Geography

Japan is an archipelago in East Asia comprising 6,852 islands, with an area of 377,975 Sq.Km. Out of these, four major islands - Hokkaido, Honshu, Kyushu, and Shikoku - form a bow-shaped curve that extends for about 1,900 Km of the total coastline of 3,000 Km. About 70% of these islands are mountainous. Japan is divided into 47 prefectures and into eight regions. The latitude of Japan is 36.2048° N, and the country’s longitude is 138.2529°E.

Population and land use

The population of Japan was 126 Million in mid-2019 as per Population Reference Bureau. Japan has the 11th highest population in the world, making up 1.7% of the total world population. The population density is 341 persons per Sq.Km. The total area of the country is 37.79 Mha, out of which the land area is 36.45 Mha. The area under agriculture is 4.5 Mha and 24.96 Mha is under forest cover.

Climate and rainfall

Most parts of Japan are within the north temperate zone with four seasons a year. The length of the archipelago and the ocean currents along the coasts lend a wide variety of climates to Japan. The major landmasses fall into two typical climatic zones: The Pacific coast climatic zone and the Sea of Japan climatic zone, which have different seasonal distributions of precipitation. The average annual rainfall of 1,700 mm is relatively high in global terms.

Food and agriculture

Japan’s main crop is rice, and it is a leading rice producer. Rice fields make up more than half of national farmlands. Japanese farmers grow a wide variety of other crops, such as wheat, soybeans, tea, vegetables (onions, radish, cucumbers, eggplants, lettuce, tomatoes, etc.) and fruit (apples, oranges, pears, persimmons, etc.). Sugar beet is grown in cold areas and sugar cane in hotter regions. About 73% of Japan is forested or mountainous and is unsuitable for agriculture. The total arable land in Japan is about 4.5 Mha.

Water resources management

Water is a vital resource, particularly for use in rice farming among rural communities, although water use for agriculture is slightly declining, due to the recent decreases in farmlands. The total was 54.4 billion m³ / year, comprising approximately two-thirds of overall water use of 80.9 billion m³ / year in 2011.

Irrigation and drainage

The modern irrigation system in Japan was first introduced in the 1950s when the Aichi Irrigation Project installed one of the fastest advanced automatic-check systems along branch canals to ensure constant and stable water distribution. Japan developed these irrigation canal networks with concrete open channels in both the primary and branch canals. A pipeline system was also introduced in the 1960s for upland crops, while in the 1970s, work began to replace the main canals for paddy fields with pipelines. Pipelines from the 1980s replaced many farm ditches in paddy and upland fields. Farmers draw water individually based on their farming schedules to irrigate their fields as required. Telemonitoring and tele-control systems work well for water management systems. These efforts drastically modernized irrigation in Japan. The total irrigated area in Japan is about 2.9 Mha out of which Sprinkler Irrigation is used on 0.49 Mha and Micro Irrigation is used on 0.06 Mha of land.

River basins

In Japan, there are more than 2800 river basins, of which the government manages 109 rivers. The catchment area of these rivers managed by the government is about 241,000 Km². Out of the total rivers in the country, only ten rivers exceed 200 Km in length. The longest, the Shinano River, winds through the Nagano and Niigata prefectures of Honshu Island and empties into the Sea of Japan. It is 367 Km long and has a specific runoff of 1.389 m³/s/Km². The average surface water resources are about 420 Km³/year. Two hundred forty-seven freshwater aquifers are underlying a total area of 69 130 Km².

Water policies

The Japanese agricultural sector accounts for about 1.0% of the entire country’s GDP. About12% of Japan’s land is suitable for cultivation. Japan has adopted the system of terraced cultivation due to the scarcity of arable land for farming in small areas. Japan manages to get one of the world’s highest levels of crop yields per unit area, with an overall agricultural self-sufficiency rate based of calorie of about 37% from the cultivable lands available.

Legislations

The Land Improvement Act (enacted in 1949) allowed farmers to establish water users’ groups called Land Improvement Districts (LIDs), which are essential for Participatory Irrigation Management (PIM). In Japan, LIDs manage the main irrigation facilities such as dams or headworks. In contrast, farmers or local communities manage terminal canals or small farm roads near paddy fields. Various other countries have adopted the successful PIM model in monsoon climates through international cooperation projects.

ICID and National Committee

Japan joined the ICID in 1951. JNCID secretariat has its office in the Ministry of Agriculture, Forestry, and Fisheries in Japan. Past Vice Presidents were: Mr. T. Seino honorary (1957-1960); Prof. H. Fukuda (1962-1965); Dr. M. Nakahara (1985-1988); Dr. R. Nakamura (1993-1996); Dr. S. Taniyama (2001-2004); and Mr. Shinsuke Ota (2008-2011). Mr. Naoki Hayashida is currently a Vice President of ICID from 2017 to 2020.The Japanese National Committee (JNCID) hosted the 14^th IEC meeting and the 5^th International Congress on Irrigation and Drainage in Tokyo in 1963, and the 7^th Asian Regional Conference in Tokyo in 1989. Dr. Tsugihiro WATANABE is currently the Chairperson of JNCID and can be contacted at jncid@maff.go.jp