SHIKOTSU-KO (LAKE SHIKOTSU)

Looking southward across the lake

Photo.
Photo: Hokkaido Prefectural Government


A. LOCATION

  • Hokkaido, Japan.
  • 42:45N, 141:17E; 248.0 m above sea level.

B. DESCRIPTION

    Lake Shikotsu is a typical crater lake situated in the western part of the island of Hokkaido. The lake was created approximately 32,000 years ago, originally in a circular shape with a diameter of 12 km. Its present shape was achieved by the activity of surrounding volcanoes such as Mt. Eniwa, Mt. Fuppushi and Mt. Tarumai. The lake has a mean water depth of 266 m and the water volume (21 km3) is so large for its surface area that it rarely freezes in winter, despite an average temperature of -5deg C. Thus L. Shikotsu and neighboring L. Toya represent the northern boundary of distribution of non- freezing lakes in Japan.
    The lake is typically oligotrophic. A transparency value of 25 m was recorded in 1926. From 1927 to 1929, a large amounts of nitrogen and phosphorus were introduced into the lake to help the breeding of kokanee salmon (Oncorhynchus nerka) transplanted from L. Akan. Between 1973 and 1979, however, the maximum and average transparency still amounted to 38.5 m and 20 m, respectively, indicating that the water quality has been fairly stable during the past 50 years.
    In the Winter Olympic Games of 1972, a downhill race was held on Mt. Eniwa and the road system from the city of Sapporo was well improved. With the subsequent completion of lakeside roads, people now enjoy recreation, camping and field sports in the magnificent natural environs of Shikotsu-Toya National Park.


C. PHYSICAL DIMENSIONS (Q)

    Surface area [km2] 79
    Volume [km3] 20.95
    Maximum depth [m] 360.1
    Mean depth [m] 266.0
    Length of shoreline [km] 40.3
    Residence time [yr] 51.2
    Catchment area [km2] 223

D. PHYSIOGRAPHIC FEATURES

D1 GEOGRAPHICAL (Q)
  • Bathymetric map: Fig. ASI-16-01.
  • Names of main islands: None.
  • Number of outflowing rivers and channels (name): 1 (Chitose R.).

    Fig. ASI-16-01
    Bathymetric map (1).

D2 CLIMATIC
  • Climatic Data at Tomakomai*, 1973-1982 (2)
    Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann.
    Mean temp. [deg C] -5.0 -5.3 -1.7 3.8 9.7 14.2 18.6 19.6 15.6 9.8 2.7 -2.3 6.6
    Precipitation [mm] 98 76 144 128 103 145 131 299 215 260 145 92 1,767
    * Altitude 6 m.
  • Number of hours of bright sunshine: 1,982 hr yr-1.
  • Water temperature [deg C](Q)
    Station 1, 1981-1983
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 - - - - 5.5 12.0 - 20.1 - 12.4 7.7 5.8
    20 - - - - 5.0 9.3 - 10.0 - 12.4 7.8 5.1
  • Freezing period: None.

E. LAKE WATER QUALITY

E1 TRANSPARENCY [m](Q)
    Station 1, 1981-1983
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    - - - - 15.5 17.8 - 21.3 - 12.8 19.8 21.3
E2 pH (Q)
    Station 1, 1981-1983
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 - - - - 7.5 7.6 - 7.6 - 7.6 7.4 7.3
    20 - - - - 7.5 7.5 - 7.6 - 7.6 7.3 7.3
E3 SS [mg l-1](Q)
    Station 1, 1981-1983
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 - - - - 1 1 - 1 - <1 <1 <1
    20 - - - - 1 <1 - 1 - <1 <1 <1
E4 DO [mg l-1](Q)
    Station 1, 1981-1983
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 - - - - 12 11 - 8.6 - 9.8 10 12
    20 - - - - 11 11 - 11 - 10 10 11
E5 COD [mg l-1](Q)
    Station 1, 1981-1983
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 - - - - 0.5 0.6 - 0.6 - 0.9 0.6 0.6
    20 - - - - 0.5 0.7 - 0.7 - 0.9 0.6 0.7
E7 NITROGEN CONCENTRATION (Q)
  • Total-N [mg l-1]
    Station 1, 1981-1983
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 - - - - <0.05 <0.05 - <0.05 - <0.05 <0.05 <0.05
E8 PHOSPHORUS CONCENTRATION (Q)
  • Total-P [mg l-1]
    Station 1, 1981-1983
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 - - - - <.005 <.005 - <.005 - <.005 <.005 <.005
E10 PAST TRENDS: Fig. ASI-16-02.

