World Water Day 2013: Japan groundwater recharge project praised

Highlighted as part of World Water Day, UN-Water awarded a project implemented in the city of Kumamoto in Japan for the conservation of groundwater resources...

Highlighted as part of World Water Day, UN-Water awarded a project implemented in the city of Kumamoto in Japan for the conservation of groundwater resources.

The UN-Water "Water for Life" Best Practices Award said the project helped contribute to the fulfillment of international commitments made on water and water-related issues this year.

Kumamoto City is located in the center of Kyushu, the southern major island of Japan. The city is blessed with rich greenery and abundant groundwater in the volcanic pyroclastic aquifer created by Mt. Aso.

Tap water in Kumamoto City comes from groundwater, which is chlorinated only at a minimum level without further purification. As a result citizens can drink "mineral water from the tap". The city has been undertaking various efforts to maintain their abundant, pure and crystal-clean groundwater.

In cooperation with neighboring municipalities, Kumamoto City government has managed artificial groundwater recharge system using abandoned paddies and protected watershed forests.


Kumamoto city does not have an alternative source for groundwater, and may face a crisis when the groundwater dries up or is polluted. Kumamoto used to be called the 'City of Forest', but with rapid urbanization since the early 1970s the amount of groundwater that percolates has decreased while water use has increased. The decline in groundwater recharge levels from paddy fields, which is due to the practice of converting paddy fields to dry fields, has accelerated the fall in groundwater levels.

One third of Kumamoto region's annual groundwater recharge of about 640 million m3 comes from the recharge of paddy fields. With declining rice consumption and low prices, less land is used for rice production, with a substantial decrease in the recharge through these fields. The use of paddy fields for rice production has dropped to about 50% of the areas that used to be paddy fields. It has also become imperative to take countermeasures against groundwater pollution caused by excessive nitrogen from fertilizers and livestock waste.


Kumamoto City has carried out various initiatives to conserve its groundwater, including the adoption of the Declaration of the Groundwater Preservation City in 1976, and the installation of groundwater observation wells in 1986. As part of these efforts, the city has conducted research on groundwater flow system of the area.

Research revealed that the groundwater recharge depends on the farmland and forests in the upper and middle basins of the Shirakawa River and the Midorikawa River, which run through the towns of Ozu, Kikuyo and Mifune, municipalities located in the east of Kumamoto City.

As a result, the city needs to cooperate with neighboring municipalities in order to conserve groundwater. The city formulated an agreement to maintain and increase the groundwater recharge through cross-municipal cooperation. Major cooperative initiatives started in 2004. It included a project to flood in the converted paddy fields of mid-basin of the Shirakawa River and to maintain the watershed protection forests in the upper basin.

Project to flood in the converted paddy fields

In order to maintain the recharge from paddy fields Kumamoto city started a flooding project through the cooperation with the Council for Sustainable Water Use in Agriculture, which consists of Kumamoto City, Ozu and Kikuyo towns, four local Agricultural land improvement districts, JA (Japan Agricultural Cooperatives) Kikuchi and JA Kumamoto City East Branch, in 2004.

The project provides subsidies to encourage farmers to flood their converted paddy fields with water from the Shirakawa River everyday for one to three months between May and October. Farmers may flood their fields after harvesting and before planting and growing crops.

To ease the fall of rice prices, caused by the decline in rice consumption and surplus of rice, the government of Japan has limited areas and amounts of rice production. Farmers are forced to produce crops other than rice in their paddy fields. These fields are known as "converted paddy fields." Converted paddy fields are not flooded when they are used for cultivation of crops other than rice, and therefore do not contribute to groundwater recharge.

Raising citizens' awareness

Groundwater conservation cannot be achieved only by increasing recharge capacity. Kumamoto City is raising awareness among its citizens to reduce the use of water in the city. With corporate efforts, the groundwater pumping regulations imposed on major groundwater users, and the decline of agriculture, the overall groundwater pumping has steadily decreased since the 1980s year by year. However, due to lifestyle changes, the use of groundwater in everyday life is showing increasing tendencies.

Kumamoto City has carried out various initiatives to emphasize the importance of saving water. At the beginning of the 2008, the city designated three months from July to September as the 'Water Saving Months', disclosing the amount of daily water use per person and promoting the use of water-saving devices.

On April 1st, 2012, local residents, private sectors and the city government went above and beyond their respective positions and came together to form a new organization devoted to the sustainable groundwater management.

With the Kumamoto Groundwater Council as its parent organization, the Kumamoto Groundwater Foundation was incorporated and established. The Kumamoto Groundwater Foundation aims to harmonize the water usage practices of the entire community by improving the maintenance, quality and circulation of the local water supply and recognize groundwater as an important underground natural resources of the area.

UN-Water concluded that the city is taking advantage of the groundwater recharge system to obtain good quality groundwater.


- For more information on the Kumamoto City groundwater management process, please click here.

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