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HO TAY (WEST LAKE)
A view from the eastern lakeshore
Photo: A.Kurata
A. LOCATION
- Hanoi City, Viet Nam.
- 21:04, 105:50E; 6.0 m above sea level.
B. DESCRIPTION
Ho (= lake) Tay is located in the western part of Hanoi City, and is the largest of the lakes of the Red River (Song Koi R.) delta. It is horseshoe- shaped and may be divided into two parts; the upper part is small and shallow with a surface area of 176 ha and the lower part is longer and deeper (237 ha). Its surface area has been progressively reduced, from 466 ha in 1960 to 413 ha in 1992, owing to the filling by human population encroaching the lake.
The lake had originally been a segment of the course of the Red River, but is now a semi-closed water body with only small inflow- and outflow-channels. It receives a daily amount of wastewater of about 10,000 m3 from surrounding urban areas. The increase of population around the lake resulted in moderate eutrophication. The growth of water hyacinth extensively covers the southern shore side of the lake, causing a serious trouble. Mud deposits 50-80 cm in thickness are found on the flat lake bottom.
Ho Tay provides the highest scenic spot in Hanoi. Lake-front open spaces are being developed for various recreational activities including fishing, boating and sightseeing for the citizens as well as for tourists (Q, 6).
C. PHYSICAL DIMENSIONS
| Surface area [km2] | 4.13 |
| Volume [km3] | 0.008 |
| Maximum depth [m] | 3.5 |
| Mean depth [m] | 1.7 |
| Normal range of annual water level fluctuation [m] | 0.8 |
| Length of shoreline [km] | 1.4 |
| Catchment area [km2] | 4 |
D. PHYSIOGRAPHIC FEATURES (Q)
D1 GEOGRAPHICAL
- Sketch map: Fig. ASI-62-1.
- Number of main islands: None.
- Number of outflowing rivers and channels (names) 4 (Xuan La, Nhat Tan, Trich Sai, Do).
Fig. ASI-62-1
Sketch map of the lake (Q).
D2 CLIMATIC
- Climatic data at Hanoi City (average for many years)
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Ann. | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Mean temp. [deg C] | 16.6 | 17.1 | 19.9 | 23.5 | 27.1 | 28.7 | 28.8 | 28.3 | 27.2 | 24.6 | 21.2 | 17.9 | 23.4 |
| Precipitation [mm] | 18 | 26 | 48 | 81 | 194 | 236 | 302 | 323 | 262 | 123 | 47 | 20 | 1,680 |
- Number of hours of bright sunshine: 1,640 hr yr-1.
- Solar radiation: 12.6 MJ m-2 day-1.
- Water temperature [deg C]
| Center of the lake, 1960 | ||||||||||||
| Depth [m] | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| S* | 21.2 | 20.6 | 26.0 | 30.5 | 26.5 | 29.2 | 30.5 | 31.7 | 27.3 | 27.3 | 24.0 | 18.0 |
* Surface.
- Freezing period: None.
- Mixing type: Polymictic.
- Notes on water mixing and thermocline formation: None.
E. LAKE WATER QUALITY (Q)
E1 TRANSPARENCY [cm]
| Center of the lake, 1969 | ||||||||||||
| Depth [m] | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 40 | - | 22 | 22 | 19 | 18 | 18 | - | - | - | - | - | |
1990: 25 cm.
E2 pH
| Center of the lake | ||||
| Depth | 1960 | 1965 | 1969 | 1990 |
|---|---|---|---|---|
| Surface | 7.6 | 7.8 | 7.7 | 8.0 |
E3 SS [mg l-1]
| Center of the lake | ||
| Depth | 1960 | 1990 |
|---|---|---|
| Surface | 60 | 80 |
E4 DO [mg l-1]
| Center of the lake | |||
| Depth | 1960 | 1965 | 1990 |
|---|---|---|---|
| Surface | 5.15 | 6.10 | 6.20 |
E5 COD [mg l-1]
Determined by KMnO4 method.
| Center of the lake, 1969 | ||||||||||||
| Depth [m] | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| S* | 20.5 | - | 26.4 | 41.6 | 41.6 | 41.0 | 46.6 | - | - | - | 36.8 | - |
* Surface.
E7 NITROGEN CONCENTRATION [mg l-1]
Center of the lake, 1969 (surface)
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| NH4-N | 0.60 | - | 0.63 | 0.37 | 0.37 | 0.41 | 0.37 | - | - | - | 0.80 | - |
| NO3-N | 0 | - | 0 | 0 | 0 | 0 | 0 | - | - | - | 0.06 | - |
- Total-N [mg l-1] Center of the lake, 1990 (surface): 0.10 0.95.
E8 PHOSPHORUS CONCENTRATION
- Total-P [mg l-1]
| Center of the lake | |||
| Depth [m] | 1960 | 1965 | 1990 |
|---|---|---|---|
| Surface | 0.71 | 0.50 | 0.76 1.36 |
E10 PAST TRENDS
No remarkable change.
