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National Survey
Lake and Marsh Survey
Survey Sequence and Effective Years
(All years are fiscal years)		 data Result list (Japanese only except )
2nd survey
1979		   Outline of the National Survey on the Natural Environment (Vegetation, Lakes and Rivers)
Report of the National Survey on the Lake and Marsh
3rd survey
1985		   Report of the National Survey on the Lake and Marsh
Report of the National Survey on the Lake and Marsh (Appendix)
Natural Environment Map (1:200,000) (every all pref.)
4th survey
1991		   Report of the National Survey on the Lake and Marsh
Report of the National Survey on the Lake and Marsh (Appendix)
List of the surveyed Lake and Marsh
Natural Environment Map (1:200,000) (every all pref.)
How To Read This Display
  1. Survey Objectives
 This survey of the water quality, lakeshore alteration, freshwater fish, etc., in Japan's lakes and marshes was done to determine the extent of loss of natural qualities and thus contribute to their conservation.
  2. Survey Content and Methods

 Lakes and marshes were selected from among those having in principal 1ha or more of fresh water area. The 2nd survey looked at 487 lakes and marshes. The 3rd surveyed 483 (*1), and the 4th, 480 (*2).

*1 5 lakes and marshes from the 2nd survey disappeared, and one was newly added.
*2 3 lakes or marshes from the 3rd survey no longer remained in their original shape.

 The survey of the selected lakes and marshes was done under the following three headings.

(1) General Information
 To get general information on the target lakes and marshes, 20 items were checked, including origin, area, water quality and maximum depth.

(2) Transparency
 Transparency, water temperature, air temperature, pH and DO were checked. In the 4th survey, EC and alkali levels were added.

(3) Alteration
 To get an idea of the extent of alterations of lakes and marshes, lakeshore changes were classified under the following headings: natural lakeshore; semi-natural lakeshore; artificial lakeshore; water surface (in-and-out-river flow). Land use of lakeshore was classified as follows: natural; agricultural; urban-industrial and other; water surface. The status of conservation area designation was also examined.

(4) Freshwater fish fauna
 In lakes and marshes selected by the Environment Agency(*), (61 in the 2nd survey; 60 in the 3rd, excluding Shinryo Pond), 5 items were checked, including fish fauna records and amount of catch.

(5) Plankton (done only in the 4th survey)
 A survey of phytoplankton and zooplankton was done in the above-selected lakes and marshes.
  3. Survey Results
(1) General Information
 The total surface area of target lakes and marshes was 2,374.37 km2. The size of the various lakes depends on their origin. The biggest lakes and marshes in terms of various aspects of dimension are shown as follows:
Lake and Marsh Size Values
Height above sea level Ni no Ike (Nagano Pref.) 2905m
Area Lake Biwa (Shiga Pref.) 669.20km2
Maximum Depth Tazawa Lake (Akita Pref.) 423.0m
Av. Depth Tazawa Lake (Akita Pref.) 280.0m
Volume Lake Biwa (Shiga Pref.) 27.5km3
Lakeshore Length Lake Biwa (Shiga Pref.) 241.2km


(2) Transparency
 There were 13 lakes nationwide with transparency greater than 10m deep. The overwhelming majority of lakes and marshes had transparency of under 5m. The 3 clearest lakes were Mashu Lake (28.0m), Kuttara Lake (22.0m) and Akanuma (18.2m). There were many caldera lakes, and the average of transparency was 10m. In the nutrient lake category, oligotrophic lakes and acidotrophic lakes had high transparency.

(3) Alteration
 Total lakeshore length was 3,184.2km. Of this total, 56.6% remained in the natural state, 12.4% were semi-natural, artificial lakeshore accounted for 30.3% and open water (in-and-out-river flow), 0.7%.
49 lakes and marshes had artificial or urbanized lakeshores of over 10% of their total. Inba Marsh, with 11.5km, had the longest extent of artificial lakeshore. Naganuma Marsh had the greatest length of urbanized lakeshore - 4.9km.

 There were 210 unchanged lakes and marshes, but 195 of these had lakeshore less than 5km long, suggesting that the smaller a lake or marsh is, the less likely it is to have been affected by human activity.

