OGAWARA-KO (LAKE OGAWARA)

An aerial view of the northern half of the lake

Photo.
Photo: A.Kurata


A. LOCATION

  • Aomori Prefecture, Japan.

  • 40:47N, 141:20E; 0.0 m above sea level.


B. DESCRIPTION

    Lake Ogawara is a brackish water lake and is the eleventh largest lake in Japan. It has a surface area of 62.3 km2 with a mean depth of 11 m and a maximum depth of 25 m. There are four inflowing rivers including the Takase River, all coming from Hakkoda Mountain Range. The only outflowing river is also the Takase River.
    The lake was formed from a marine bay some 3,000 years ago by the recession of the sea and the formation of sand bar at its mouth,and has thereafter been gradually transformed into the present configuration. Many remains of human settlements in prehistoric and historic ages are found on hillsides around the lake, showing that the area was more densely inhabited when milder climates prevailed.
    Lake Ogawara, is brackish due to the invasion of seawater at times of high tide, but is going to be converted to a freshwater lake by the Lake Ogawara Comprehensive Development Project to serve as sources of drinking, industrial and irrigation water (Q).

C. PHYSICAL DIMENSIONS

    Surface area [km2] 62
    Volume [km3] 0.714
    Maximum depth [m] 25.0
    Mean depth [m] 11.2
    Water level Unregulated
    Normal range of annual water level fluctuation [m] 0.7
    Length of shoreline [km] 67.4
    Residence time [yr] 0.8
    Catchment area [km2] 800

D. PHYSIOGRAPHIC FEATURES (Q)

D1 GEOGRAPHICAL
  • Bathymetric map: Fig. ASI-40-01.

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

D2 CLIMATIC
  • Climatic data, 1985-1986

    Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann.
    Mean temp. [deg C]*1 -2.8 -1.8 3.0 9.0 13.2 15.9 19.7 24.9 20.8 13.6 7.5 2.8 10.5
    Precipitation [mm]*2 97 133 64 40 105 124 167 158 160 104 154 78 1,384
    *1 Station 1. *2 Sanya (ca. 20 km west from the lake).
  • Number of hours of bright sunshine: 1,950 hr yr-1.

  • Solar radiation: 12.0 MJ m-2 day-1.

    Fig. ASI-40-01
    Bathymetric map (Q).

  • Water temperature [deg C]

    Station 1
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0.5 1.2 - 1.9 7.3 14.0 14.9 18.4 23.7 22.2 17.3 11.8 4.8
    8.5 1.1 - 1.9 7.6 13.6 14.8 18.0 21.3 22.3 17.5 11.7 4.8
    16.0 1.2 - 1.9 7.3 12.3 13.3 14.5 17.3 17.5 16.0 11.7 5.0
  • Freezing period: December-March.

  • Mixing type: Dimictic.


E. LAKE WATER QUALITY (Q)

E1 TRANSPARENCY [m]
    Station 1, 1985-1986
    Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    3.1 - 3.5 2.8 3.9 4.3 3.8 3.3 3.3 4.0 3.5 4.3
E2 pH
    Station 1, 1985-1986
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0.5 7.4 - 7.6 7.6 7.6 7.6 7.7 7.8 7.8 7.6 7.5 7.5
    8.5 7.5 - 7.6 7.6 7.6 7.5 7.7 7.6 7.8 7.6 7.5 7.5
    16.0 7.5 - 7.6 7.5 7.5 7.4 7.2 7.1 7.0 7.2 7.6 7.5
E3 SS [mg l-1]
    Station 1, 1985-1986
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    .5 2 - 1 3 2 2 2 2 2 2 1 1
    8.5 2 - 2 4 3 2 2 2 2 1 2 6
    16.0 2 - 1 3 2 1 2 1 1 <1 1 1
E4 DO [mg l-1]
    Station 1, 1985-1986
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0.5 13 - 13 13 10 9.8 9.0 8.5 8.3 7.9 9.7 12
    8.5 13 - 12 12 10 9.1 8.6 7.6 7.9 8.6 9.6 12
    16.0 13 - 13 12 9.6 8.5 5.3 3.6 3.6 5.0 9.6 12
E5 COD [mg l-1]
    Station 1, 1985-1986
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0.5 3.1 - 3.3 3.1 2.4 2.8 2.3 2.9 2.5 2.6 2.5 2.6
    8.5 3.3 - 3.4 3.2 2.6 3.1 2.4 2.8 3.5 2.8 2.7 2.6
    16.0 3.3 - 3.7 3.2 2.4 2.8 1.9 1.9 3.1 2.8 2.5 3.1
E6 CHLOROPHYLL CONCENTRATION [micro l-1]
    Station 1, 1985-1986
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0.5 17.0 - 6.0 21.7 5.4 6.9 5.0 12.1 15.7 2.9 2.7 5.1
    8.5 15.0 - 6.4 19.9 4.6 3.3 4.5 9.9 12.7 2.7 2.4 4.1
    16.0 15.0 - 5.9 16.7 4.3 2.0 2.0 2.6 2.0 2.1 2.3 4.2
E7 NITROGEN CONCENTRATION
  • Total-N [mg l-1]