F. BIOLOGICAL FEATURES (Q)
F1 FLORA
- Emerged macrophytes: Nelumbium speciosum.
- Floating macrophytes Eichhornia crassipes, Salvinia cucullata, Azolla pinnata, Lemna minor, Pistia stratiotes, Ipomoea reptans, Trapa bicornis, Nymphaea stellata, Limnanthemum indicum.
- Submerged macrophytes Vallisneria spiralis, Myriophyllum spicatum, Ceratophyllum demersum, Utricularia aurea, Hydrilla verticillata, Potamogeton crispus.
- Phytoplankton: 118 taxa. Dominant species: Cyanophyta (Microcystis aeruginosa, M. minima, M. pulverea), Chlorophyta (Scenedesmus quadricauda, S. obliquus, S. acuminatus, S. bicaudatus, Tetraedron regulare, T. minimum, Ankistrodesmus arcuatus, Actinastrum hantzschii, Chlorella spp.), Actinopodea (Rhaphidiophrys sp.).
F2 FAUNA
- Zooplankton: 43 species. Dominant species: Brachionus calyciflorus, B. falcatus, B. angularis, B. forficula. Asplanchna sieboldii, Trichocerca longiseta, T. cylindrica, Polyarthra vulgaris, Moina dubia, Ceriodaphnia rigaudi, Mesocyclops leuckarti, Thermocyclops taihokuensis.
- Benthos: 11 species. Cyclestheria hislopi, Grandidierella vietnamica, Branchiura sowerbyi, Branchiodrilus semperi, Limnodrilus hoffmeisteri, Macrobrachium nipponense, Chironomus sp., Tanypus sp., Sinotaia aeruginosa, Angulyagra polyzonata, Sinanodonta jourdyi.
- Fish: 33 species. Native fish species: Carassius auratus, Culter brevicauda, Toxabramis houdmeri, Hemiculter leucisculus, Rasborinus lineattus, Parasilurus asotus, Clarias fuscus, Anabas testudineus, Ophiocephalus maculatus, O. striatus, Misgurnus fossilis anguillicaudatus, Fluta alba.
Cultured fish species: Cyprinus carpio, Hypophthalmichthys molitrix, Aristichthys nobilis, Cirrhina molitorella, Ctenopharyngodon idella, Tilapia mossambica.
F3 PRIMARY PRODUCTION RATE [mg C l-1 day-1]
Lower part of the lake, 10-20 cm, 1976
| Net production | ||||||||||||
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Ann. |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| - | 2.10 | 2.35 | 2.69 | 2.16 | 2.54 | 2.12 | 3.79 | - | - | 1.04 | 0.89 | 2.18 |
| Dark respiration | ||||||||||||
| - | 0.63 | 0.84 | 0.58 | 0.54 | 0.79 | 0.75 | 0.83 | - | - | 0.26 | 1.00 | 0.69 |
| Gross production | ||||||||||||
| - | 2.73 | 3.29 | 3.27 | 2.70 | 3.30 | 2.87 | 4.62 | - | - | 1.30 | 1.89 | 2.88 |
F4 BIOMASS
- Biomass of phytoplankton (1990)
| Cell no.[106l-1] | Biomass [g m-3] | |
|---|---|---|
| Dry season | 7.15 | 3.49 |
| Wet season | 12.00 | 5.13 |
- Biomass of zooplankton
| Ind. no.[103 m-3] | Biomass [g m-3] | |
|---|---|---|
| 1960 | 25-170 | 0.01-1.0 |
| 1975-1976 | 25-90 | 0.2-1.3 |
| 1984 | 26-85 | 0.01-1.3 |
| 1988 | 20-68 | 0.2-1.2 |
- Biomass of zoobenthos
| Ind. no.[m-2] | Biomass [g m-2] | |
|---|---|---|
| 1960 | 640-3,149 | 2.2-9.2 |
| 1975-1976 | 917-5,256 | 7.1-17.5 |
| 1984 | 170-580 | 0.5-8.6 |
| 1988 | 110-200 | 1.2-6.0 |
F5 FISHERY PRODUCTS
- Annual fish catch (cultured fish) [metric tons] 1992: 332.
- Annual shrimp catch (Macrobrachium nipponensis)[metric tons] 1961: 35, 1962: 24.
