Survey Sequence and Effective Years

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River 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 River
3rd survey 1985		Report of the National Survey on the River Report of the National Survey on the River (Appendix) List of the surveyed River Natural Environment Map (1:200,000) (every all pref.)
4th survey 1992		Report of the National Survey on the River Report of the National Survey on the River (Appendix) List of the surveyed River Natural Environment Map (1:200,000) (every all pref.)
5th survey 1998		Report of the National Survey on the River

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1. Survey Objectives

For rivers in Japan, measures have been taken against the deterioration in water quality. However, surveys have not necessarily been conducted sufficiently in a continual and systematic manner, to tackle the deterioration in biota, the loss of recreation & relaxation sites for residents and other problems caused by the construction of dams, embankment work, land reclamation & underdrain work at rivers in urban districts and other radical alterations.

For this reason, the 2nd and 3rd National Surveys on the Natural Environment were conducted in 1979 and 1985, respectively, to study the current status of main channels of first-class rivers across Japan, and the 4th National Survey in 1992 to study the main channels of major second-class rivers and tributaries of first-class rivers. The 5th National Survey conducted in 1998 targeted the main channels of first-class rivers studied in the 3rd National Survey again, to investigate the profile of the rivers and the alteration status of riverfronts. It also investigated the alteration status of rivers in which the wilderness was preserved in catchment areas ("wilderness watershed areas") sampled in the 2nd-4th National Surveys.

**Survey Items and Circumstances**
Survey Year	targeted rivers	Survey Items
2nd Survey (1979)	first-class rivers throughout Japan	River alteration status, wilderness watershed areas, fish fauna
3rd Survey (1985)	first-class rivers throughout Japan	River alteration status, wilderness watershed areas, fish fauna
4th Survey (1992)	second-class rivers throughout Japan	River alteration status, wilderness watershed areas, fish fauna, river profile
5th Survey (1998)	first-class rivers throughout Japan	River alteration status, wilderness watershed areas, river profile

2. Survey Content and Methods

The 2nd,3rd and 5th surveys covered the main channels of 109 first-class rivers throughout Japan plus 3 major first-class river tributaries and the Urauchi River in Okinawa Prefecture (113 rivers, total).

The 4th survey selected 153 rivers from among major second-class river main channels and first-class river tributary, such as rivers with large watersheds, rivers that support a rich variety of plants and animals or rivers that flow through sound natural areas.

The survey looked at river alterations and freshwater fish fauna. Further, the 4th and 5th survey did a general survey of river characteristics covered river length, flow volume, changes in water levels, and life-forms in and along the rivers.

- River Alterations
Documentary surveys and confirmative field surveys were conducted with respect to 7 items, including the alteration status of water lines (which involves determining the ratio of embankments installed along water lines) and the status of riverside land usage (which involves classifying the riverside land into "natural land", "farmland", "unused reclaimed land" and "land for facility purposes").

- Freshwater Fish Fauna
By sampling and documentary research, the 2nd and 3rd surveys recorded fish species names, the amount of catches, water discharge and three other items along 107 rivers(excluding Yubetsu River, Abashiri River, Ishikari River, Shiribetsu River, Mukawa River, and Kushiro River in Hokkaido). The 4th survey looked at 153 rivers.

From the 2nd to the 5th surveys, wilderness watershed survey was carried out throughout the country using documentary records and aerial photography.

- Wilderness Watershed Survey
The survey extracted wilderness watershed areas, which cover an area of more than 1,000ha without man-made objects or logging and looked into changes over time.

- Survey of River Profile
In order to identify the profile of rivers targeted in the survey, 14 items were investigated on the basis of various materials, etc., including flow volume, water quality and biota profile (which involved writing down several high-priority species with respect to each organism group* (*: by attached algae, submerged plant, fish or other organism group).

3. Survey Results

(1) Summary of Results of the 3rd Basic survey

1) River Alterations
The overall length of the target rivers was 11,412 km.

Artificial riverfront occupied 2,441.5km; 21.4% of the target population. The extent of artificial riverfront increased by 249.3km (2.2%) since the 2nd survey. There were 3 rivers, Abashiri, Kushiro and Uranai rivers, with no cross-river constructions (dams, weirs, etc.). There were 13 rivers where fish could move to upper stream, including the 3 above-mentioned plus others which had cross-river constructions with fishway.

