Classification of rivers in Japan

Rivers in Japan are classified according to criteria set by the River Law (河川法, Kasen Hō), which was introduced in 1967.^[1]^[2] Rivers are designated as Class A or Class B river systems by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT).

Class A rivers

Class A river system (一級水系, Ikkyū suikei) is a designation applied to rivers and waterways deemed to be important to the economy of the nation as a whole, as well as those deemed important to the conservation of nature within Japan. There are currently 109 rivers with this designation.^[3]

List of Class A river systems

The number of dams only includes existing and unestablished dams that meet the criteria (15 metres (49 ft) or more in bank height) of the River Law. The management entity is irrelevant. The number in parentheses is the number of dams on the main river, excluding tributaries. The number of dams does not always exceed the number of hydroelectric plants because plants with intake weirs less than 15 metres (49 ft) high are not considered dams.

The acronym BOD refers to biochemical oxygen demand.

Hokkaidō Development Bureau

Name	Main stream length (km)	Basin area (km²)	Basin management	Basin area population	Tributaries	Average annual flow rate (m³/s)	BOD (ppm)	Dams	Hydroelectric plants
Teshio	256	5,590	Hokkaidō	94,000	160	134.52	0.7	14 (2)	3
Shokotsu	84	1,240		28,000	25	29.33	1.0	0	2
Yūbetsu	87	1,480		36,000	17	32.45	1.7	1 (0)	3
Tokoro	120	1,930		142,000	57	22.64	2.6	2 (1)	0
Abashiri	115	1,380		94,000	25	14.02	2.5	1 (0)	2
Rumoi	44	270		28,000	13	11.84	1.5	3 (0)	0
Ishikari	268	14,330		2,500,000	464	133.18	1.1	83 (1)	34
Shiribetsu	126	1,640		38,000	40	68.41	0.4	3 (0)	7
Shiribeshi-Toshibetsu	80	720		16,000	29	23.69	0.5	2 (1)	8
Mu	135	1,270		13,000	20	38.54	0.6	2 (0)	1
Saru	104	1,350		13,000	28	48.24	0.6	4 (2)	4
Kushiro	154	2,510		177,000	38	26.32	1.7	0	0
Tokachi	156	9,010		340,000	209	85.36	1.7	14 (3)	16

Tōhoku Development Bureau

Name	Main stream length (km)	Basin area (km²)	Basin management	Basin area population	Tributaries	Average annual flow rate (m³/s)	BOD (ppm)	Dams	Hydroelectric plants
Iwaki	102	2,540	Aomori	482,400	97	76.07	1.6	21 (2)	5
Takase	64	867	Aomori	80,372	23	50.10	0.9	3 (1)	0
Mabechi	142	2,050	Iwate, Aomori	188,000	30	47.62	1.1	6 (0)	5
Kitakami	249	10,150	Iwate, Miyagi	1,389,000	302	318.42	1.1	53 (1)	33
Naruse	89	1,130	Miyagi	190,000	61	26.49	1.3	13 (1)	3
Natori	55	939	Miyagi	1,125,589	30	17.32	1.1	9 (0)	7
Abukuma	239	5,400	Miyagi, Fukushima	1,380,000	197	52.22	1.9	19 (2)	25
Yoneshiro	136	4,100	Akita, Iwate	280,000	89	100.91	1.3	21 (0)	22
Omono	133	4,710	Akita	346,481	168	259.02	1.4	34 (0)	17
Koyoshi	61	1,190	Akita	80,000	44	60.60	1.1	12 (1)	7
Mogami	229	7,040	Yamagata	999,300	429	369.26	1.0	41 (1)	26
Aka	70	857	Yamagata	109,294	44	65.68	1.0	5 (1)	10