    Fig. ASI-16-02
    Trend of transparency (3).


F. BIOLOGICAL FEATURES

F1 FLORA
  • Phytoplankton: Cyclotella spp., Sphaerocystis schroeteri.
F2 FAUNA
  • Zooplankton: Acanthodiaptomus pacificus, Daphnia longispina.
  • Benthos: Ephemeridae spp., Chironomidae spp., Phryganeidae spp.
  • Fish: Salvelinus leucomaenis, Oncorhynchus nerka, Cottus nozawae.
F5 FISHERY PRODUCTS
  • Annual fish catch [individuals]
    1983: 36,575.

G. SOCIO-ECONOMIC CONDITIONS

G1 LAND USE IN THE CATCHMENT AREA (Q)
    Area [km2] [%]
    Natural landscape
    - Woody vegetation 221.1 99.3
    Others 1.6 0.7
    Total 222.7 100.0
  • Main types of woody vegetation (4)
    Deciduous broadleaf forest (Betula ermanii, Quercus mongolica var. grosseserrata, Acer mono, Tilia japonica); evergreen conifer forest (Picea jezoensis, Abies sachalinensis); mixed evergreen conifer/deciduous broadleaf forest; scrub (Qvercus mongolica var. undulatifolia); evergreen conifer plantation (Picea jezoensis, Abies sachalinensis).
  • Levels of fertilizer application on crop fields: No information.
G2 INDUSTRIES IN THE CATCHMENT AREA AND THE LAKE (Q)
    1981
    Gross product per year [yen] No.of establishments Main products or major industries
    Primary industry
    FisheriesN.A. N.A. Kokanee salmon, rainbow trout
    Secondary industry
    Mining3,400,000 N.A. Gold, silver
    Tertiary industry N.A. 44 Hotels, souvenir shops
G3 POPULATION IN THE CATCHMENT AREA (Q)
    1982
    Population Population density [km-2] Major cities (population)
    Total 340 1.53 None

H. LAKE UTILIZATION

H1 LAKE UTILIZATION (Q)
    Sightseeing and tourism, recreation (sport-fishing, yachting) and fisheries.

H2 THE LAKE AS WATER RESOURCE (Q)
    The lake is not used as water source.

I DETERIORATION OF LAKE ENVIRONMENTS AND HAZARDS

I1 ENHANCED SILTATION: No information.

I2 TOXIC CONTAMINATION: No information.

I3 EUTROPHICATION: No information.

I4 ACIDIFICATION: No information.


J. WASTEWATER TREATMENTS

J1 GENERATION OF POLLUTANTS IN THE CATCHMENT AREA
    b) No sources of significant pollution.
J3 SANITARY FACILITIES AND SEWERAGES
  • Municipal wastewater treatment systems
    No. of secondary treatment systems: 1.

M. LEGISLATIVE AND INSTITUTIONAL MEASURES FOR UPGRADING LAKE ENVIRONMENTS

M1 NATIONAL AND LOCAL LAWS CONCERNED
    For national laws see "Biwa-ko".

N. SOURCES OF DATA

  1. Questionnaire filled by the Prefectural Government of Hokkaido.
  2. Japan Map Centre (ed.)(1982) Collection of Maps on Japanese Lakes (Technical Data of National Geographical Institute, D 1-No. 221). National Geographical Institute, Tsukuba.*
  3. Uchida, E., Asakura, T. & Kawamura, T. (ed.)(1983). Meteorological Data of Japan. 1060 pp. Toyo-keizaishinpo-sha, Tokyo.*
  4. Imada, K., Ito, T., Yoshizumi, Y., Awakura, T. & Yonekawa, T. (1980) Fluctuations of transparency, COD and several dissolved ions in Lake Shikotsu (1973-1979). Sci. Rep. Hokkaido Fish Hatchery, 35: 21-24.*
  5. Environment Agency (1981) The 2nd National Survey on the Natural Environment (Vegetation), Actual Vegetation Map. Japan Wildlife Research Centre, Tokyo.*

    6. * Printed in Japanese. The title are tentatively translated into English.