**Riverfront Alterations: distance (km), ( ): %**
Survey Year	No. of Rivers	Total	Natural Riverfront	Artificial Riverfront
2nd Survey (1979)	113	11,425.0 (100.0)	9,232.8 (80.8)	2,192.2 (19.2)
3rd Survey (1985)	113	11,412.0 (100.0)	8,970.5 (78.6)	2,441.5 (21.4)
5th Survey (1998)	113	11,387.5 (130.7)	8,710.1 (100.0)	2677.4 (30.7)

(Note 1) There were 113 rivers in the 2nd and 3rd surveys - main channels of first-class rivers and major first-class river tributaries plus Urauchi River in Okinawa.

2) Freshwater Fish Fauna
Rivers with a high fish species count were almost all major rivers in Honshu. The leaders were the Shinano and Chikugo rivers with 63 species each. Rivers with a low species count were either in Hokkaido (for example, the Rumoi River) or fast-flowing rivers (Kurobe River and others) or short rivers (Tenjin River, etc.).

3) Wilderness Watershed
There were 100 wilderness watersheds with total area of 211,879ha.
Since 2nd survey, 11 areas comprising 17,386ha no longer met criteria because of modifications to the environment. 79 areas were in protected areas. Since the 2nd survey, 23 areas were designated as a part of protected areas including 19 areas of the Hidaka-Sanyaku-Erimo Quasi-National Park.

(2) Summary of Results of the 4th Basic survey

1) River Alterations
Main channel length of the major second-class and first-class river tributaries included in this survey was 6,249.0km. Within this total, 1,663.4km, or 26,6% of the total contained artificial riverfront, leaving 4,585.6km or 73.4% in the natural state. There were 91 rivers (59% of survey rivers) with 30% or less of artificial riverfront.

There were 1,680.3km of riverside in the survey, 26.9% of the total river length. 1,379.3km of this (82.1%) were natural; 301.0km(17.9%) were modified. Artificially-modified land was prominent along riversides of Hokkaido-Okhotsk Sea river systems, and Hokkaido-Sea of Japan river systems.

**Riverfront Alterations distance (km) ( ): %**
Survey Year	No. of Rivers	Total	Natural Riverfront	Artificial Riverfront
4th Survey (1992)	153	6,249.0 (100.0)	4,586.6 (73.4)	1,663.4 (26.6)

(Note 2) The 4th survey selected from among major second-class river main channels and first-class river tributaries those flowing through sound natural environments, or with large watersheds, or supporting rich variety of plants and animals - a total of 153 rivers.
(Note 3) The 4th survey cannot be compared with 2nd, 3rd or 5th surveys due to different survey targets.

2) Freshwater Fish Fauna
There were 18 rivers reporting the existence of more than 40 fish species. The Arita River (83 species), the Ibi River (65 species) and the Shinsho River (63 species) had the greatest variety. River systems with a great variety of fishes tended to be long rivers, second-class river main channels, and rivers flowing into the Pacific Coastal line in the central and southern parts of Honshu and into the Seto Inland Sea in Honshu and in western Japan.

3) Wilderness Watershed
There were 99 watersheds nationwide with a total area of 205,634ha, a reduction of 2 since the 3rd survey, and a total shrinkage of area of 5,936ha. Factors in the shrinkage included logging or selective logging in 6 of the 13 areas and road construction in 5 areas. 79 of the 99 watersheds were covered with some kind of protected area; the remaining 20 had no protection designation.

(3) Summary of Results of 5th Survey

1) River Alterations
The total length of rivers targeted in the survey (main channels of first-class rivers, etc.) was 11,388km, of which artificially-structured water lines occupied 2,677.4km (23.5%) and natural land occupied 8,701.1km (76.5%). Artificial water lines increased 235.9km (2.1%) nationwide since the 3rd survey.

There were two rivers with no cross-river constructions in the survey zones, namely, Rumoi River and Urauchi River. There were twelve rivers nationwide with constructions but with no cross-river constructions that prevented fish from swimming upstream due to the proper functioning of fishways, including the two aforementioned rivers.

2) Wilderness Watershed Survey
There were 102 wilderness watershed areas nationwide, totaling 201,037ha. Since the 4th survey, no wilderness watershed areas have been de-listed due to alterations. Three new watershed areas were recognized, namely, the upper reaches of Esaomantottabetsu River in Hokkaido (1,607ha), the upper reaches of Kumanosawa Stream in Hokkaido (1,895ha) and Sodekawazawa Stream in Akita Prefecture (1,365ha). However, the total area decreased by 2,482ha since the 4th survey. This is because watershed areas meeting the wilderness watershed criteria suffered a decrease in catchment area (9 areas, totaling 7,999ha), more than offsetting the newly-recognized wilderness watershed areas.

Of all wilderness watershed areas, those in designated conservation zones totaled 82, while those completely outside the designated conservation zones totaled 20.