Kantō Development Bureau

Name	Main stream length (km)	Basin area (km²)	Basin management	Basin area population	Tributaries	Average annual flow rate (m³/s)	BOD (ppm)	Dams	Hydroelectric plants
Kuji	124	1,490	Fukushima, Ibaraki	201,981	53	23.58	0.8	1 (0)	7
Naka	150	3,270	Tochigi, Ibaraki	912,217	197	74.43	0.9	22 (2)	12
Tone	322	16,840	Gunma, Nagano, Tochigi, Saitama, Tokyo, Chiba, Ibaraki	12,140,000	819	237.10	2.5	70 (4)	98
Ara	173	2,940	Saitama, Tokyo	9,300,000	127	27.77	4.4	13 (2)	11
Tama	138	1,240	Yamanashi, Tokyo, Kanagawa	4,250,000	52	40.28	1.7	2 (2)	5
Tsurumi	43	235	Tokyo, Kanagawa	1,840,000	11	7.83	8.0	0	0
Sagami	113	1,680	Yamanashi, Kanagawa	1,200,000	104	－	2.0	10 (3)	20
Fuji	128	3,990	Nagano, Yamanashi, Shizuoka	1,600,000	555	58.91	2.3	19 (0)	71

Hokuriku Development Bureau

Name	Main stream length (km)	Basin area (km²)	Basin management	Basin area population	Tributaries	Average annual flow rate (m³/s)	BOD (ppm)	Dams	Hydroelectric plants
Ara	73	1,150	Yamagata, Niigata	40,000	61	115.00	0.6	5 (3)	6
Agano	210	7,710	Fukushima, Gunma, Niigata	590,000	243	401.55	0.6	62 (8)	60
Shinano	367	11,900	Nagano, Gunma, Niigata	2,950,000	880	503.15	1.0	90 (1)	122
Seki	64	1,140	Nagano, Niigata	210,000	78	50.32	1.5	5 (1)	16
Hime	60	722	Nagano, Niigata	20,000	47	44.07	0.5	0	19
Kurobe	85	682	Toyama	71,000	25	37.00	0.8	6 (5)	18
Jōganji	56	368	Toyama	30,000	49	16.23	0.6	8 (1)	27
Jintsū	120	2,720	Gifu, Toyama	380,000	105	183.65	1.4	25 (7)	60
Shō	115	1,180	Gifu, Toyama	28,032	48	47.72	1.0	18 (9)	27
Oyabe	68	667	Ishikawa, Toyama	300,000	64	27.99	1.5	14 (2)	5
Tedori	72	809	Ishikawa	40,000	35	77.21	0.5	7 (2)	24
Kakehashi	42	271	Ishikawa	110,000	13	18.02	1.0	1 (1)	0

Chūbu Development Bureau

Name	Main stream length (km)	Basin area (km²)	Basin management	Basin area population	Tributaries	Average annual flow rate (m³/s)	BOD (ppm)	Dams	Hydroelectric plants
Kano	46	852	Shizuoka	640,000	76	21.40	1.5	0	7
Abe	51	567		170,000	36	41.44	0.8	0	2
Ōi	168	1,280		90,000	39	76.40	0.5	14 (7)	15
Kiku	28	158		70,000	25	2.21	1.8	2 (0)	0
Tenryū	213	5,090	Nagano, Aichi, Shizuoka	720,000	332	239.67	0.5	17 (5)	51
Toyo	77	724	Aichi	210,000	27	28.23	0.6	9 (1)	3
Yahagi	118	1,830	Nagano, Gifu, Aichi	690,000	94	43.99	1.0	25 (3)	25
Shōnai	96	1,010	Gifu, Aichi	2,500,000	76	26.21	4.7	18 (0)	2
Kiso	229	9,100	Nagano, Gifu, Shiga, Aichi, Mie	1,700,000	391	291.05	0.7	64 (9)	77
Suzuka	38	323	Mie	110,000	46	11.23	1.4	0	0
Kumozu	55	550		90,000	40	14.36	1.6	6 (0)	1
Kushida	85	461		40,000	68	20.55	0.7	4 (0)	5
Miya	91	920		140,000	55	45.70	0.5	5 (2)	6

