	<0.5	1.0	0.9
29	-	-	-	1.5	1.1	1.8	1.3	0.8	1.1	1.6	2.3	1.0

E6 CHLOROPHYLL CONCENTRATION [micro l-1](Q)

Station 1, 1981
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0	-	-	-	-	0.5	-	0.5	2.1	6.4	7.8	0.4	2.1
2	-	-	-	-	1.0	-	1.8	1.7	6.0	14.6	1.0	2.0
5	-	-	-	-	0.9	-	4.4	0.9	1.8	1.3	1.2	2.2
10	-	-	-	-	0.5	-	2.7	0.9	0.5	0.6	0.7	2.1
20	-	-	-	-	0.5	-	1.0	0.3	0.4	1.1	0.5	1.0

E7 NITROGEN CONCENTRATION (5)

• Total-N [mg l-1]

Station 1, 1985
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0.5	-	-	-	0.47	0.49	0.36	0.27	<0.29	0.19	0.14	0.15	0.44
29	-	-	-	0.71	0.72	0.90	0.88	0.58	0.56	0.44	1.2	0.47

E8 PHOSPHORUS CONCENTRATION (5)

• Total-P [mg l-1]

Station 1, 1985
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0.5	-	-	-	.012	.015	.007	.005	.035	.006	.005	.004	.008
29	-	-	-	.009	.009	.015	.011	.005	.010	<.003	.057	.008

E10 PAST TRENDS: Fig. ASI-32-02.

Fig. ASI-32-02
Trend of transparency (2).

F. BIOLOGICAL FEATURES

F1 FLORA (Q)

• Emerged macrophytes
  Nelumbo nucifera, Zizania latifolia, Eleocharis kurokuwai, Phragmites communis.
• Floating macrophytes: Nymphoides peltata, N. tetragona, Trapa japonica.


• Submerged macrophytes
  Ceratophyllum demersum, Hydrilla verticillata, Elodea nuttallii.
• Phytoplankton: Anabaena sp., Fragilaria crotonensis, Melosira sp.

F2 FAUNA (Q)

• Zooplankton
  Conochilus sp., Cyclops vicinus, Alona quadrangularis, Colurella sp.
• Benthos
  Chironomus plumosus, Chaoborus sp., Tubifex sp.,m Tanytarsus sp.
• Fish
  Leuciscus hakonensis, Zacco platypus, Hypomessua transpacificus, Carassius sp.

F5 FISHERY PRODUCTS

• Annual fish catch [metric tons]: ca. 10.

G. SOCIO-ECONOMIC CONDITIONS

G1 LAND USE IN THE CATCHMENT AREA (3)

	Area [km2]	[%]
Natural landscape
- Woody vegetation and	18.61	84.4
- Herbaceous vegetation
Agricultural land	1.12	5.1
Residential area	0.65	2.9
Others	1.67	7.6
Total	22.05	100.0

• Main types of woody vegetation (4)
  Deciduous broadleaf forest (Fagus crenata, Quercus serrata, Q. mongolica var. grosseserrata, Betula ermanii); evergreen conifer forest (Thuja standishii, Tsuga diversifolia, Abies marieseii); conifer plantation (Larix kaempferi, Cryptomeria japonica).
• Main types of herbaceous vegetation: Grassland and alpine plant communities.

G3 POPULATION IN THE CATCHMENT AREA (3)

1980
	Population	Population density [km-2]	Major cities (population)
Total	1,500	63	None

H. LAKE UTILIZATION

H1 LAKE UTILIZATION (Q)

Fisheries, tourism and recreation (swimming, sport-fishing, yachting).

I. DETERIORATION OF LAKE ENVIRONMENTS AND HAZARDS (Q)

I3 EUTROPHICATION

• Nitrogen and phosphorus loadings to the lake [t yr-1](3)

Sources	Industrial	Domestic	Agricultural	Natural	Others	Total
T-N	0.66	0.96	3.42	5.87	3.23	14.14
T-P	0.05	0.16	0.16	0.23	0.19	0.79

I4 ACIDIFICATION

• Extent of damage: None.

J. WASTEWATER TREATMENTS (Q)

J3 SANITARY FACILITIES AND SEWERAGE

• Municipal wastewater treatment systems: Not present.

M. LEGISLATIVE AND INSTITUTIONAL MEASURES FOR UPGRADING LAKE ENVIRONMENTS

M1 NATIONAL AND LOCAL LAWS CONCERNED

• Names of the laws (the year of legislation)


1. For national laws see "Biwa-ko".
2. Prefectural Government Code for Prevention of Public Nuisances
• Responsible authorities


1. Nagano Prefectural Government

N. SOURCES OF DATA

17. Questionnaire filled by Nagano Prefectural Government.
1. Horiuchi, S., Anbe, Y. & Obata, H. (1963) Survey of Lake Kizaki basin with an ultrasonic detector (Gyogun-tanchiki ni yoru Kizaki-ko no kobon chosa). J. Geogr. (Chigaku Zasshi), 72: 126-130.*
2. Funakoshi, M. (Shinshu University) Personal communication.
3. Nagano Prefecture Anti-Public Nuisance Management Association (1985) Study on Nishina-sanko Water Quality Improvement Measures.
4. Nagano Prefecture Vegetation Map Study Group (1975) Vegetation Map and Phytosociological Study of Nagano Prefecture, Vol. 2 (Nagano-ken no Shokusei-zu, Shokubutsushakaigakuteki Kenkyu, 2). Nagano Prefectural Government, Nagano.*
5. Nagano Prefectural Government (1985) Results of Water Quality Monitoring in Public Water Bodies (Kokyo-suiiki Suishitsu Sokutei Kekka).*

* Printed in Japanese. The titles are tentatively translated into English with original titles in romanized in parentheses.