    Station 1, 1985-1986
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0.5 0.65 - 0.93 0.81 0.65 0.60 0.58 0.52 0.41 0.67 0.51 0.67
    8.5 0.91 - 0.91 0.82 0.71 0.62 0.59 0.57 0.54 0.62 0.53 0.66
    16.0 0.91 - 0.89 0.83 0.69 0.73 0.67 0.67 0.61 0.70 0.49 0.64
E8 PHOSPHORUS CONCENTRATION
  • Total-P [mg l-1]

    Station 1, 1985-1986
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0.5 0.029 - 0.031 0.014 0.013 0.017 0.014 0.016 0.016 0.010 0.022 0.031
    8.5 0.028 - 0.032 0.019 0.015 0.014 0.012 0.014 0.013 0.012 0.022 0.038
    16.0 0.034 - 0.031 0.013 0.012 0.021 0.024 0.017 0.013 0.028 0.023 0.036
E9 CHLORIDE CONCENTRATION [mg l-1]
    Station 1, 1985-1986
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0.5 840 - 695 693 651 640 617 491 532 640 747 768
    8.5 840 - 721 710 642 625 607 510 543 641 746 767
    16.0 846 - 718 710 679 733 997 1,136 1,121 1,048 750 808

F. BIOLOGICAL FEATURES (Q)

F1 FLORA
  • Emerged macrophytes
    Typha angustifola, T. latifolia, Zizania latifolia, Phragmites japonica, P. communis, Scirpus lacustris, Sparganium erectum, Sagittaria trifolia, Alisma canaliculatum, Menianthes trifoliata.
  • Floating macrophytes: Spirodela polyrhiza.

  • Submerged macrophytes
    Chara braunii, C. globularis, Myriophyllum verticillatum, M. spicatum, Ceratophyllum demersum, Ranunculus aquatilis var. pantothrix, Potamogeton perfoliatus, P. maackianus, P. crispus, Ruppia maritima.
  • Phytoplankton
    Achnantes microcephala, A. minutissima, Cocconeis placentula, Cyclotella sp., Diatoma elongatum, Merismopedia elegans.
F2 FAUNA
  • Zooplankton
    Sinocalanus tenellus, Keratella aculeate, Polyarthra platytera, Bosmina coregoni.
  • Benthos:Tubificidae, Corbicula japonica.

  • Fish
    Anguilla japonica*, Hypomesus pretiosus*, Salangichthys microdon*, Tribolodon hakonensis*, T. taczanowskii*, Cyprinus carpio*, Carassius auratus*, Mugil cephalus*, Acanthogobius flavimanus*, Lampetra japonica*, Lateolabrax japonicus. * Economically important.
F5 FISHERY PRODUCTS
  • Annual fish catch [metric tons]
    1986: 1,952.
  • Fishery products other than fish [metric tons]
    1986: 2,913.

G. SOCIO-ECONOMIC CONDITIONS (Q)

G1 LAND USE IN THE CATCHMENT AREA (1970)
    Area [km2] [%]
    Natural landscape
    - Woody vegetation 376.580 47.9
    Agricultural land
    - Crop field 161.921 20.6
    - Pasture land 2.326 0.3
    Others 244.873 31.2
    Total 785.700 100
  • Main types of woody vegetation
    Deciduous broad leaf forest (Fagus crenata, Quercus serrata, Prunus liveilleana, Ulmus davidiana var. japonica); conifer forest (Thujopsis dolabrata var. hondae); scrub (Alnus pendula, Coriaria japonica).
  • Main types of swamp vegetation
    Alder forest (Alnus japonica); sedge swamp (Carex spp., Moliniopsis japonica).
  • Main kinds of crops: Rice, yam and carrot.

  • Levels of fertilizer application on crop fields: Moderate.

G2 INDUSTRIES IN THE CATCHMENT AREA AND THE LAKE (1984)
    Gross product per year [mill. yen] No. of persons engafged Main productsor major industries
    Primary industry
    - Agriculture 41,937 17,025 Rice, yam, carrot
    - Fisheries 8,011 2,075 Corbicula (mussel), smelt
    Secondary industry 28,053 13,845
    Tertiary industry 90,728 37,040
  • Numbers of domestic animals in the catchment area
    Cattle 9,770, horse 6,410, swine 32,210, poultry 7,000.
G3 POPULATION IN THE CATCHMENT AREA (1984)
    Population Population density [km-2] Major cities (population)
    Urban 28,639 - Towada, Misawa
    Rural 49,757 -
    Total 78,396 98.0

H. LAKE UTILIZATION (Q)

H1 LAKE UTILIZATION
    Source of water, recreation (swimming, sport-fishing, yachting), fisheries.
H2 THE LAKE AS WATER RESOURCE (1977)
    Use rate [m3 sec-1]
    Domestic 0
    Irrigation 9.0
    Industrial 0
    Power plant 0

I. DETERIORATION OF LAKE ENVIRONMENTS AND HAZARDS (Q)

I1 ENHANCED SILTATION
  • Extent of damage: None.