Kinki Development Bureau

Name	Main stream length (km)	Basin area (km²)	Basin management	Basin area population	Tributaries	Average annual flow rate (m³/s)	BOD (ppm)	Dams	Hydroelectric plants
Kuzuryū	116	2,930	Gifu, Fukui	666,225	147	108.26	0.8	20 (3)	25
Kita	30	211	Shiga, Fukui	21,389	12	11.68	0.6	1 (0)	1
Yura	146	1,880	Hyōgo, Kyōto	300,000	138	52.09	0.8	22 (3)	6
Yodo	75	8,240	Shiga, Kyōto, Ōsaka, Mie, Nara, Hyōgo	11,650,000	965	267.51	1.9	66 (1)	34
Yamato	68	1,070	Nara, Ōsaka	2,150,000	178	23.94	3.3	11 (1)	0
Maruyama	68	1,300	Hyōgo	150,557	97	37.40	0.9	7 (0)	5
Kako	96	1,730		820,000	130	45.89	2.6	19 (0)	0
Ibo	70	810		200,000	47	29.04	0.8	4 (0)	6
Kino	136	1,750	Nara, Wakayama	689,000	181	58.77	2.1	9 (2)	6
Kumano	183	2,360	Nara, Mie, Wakayama	84,000	103	163.54	1.3	11 (5)	30

Chūgoku Development Bureau

Name	Main stream length (km)	Basin area (km²)	Basin management	Basin area population	Tributaries	Average annual flow rate (m³/s)	BOD (ppm)	Dams	Hydroelectric plants
Sendai	52	1,190	Tottori	200,000	87	61.68	0.8	6 (0)	17
Tenjin	32	490		65,500	32	24.03	1.2	8 (0)	8
Hino	77	870		60,800	56	33.55	1.1	12 (0)	14
Hii	153	2,070	Shimane, Tottori	435,000	227	40.26	1.4	24 (2)	13
Gōno	194	3,900	Hiroshima, Shimane	202,000	293	75.17	0.8	20 (2)	24
Takatsu	81	1,090	Shimane	38,600	92	51.88	0.7	4 (0)	5
Yoshii	133	2,110	Okayama	294,000	215	61.16	2.0	30 (1)	18
Asahi	142	1,810	Okayama	335,000	147	57.01	1.8	25 (3)	9
Takahashi	111	2,670	Okayama, Hiroshima	273,000	121	61.81	2.5	29 (1)	19
Ashida	86	860	Okayama, Hiroshima	269,000	82	12.73	4.0	18 (2)	3
Ōta	103	1,710	Hiroshima	980,000	73	78.81	0.9	11 (2)	24
Oze	59	340	Hiroshima, Yamaguchi	26,500	23	12.05	2.6	4 (2)	6
Saba	56	460	Yamaguchi	31,100	32	18.69	0.7	4 (1)	1

Shikoku Development Bureau

Name	Main stream length (km)	Basin area (km²)	Basin management	Basin area population	Tributaries	Average annual flow rate (m³/s)	BOD (ppm)	Dams	Hydroelectric plants
Yoshino	194	3,750	Kōchi, Ehime, Tokushima, Kagawa	641,000	356	107.67	0.8	23 (4)	32
Naka	125	874	Tokushima	59,000	75	62.88	0.7	4 (3)	5
Doki	33	140	Kagawa	35,000	11	1.83	3.9	2 (0)	0
Shigenobu	36	445	Ehime	233,000	75	2.24	5.0	8 (0)	1
Hiji	103	1,210	Ehime	112,000	475	37.61	1.0	8 (2)	4
Monobe	71	508	Kōchi	40,000	35	30.78	0.7	4 (3)	6
Niyodo	124	1,560	Ehime, Kōchi	105,000	166	100.07	0.7	5 (3)	18
Shimanto	196	2,270	Ehime, Kōchi	100,000	319	121.02	0.6	5 (0)	6

