OGAWARA-KO (LAKE OGAWARA)

An aerial view of the northern half of the lake


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

17. Questionnaire filled by Aomori Prefectural Government, based on the following sources.
1. Geogr. Survey. Inst., Ministry of Construction (1979) 1:50,000 Map of Misawa (1:50,000 Chikei-zu, Misawa).*
2. Ibid. (1979) 1:50,000 Map of Hiranuma (1:50,000 Chikei-zu, Hiranuma).*
3. 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).*
4. 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).*
5. Aomori Prefectural Government (1985) Results of Water Quality Monitoring in Public Water Bodies (Kokyo-yosuiiki Suishitsu Sokutei Kekka).*
6. Aomori Prefectural Government (1986) Results of Water Quality Monitoring in Public Water Bodies (Kokyo-yosuiiki Suishitsu Sokutei Kekka).*
7. 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).*
8. Aomori Prefectural Government (1986) Trends of Fisheries in Aomori Prefecture (Aomoriken Gyogyo no Ugoki).*
9. 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).*
10. Ministry of Agriculture, Forestry and Fisheries (1986) Statistics of Agricultural Workers Income (Seisan Nogyo Shotoku Tokei).*
11. Ministry of Agriculture, Forestry and Fisheries (1985) Agricultural Census (Nogyo Sensasu).
12. Aomori Prefectural Government (1987) Outlines of Economic Development in Aomori Prefecture (Keizai Kaihatsu Yoran).*
13. Aomori Prefectural Government (1986) Comprehensive Plan of Sewerage Construction in River Watersheds; Takase River (Ryuikibetsu Gesuido Seibi Sogo Keikaku, Takasegawa Suiiki).*

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