I2 TOXIC CONTAMINATION
  • Present status: None.

  • Main contaminants and their concentrations

    Name of contaminants Concentration in water [ppm]
    Cd <0.004
    Cyanides <0.10
    Organic P <0.1
    Pb <0.02
    Cr6+ <0.04
    As <0.005
    Total Hg <0.0005
I3 EUTROPHICATION
  • Nitrogen and phosphorus loadings to the lake [t yr-1]

    Sources Industrial Domestic Agricultural Natural Total
    T-N 1.9 109.5 2,340.7 401.8 2,853.9
    T-P 0.1 29.1 439.4 17.2 485.8
I4 ACIDIFICATION
  • Extent of damage: None.


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
    [%]
    Non-point sources (agricultural, natural and dispersed settlements) 99.6
    Point sources (industrial) 0.4
    Total 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: 36%.
  • Municipal wastewater treatment systems
    No. of secondary treatment systems: 1 (activated sludge).

L. DEVELOPMENT PLANS (Q)

    Lake Ogawara is being planned to become a freshwater lake to be used as domestic, irrigation and industrial water sources within the framework of the 2nd Basic Development Project of Mutsu-Ogawara Region.

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

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

    1. For national laws see "Biwa-ko".
    2. Aomori Prefectural Pollution Control Ordinance (1972)
  • Responsible authorities

    1. Aomori Prefectural Government
  • Main items of control
    Cd, Cyanides, Organic P, Pb, Cr6+, As, Hg, Alkyl Hg, PCB
M2 INSTITUTIONAL MEASURES (the year of establishment)
  1. Environmental Pollution Control Centre of Aomori Prefecture (1971)
  2. The Construction Office for the Comprehensive Development of the Takase River, Tohoku Regional Construction Bureau, Ministry of Construction

N. SOURCES OF DATA

  1. Questionnaire filled by Aomori Prefectural Government, based on the following sources.
  2. Geogr. Survey. Inst., Ministry of Construction (1979) 1:50,000 Map of Misawa (1:50,000 Chikei-zu, Misawa).*
  3. Ibid. (1979) 1:50,000 Map of Hiranuma (1:50,000 Chikei-zu, Hiranuma).*
  4. Environment Agency (1987) The 3rd National Survey on the Natural Environment, Report of Lake Survey, Tohoku Region (Dai San-kai Shizen Kankyo Kiso Chosa, Kosho Chosa Hokokusho, Tohoku-ban).*
  5. The Construction Office for the Comprehensive Development of the Takase River, Tohoku Regional Construction Bureau, Ministry of Construction (1987) Four Seasons around Lake Ogawara (Shiki no Irodori Ogawara-ko).*
  6. Aomori Prefectural Government (1985) Results of Water Quality Monitoring in Public Water Bodies (Kokyo-yosuiiki Suishitsu Sokutei Kekka).*
  7. Aomori Prefectural Government (1986) Results of Water Quality Monitoring in Public Water Bodies (Kokyo-yosuiiki Suishitsu Sokutei Kekka).*
  8. The Construction Office for the Comprehensive Development of the Takase River Tohoku Regional Construction Bureau, Ministry of Construction (1987) Plants and Animals in Lake Ogawara (Ogawara-ko no Ikimonotachi).*
  9. Aomori Prefectural Government (1986) Trends of Fisheries in Aomori Prefecture (Aomoriken Gyogyo no Ugoki).*
  10. Aomori Prefectural Government (1977) Reports on Environmental Assessment related the 2nd Basic Development Plan of Mutsu-Ogawara Region (Mutsu Ogawara Kaihatsu Dai 2-ji Kihonkeikaku ni Kakawaru Kankyo Eikyo Hyoka Hokoku-sho).*
  11. Ministry of Agriculture, Forestry and Fisheries (1986) Statistics of Agricultural Workers Income (Seisan Nogyo Shotoku Tokei).*
  12. Ministry of Agriculture, Forestry and Fisheries (1985) Agricultural Census (Nogyo Sensasu).
  13. Aomori Prefectural Government (1987) Outlines of Economic Development in Aomori Prefecture (Keizai Kaihatsu Yoran).*
  14. Aomori Prefectural Government (1986) Comprehensive Plan of Sewerage Construction in River Watersheds; Takase River (Ryuikibetsu Gesuido Seibi Sogo Keikaku, Takasegawa Suiiki).*

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