Lake Toba is the largest and the most famous in Indonesia located in the province of North Sumatra. Scientist belives that Lake Toba was once a gigantic volcanic mountain that erupted thousands of years ago. Thousand of years of rain filled the caldera with water, thus becoming a lake with an island called Samosir in the middle of the lake. Keywords: North Sumatra, lake, caldera volcano. Other famous lakes ini Indonesia: Lake Jatiluhur in West Java Province. Lake Poso in Central Sulawesi Province.
North Sumatra Province, Indonesia.
2:21-2:56N, 98:26-99:15E; 905 m above sea level.
Lake
Toba lies in the northern part of Barisan Mountain Range, which is volcanic
and traverses Sumatra Island from northwest to southeast as its backbone.
The laketrough is surrounded by precipitous cliffs
400-1,200 m high. Based on the topographic feature and the wide distribution
of volcanic ejecta around the lake, some geologists and valcanologists have
considered it to be a giant caldera or cauldron.
The water surface of L. Toba is 905 m above sea level
and about 1,100 km2 wide. The total area of the lake, including the areas of
Samosir and Paradapur Islands, amounts to 1,780 km2. The mountains around the
lake are called Batak Highlands. The only draining river from L. Toba, the
Asahan, flows southeastwards dissecting the gentle slopes of the pyroclastic
plateau.
|
Surface area [km2] |
1,100 |
|
Volume [km3] |
1,258 |
|
Maximum depth [m] |
529 |
|
Water level |
Unregulated |
|
Normal range of annual water |
|
|
level fluctuation [m] |
1.5 |
|
Catchment area [km2] |
3,440 |
D1 GEOGRAPHICAL
Sketch map: Fig. ASI-10-01.
Names of main islands: Samosir (640 km2) and Paradapur (7 km2).
Number of outflowing rivers and channels (name): 1 (Asahan R.).
D2 CLIMATIC
Climatic data at Parparean, 1961-1980
|
|
Jan |
Feb |
Mar |
Apr |
May |
Jun |
Jul |
Aug |
Sep |
Oct |
Nov |
Dec |
Ann. |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
Mean temp. [deg C] |
19.3 |
19.0 |
18.9 |
19.3 |
19.4 |
19.1 |
19.0 |
18.8 |
19.0 |
19.4 |
19.4 |
19.1 |
19.1 |
|
Precipitation [mm] |
100 |
105 |
115 |
132 |
124 |
102 |
83 |
110 |
148 |
174 |
182 |
178 |
1,732 |
Solar radiation: 15.7 MJ m-2 day-1.
Water temperature [deg C]
|
Station |
Surface |
|---|---|
|
Haranggaul |
27 |
|
Tigaras |
27 |
|
Tomok |
26 |
|
Simanindo |
27 |
|
Pangururan |
27 |
|
Nainggolan |
27 |
|
Prapat |
27 |
|
Porsea |
26 |
Freezing period: None.
Notes on water
mixing and thermocline formation
Mizuno observed an extremely homogeneous vertical distribution of water
temperature from the surface down to 300 m depth on 23 January 1976 (13).
Fig. ASI-10-01
E2 pH, 1979
|
Station |
Surface |
|---|---|
|
Lotung |
8.4 |
|
Situmeang |
7.9 |
|
Bukit |
8.4 |
|
Tongging I |
7.0 |
|
Tongging II |
7.9 |
|
Onan Runggu |
7.6 |
|
Prapat |
8.2 |
E4 DO [mg l-1], 1979
|
Station |
Surface |
|---|---|
|
Lotung |
6.7 |
|
Situmeang |
6.8 |
|
Bukit |
9.3 |
|
Tongging I |
6.3 |
|
Tongging II |
7.0 |
|
Onan Runggu |
7.0 |
|
Prapat |
8.0 |
E5 COD [mg l-1], 1979
|
Determined by KMnO4 method. |
|
|
Station |
Surface |
|---|---|
|
Haranggaul |
2.30 |
|
Prapat |
2.80 |
|
Mogang |
2.24 |
|
Onan Runggu |
2.15 |
|
Porsea |
2.06 |
|
Hashinggahan |
1.30 |
|
Tomok |
1.53 |
|
Sabulan |
1.72 |
|
Muara |
1.36 |
|
Balige |
1.24 |
E8 PHOSPHORUS CONCENTRATION
Total-P [mg l-1], 1979
|
Station |
Surface |
|---|---|
|
Haranggaul |
0.31 |
|
Hasinggahan |
0.32 |
|
Tomok |
0.66 |
E9 CHLORIDE CONCENTRATION [mg l-1], 1979
|
Station |
Surface |
|---|---|
|
Haranggaul |
8.6 |
|
Prapat |
8.3 |
|
Mogang |
10.1 |
|
Onan Runggu |
10.4 |
|
Porsea |
10.3 |
|
Hasinggahan |
11.8 |
|
Tomok |
11.0 |
|
Sabulan |
9.2 |
|
Muara |
9.6 |
|
Balige |
9.5 |
F1 FLORA
Emerged macrophytes: Nelumbo nucifera, Nymphaea sp.