F6 PAST TRENDS
- Past trend of annual fish catch [t yr-1]
| Year | Fish catch | Year | Fish catch |
|---|---|---|---|
| 1962 | 272 | 1981 | 261 |
| 1971 | 237 | 1983 | 224 |
| 1972 | 271 | 1984 | 246 |
| 1973 | 368 | 1985 | 340 |
| 1974 | 478 | 1986 | 369 |
| 1975 | 329 | 1987 | 388 |
| 1976 | 362 | 1988 | 380 |
| 1977 | 368 | 1989 | 296 |
| 1978 | 405 | 1990 | 256 |
| 1979 | 400 | 1991 | 329 |
F7 NOTES ON THE REMARKABLE CHANGES OF BIOTA IN THE LAKE IN RECENT YEARS
Submerged and floating macrophytes (except Eichhornia) and native fish species greatly decreased. Significant decrease of zoobenthos, particularly Mollusca and Grandidierella vietnamica; no apparent changes in fish production.
G. SOCIO-ECONOMIC CONDITIONS (Q)
G1 LAND USE IN THE CATCHMENT AREA (1990)
| Area [ha] | [%] | |
|---|---|---|
| Natural landscape | ||
| - Woody vegetation | 20 | 5 |
| - Herbaceous vegetation | 30 | 7.5 |
| - Swamp | 50 | 12.5 |
| Agricultural land | ||
| - Crop field | 100 | 25 |
| Residential area | 200 | 50 |
| Total | 400 | 100 |
- Main kinds of crops: Fruit trees, vegetables and ornamental plants.
- Levels of fertilizer application on crop fields: Heavy.
- Trend of change in land use in recent years Expansion of human settlement area.
G2 INDUSTRIES IN THE CATCHMENT AREA AND THE LAKE (1990)
| No. of persons engaged | |
|---|---|
| Primary industry | |
| - Crop production | 2,000 |
| - Fisheries | 150 in Ho Tay Fish Farming Company 300 private |
| - Aquarium fish production | 20 (families) |
| Secondary industry | |
| - Artisanal and light industry | 2,000 |
| Tertiary industry | 300 |
- Number of domestic animals in the catchment area Cattle 100, swine 4,000, poultry over 20,000.
G3 POPULATION IN THE CATCHMENT AREA (1990)
| Population | Population density [km 2] | Major cities | |
|---|---|---|---|
| Urban | 15,000 | - | Hanoi* |
| Rural | 5,000 | ||
| Total | 20,000 | 5,000 |
* Not all the city area is included in the catchment area.
H. LAKE UTILIZATION (Q, 6)
H1 LAKE UTILIZATION
Source of water, irrigation, fisheries, tourism and recreation (swimming and yachting).
I. DETERIORATION OF LAKE ENVIRONMENTS AND HAZARDS (Q, 6)
I1 ENHANCED SILTATION
- Extent of damage: Not serious.
I2 TOXIC CONTAMINATION
- Present status Detected but not serious (Hg in wastewater of paper mill).
I3 EUTROPHICATION
- Nuisance caused by eutrophication Unusual algal bloom; foul smell of tap water taken from inflowing channels.
J. WASTEWATER TREATMENTS (Q)
J1 GENERATION OF POLLUTANTS IN THE CATCHMENT AREA
(d) Measurable pollution with limited wastewater treatment.
K. IMPROVEMENT WORKS IN THE LAKE (Q, 6)
None.
L. DEVELOPMENT PLANS (Q, 6)
Many hotels, restaurants, tourism services and villas have recently been built without environmental impact assessment (EIA).
M. LEGISLATIVE AND INSTITUTIONAL MEASURES FOR UPGRADING LAKE ENVIRONMENTS (Q)
M1 NATIONAL AND LOCAL LAWS CONCERNED
None.
- Responsible authorities
- Hanoi City authorities
- Ho Tay Fish Farming Company
M2 INSTITUTIONAL MEASURES
- Hanoi City Committee for Protection of Environment
M3 RESEARCH INSTITUTES ENGAGED IN THE LAKE ENVIRONMENT STUDIES
Laboratory of Ecology, Faculty of Biology, Hanoi University
N. SOURCES OF DATA
Questionnaire filled by Dr. Mai Dinh Yen, Laboratory of Ecology, University of Hanoi, Hanoi.
- Dang Ngoc Thanh, Mai Dinh Yen & Dao van Tien (1961) Preliminary investigation on hydrobiological and aquatic resources of Lake Ho Tay (Hanoi). Presented at West Pacific Fisheries Congress, Ulan Bator.
- Thai Ba Ho (1970) Results of study on physico-chemical characteristics of wastewater of Hanoi City during the years 1968 69. Report of Scientific Team of Hanoi City.
- Nguyen Trong Nho, Vu Thi Tam & Vu Van Tan (1979) First data obtained on biological productivity of phytoplankton of Lake Ho Tay (Hanoi), Journal of Biology, 1: 11 15.
- Mai Dinh Yen (1980) Some ecological data of five main types of freshwater ecosystems in the North of Vietnam (unpublished).
- Vu Dang Khoa et al. (1991) Scientific basis for improving the fish production of Lake Ho Tay. Report of Research Program of Scientific Committee of Hanoi City.
- The editor s observation.
* Publications cited were printed in Russian. The titles are tentatively translated into English.
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