Kyūshū Development Bureau

Name	Main stream length (km)	Basin area (km²)	Basin management	Basin area population	Tributaries	Average annual flow rate (m³/s)	BOD (ppm)	Dams	Hydroelectric plants
Yabe	61	647	Fukuoka	182,889	23	21.54	1.1	17 (2)	4
Onga	61	1,026	Fukuoka	666,406	74	31.47	2.6	23 (0)	1
Yamakuni	56	540	Ōita, Fukuoka	36,801	39	20.81	0.9	1 (0)	1
Chikugo	143	2,863	Kumamoto, Ōita, Fukuoka, Saga	1,090,777	235	95.09	1.6	29 (2)	22
Matsūra	47	446	Saga	97,818	80	12.46	2.4	22 (0)	3
Rokkaku	47	341		122,827	79	4.36	2.1	9 (1)	0
Kase	57	368		133,412	51	14.10	1.0	3 (2)	8
Honmei	21	87	Nagasaki	54,583	18	2.11	1.8	2 (1)	0
Kikuchi	71	996	Kumamoto	208,694	68	39.56	1.1	1 (0)	4
Shira	74	480		131,375	16	25.39	2.5	3 (1)	4
Midori	76	1,100		517,189	59	36.17	2.4	4 (2)	11
Kuma	115	1,880		137,375	82	119.92	1.4	11 (4)	20
Ōita	55	650	Ōita	252,808	48	22.33	1.4	7 (1)	14
Banjō	38	464	Ōita	56,527	52	12.17	1.1	5 (0)	0
Ōno	107	1,465	Kumamoto, Miyazaki, Ōita	206,818	138	61.36	0.6	14 (0)	10
Gokase	106	1,820	Kumamoto, Miyazaki, Ōita	127,638	102	60.94	1.1	8 (2)	22
Omaru	75	474	Miyazaki	32,616	16	32.76	0.5	8 (4)	5
Ōyodo	107	2,230	Kagoshima, Miyazaki	601,321	134	107.61	1.3	16 (2)	12
Kawauchi	137	1,600	Kumamoto, Miyazaki, Kagoshima	195,944	129	91.09	0.7	4 (3)	5
Kimotsuki	34	485	Kagoshima	115,578	36	31.69	4.5	2 (0)	3

Class B rivers

The smaller, but important rivers are designated as Class B river systems (二級水系, Nikyū Seikei), nominated and managed by the local governments at the prefecture level, but reported to and concurred by the central government.

References

^ "River Administration in Japan". Ministry of Land, Infrastructure, Transport and Tourism. Retrieved December 31, 2017.
^ "河川法" [River Law] (in Japanese). Ministry of Land, Infrastructure, Transport and Tourism. Archived from the original on June 23, 2016. Retrieved July 6, 2016.
^ "河川法第四条第一項の水系を指定する政令" [River Law Clause 4 Paragraph 1: River System Designation Ordinance] (in Japanese). e-Gov.go.jp. Archived from the original on March 5, 2016. Retrieved July 6, 2016.

This article about the law of Japan is a stub. You can help Wikipedia by expanding it.

[1] "River Administration in Japan". Ministry of Land, Infrastructure, Transport and Tourism. Retrieved December 31, 2017.

[river_law_text-2] "河川法" [River Law] (in Japanese). Ministry of Land, Infrastructure, Transport and Tourism. Archived from the original on June 23, 2016. Retrieved July 6, 2016.

[number_of_rivers-3] "河川法第四条第一項の水系を指定する政令" [River Law Clause 4 Paragraph 1: River System Designation Ordinance] (in Japanese). e-Gov.go.jp. Archived from the original on March 5, 2016. Retrieved July 6, 2016.

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