Floating macrophytes:Eichhornia crassipes, Lemna minor, Azolla pinnata, Spirodella polyrhiza.
Submerged macrophytes:Potamogeton malaianus, P. polygonifolius, Myriophyllum spicatum, Ceratophyllum demersum, Hydrilla verticillata, Chara sp.
Phytoplankton:Amphora, Cocconema, Asterionella, Synedra, Gomphonema, Orthosira, Navicula,Mastogloia, Pleurosigma, Nitzschia, Genicularia, Botryococcus, Synechococcus,Anabaena, Oscillatoria.
F2 FAUNA
Zooplankton: Cyclops, Cladocera.
Benthos: Macrobrachium sintangensis, Brotia costula, Thiara scabra, Melanoidestuberculata, Melanoides granifera, Anentome helena, Lymnaea brevispira, L.rubiginosa, Physastra sumatrana, Corbicula tobae.
Fish: Tilapia mossambica, Aplocheilus pachax, Lebistes reticulatus, Osphronemus goramy, Trichogaster trichopterus, Channa striata, C. gachua, Clarias batrachus, C. nieuhofi, C. sp., Nemachilus fasciatus, Cyprinus carpio, Puntius javanicus, P. binotatus, Osteochilus nasselti, Lissochilus sp., Labeobarbus sora, Rasbora sp.
F4 BIOMASS
Submerged macrophytes [g (wet wt.) m-2]
|
Station |
Potamogeton sp. |
Myriophyllum spicatum |
Others |
Total |
|---|---|---|---|---|
|
Lotung |
2,470 |
130 |
<25 |
2,600 |
|
Onan Runggu |
2.800 |
150 |
0 |
2,950 |
|
Parbaloan Urat |
1,833 |
310 |
520 |
2,663 |
|
Tongging |
1,947 |
157 |
<25 |
2,104 |
|
Lumban Sitorus |
150 |
1,640 |
0 |
1,750 |
F5 FISHERY PRODUCTS
Annual fish catch
[metric tons]
1978: 2,820.
F6 PAST TRENDS
Annual fish catch [metric ton]
|
Year |
Production |
|||
|---|---|---|---|---|
|
Tilapia mossambica |
Cyprinus carpio |
Others |
Total |
|
|
1967 |
1,039 |
207.8 |
831.2 |
2,078 |
|
1976 |
- |
- |
- |
2,211 |
|
1977 |
- |
- |
- |
2,569 |
|
1978 |
2,175.1 |
4.6 |
640.2 |
2,820 |
F7 NOTES ON THE
REMARKABLE CHANGES OF BIOTA IN THE LAKE IN RECENT YEARS
Increasing: Tilapia mossambica. Decreasing: Cyprinus carpio.
G1 LAND USE IN THE CATCHMENT AREA
|
1981 |
||
|
|
Area [km2] |
[%] |
|---|---|---|
|
Natural landscape |
||
|
Grass (alang-alang) |
955 |
40.6 |
|
Scrub |
59.24 |
2.5 |
|
Forest |
159.66 |
6.8 |
|
Reforestation |
388.70 |
16.6 |
|
Regreening |
228.28 |
9.7 |
|
Agricultural land |
512.08 |
21.8 |
|
Plantation |
20.88 |
0.9 |
|
Others |
23.56 |
1.1 |
|
Total |
2,347.50 |
100 |
Main types of
woody vegetation:Tropical high mountain forest; Pinus merkusii forest;
Macadamia hildebrandii
forest.
Main types of herbaceous vegetation:Imperata cylindrica with Rhodomyrtus tomentos, Melastoma sp. and Gleichenia linearis.
Main kinds of crops: Rice, sweet potato, maize, vegetables.
Levels of fertilizer application on crop fields: Moderate.
G2 INDUSTRIES IN
THE CATCHMENT AREA AND THE LAKE
No information.