(4) Freshwater fish fauna
 The average number of fish species per lake was 25. Hamana Lake (257 species) and Nakaumi Lake (96 species) showed the greatest diversity. The 11 lakes with the greatest diversity of fishes, except for Lake Biwa, were brackish water lakes, and the origin was lagoon.
 The number of lakes with introduced fish species changed little between the 3rd and 4th surveys. The survey showed that introduced species existed in 1/4 to 1/3 of lakes researched.  These included Rainbow Trout in 18 lakes, Grass Carp in 14 lakes, and Black Bass in 20 lakes.

(5) Plankton
 Large numbers of phytoplankton species were found in Kamo Lake (23 species), and Shojin, Biwa and Ikeda Lakes (16 species). Many species of zooplankton exist in Kamo Lake (19 species), Lake Biwa (16 species) and Ikeyama Lake (11 species). It is clear that eutrophic lakes support the greatest populations of phytoplankton and zooplankton.
Alteration of Lakeshore: Length(km) ( ): Percentage
Survey Year No.of Lakes Total Natural Semi-Natural Artificial Rivers
2nd Survey (1979) 476 3142.0
(100.0)		 1879.9
(59.8)		 322.2
(10.3)		 918.8
(29.2)		 21.1
(0.7)
3rd Survey (1985) 476 3168.4
(100.0)		 1862.9
(58.8)		 375.0
(11.8)		 909.6
(28.7)		 20.9
(0.7)
4th Survey (1991) 476 3183.4
(100.0)		 1803.0
(56.6)		 393.7
(12.4)		 965.2
(30.3)		 21.5
(0.7)
Change, 2nd - 3rd Survey -   - 1.0 1.5 - 0.5 0.0
Change, 3rd - 4th Survey -   - 2.2 0.6 1.6 0.0

(Note 1) 476 of the target lakes and marshes have been surveyed for changes three times.
(Note 2) Differences in total lakeshore length result from re-survey results.
(Note 3) -:shows minus change
Unchanged Lakes With More Than 5km of Lakeshore
Rank Lake Name Prefecture Origin Type Lake-shore
length (km)		 Protected Area
1 Mashu Hokkaido Caldera O 19.8 NP
2 Yudo Marsh Hokkaido Lagoon D 17.8  
3 Onne Hokkaido Lagoon O 13.9 PP
4 Panke Marsh Hokkaido Dam O 12.4 NP
5 Mushuga Fukui Dam O 9.7 QNP
6 Nagabushi Marsh Hokkaido Lagoon E 8.6  
7 Panke Marsh (Teshio) Hokkaido Lagoon D 7.5 NP
8 Chimikep Marsh Hokkaido Dam E 7.4  
9 Junsai Marsh Hokkaido Other D 7.0 NP
10 Naganuma Hokkaido Other D 6.4 NP
11 Poro Marsh Hokkaido Lagoon D 6.0  
12 Tachikobu Marsh Hokkaido Lagoon O 5.8 NP
12 Penke Marsh (Teshio) Hokkaido Lagoon D 5.8 NP
14 Horokayanto Marsh Hokkaido Lagoon D 5.7  
15 Benten Marsh Hokkaido Lagoon M 5.2  


"Other" lake origin means origins other than fault lake, volcanic, dam, or lagoon.
Nutrient type: E (eutrophic), M (mesotrophic), O (oligotrophic), D (Dystrophic)
Protected Areas: NP (national parks), QNP (quasi- national parks), PP (prefectural natural parks)


Definition of Lakeshore Categories
Classification Content
Natural lakeshore A 20m section of waterline and adjacent land with no man-made changes
Semi-natural lakeshore Natural waterline exists but man-made changes are evident within 20m sections.
Artificial The waterline is man-made.


1) The area of a lake or marsh for this survey is the high-water extent of still water surface. Inlet and
outlet rivers are excluded.
2) "Waterline" means where the water level touches land at high water.
3) "Lakeshore" includes the land area 100 meters inland from the waterline.
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*) The organization was changed to the Ministry of Environment in 2000.