G3 POPULATION IN THE CATCHMENT AREA
|
1980 |
||||
|
|
||||
|
District |
Area[km2] |
Population |
Family |
Population density [km-2] |
|---|---|---|---|---|
|
Tapanuli Utara |
2,420.5 |
309,111 |
66,744 |
128 |
|
Tanah Karo |
63.0 |
3,901 |
731 |
62 |
|
Dairi |
45.0 |
9,011 |
1,810 |
200 |
|
Total |
2,528.5 |
322,023 |
69,285 |
127 |
H1 LAKE
UTILIZATION (Q)
Source of water,
navigation and transportation (amount of cargo in 1978: 1,922 metric tons),
sightseeing and tourism (no. of visitors in 1978: 44,625). recreation
(yachting), fisheries.
H2 THE LAKE AS WATER RESOURCE : No information.
I1 ENHANCED SILTATION
Extent of damage: Not serious.
I2 TOXIC
CONTAMINATION: No information.
I3 EUTROPHICATION: No information.
I4 ACIDIFICATION
Extent of damage: None.
J1 GENERATION OF POLLUTANTS IN THE CATCHMENT AREA
f) Measurable pollution without wastewater treatment.
J3 SANITARY FACILITIES AND SEWERAGES
Percentage of municipal population in the catchment area provided with adequate sanitary facilities (on-site treatment system) or public sewerage: None.
Percentage of rural population with adequate sanitary facilities (on-site treatment systems): None.
Municipal wastewater treatment systems: None.
Industrial wastewater treatment systems: None.
None.
Integrated management on Toba Lake catchment area.
Hydroelectric power plant under construction.
M1 NATIONAL AND LOCAL LAWS CONCERNED
Names of the laws (the year of legislation)
Act of the Republic of Indonesia No 4 concerning Basic Provisions for the Management of the Living Environment (1982)
State Regulation of the Republic of Indonesia No.29 on Environmental Impact Assessment (1986)
Responsible authorities
& (2) The State Minister for Population and Environment. Ministry of Home Affairs, Ministry of Public Works, Ministry of Forestry and Local (Provincial) Governments
M2 INSTITUTIONAL MEASURES
The State Minister for Population and Environment responsible for coordinating environmental managements
Ministry of Public Works responsible for lake utilization
Ministry of Home affairs responsible for regional development
Ministry of Forestry responsible for forest management and soil conservation
M3 RESEARCH INSTITUTES ENGAGED IN THE LAKE ENVIRONMENT STUDIES
Centre of Environmental Studies (University)
Institute of Hydraulic Engineering Agency of Resources and Development
Questionnaire filled by Dr. Herman Haerumen is, Ministry of State for Popula tion and Environment, Indonesia, based on the following literature (1)-(12).
Abdullah Angaedi (1980) Studi Perencanaan Perbaikan Keadaan Danau Toba,Suma tra Utara, PT. Indah Karya & Ministry of Public Works.
Asahan Development Authority (1984) Laporan Penyelesaian Pelaksanaan Pemban gunan Proyek Asahan.
Directorate of Forest Planning & Programme (1981) Pola Pengelolaan Catchmen t Area Danau Toba, Sumatra Utara. Ministry of Agriculture.
Hehanussa P. E. (1982) Tefra Toba. National Geology & Mining Institute. Na tional Institute of Sciences.
--- (1982) Penanggalan Radiometri Formasi Samosir Tefra Toba.National Geology & Mining Institute, National Institute of Sciences.
--- (1983) Tefra Toba disekitar Danau Toba, Sumatra Utara.National Geology & Mining Institute, National Institute of Sciences.
---, Fujii, S. & Yokoyama, T. (1983) New dates of fluvio-iacustrine deposits from Lake Toba, Indonesia.
Ibnu Fajar (1983) Laporan Penyelidikan Geologi Lingkungan Daerah Tadah Danau Toba, Sumatra Utara. Directorate of Environmental Planning of Geology.
--- (1984) Laporan Penyelidikan Geologi Tata Lingkungan Daerah Aliran Sungai Asahan, Sumatra Utara. Directorate of Environmental Planning of Geology.
University of Indonesia & Ministry of Public Works (1979) Survai Ekologi Danau Toba.
University of Sumatra Utara & The Office of State Minister for Development Supervision & Environment (1979) Komunitas, Lingkungan Perairan & Kehidupan Biologis Danau Toba, Sumatra Utara.
Yusron Loebis (1982) Penelitian Keseimbangan Tata Air Danau Toba.Institute of Hydraulic Engineering, Ministry of Public Works.
Mizuno, T. (1977) Water temperature and some other environmental factors in inland waters of tropical Asia. Suion no Kenkyu, 21 (1): 12-19 (in Japanese).
--- (1980) Lakes and Forests of Tropical Asia. 232 pp. Tokai Univ. Press, Tokyo (in Japanese).
1999 International Lake Environment Committee Foundation - ILEC. All rights reserved.