Organization: Kumamoto Local Government

Kumamoto City is blessed with rich greenery and abundant groundwater. The city, in central Kyushu, the largest southern island of Japan, supplies all of its 730,000 citizens with drinking water from ground sources. Kumamoto’s precious water is the result of collaboration between natural systems and local human activity.

Over thousands of years, pyroclastic flows from Mount Aso have accumulated and become a natural groundwater aquifer. Around 400 years ago, feudal lord Kato Kiyomasa developed paddy fields along the Shira River lowlands. These were easy to permeate and recharge the local groundwater.

Today rapid urbanization, increased population, changing agricultural practices and even consumer lifestyle choices have threatened Kumamoto’s precious resource. The city has made efforts to preserve its “mineral water from the tap” for future generations.

Once known as ‘City of Forest’, since the 1970s Kumamoto’s aquifers have been decreasing. Deforestation has reduced the amount of groundwater percolating, as has increased industrial usage. Paddy fields have been converted to dry fields as citizens eat less rice and more of other crops, thus reducing water recharge. Modern fertilizers, pesticides and livestock waste have increased the necessity for modern purification techniques. What’s more, Kumamoto’s water depends on a groundwater flow system which extends far beyond the city limits. The healthy water system flows through 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 east of Kumamoto City.

Thus major cooperative initiatives began in 2004. The project granted farmers subsidies to flood their converted paddy fields with water from the Shirakawa River after harvesting and before planting their crops. This flooding recharges groundwater levels, but it also limits weeds, insects, diseases, and the problems of continuous agriculture. Flooding also helps reduce the use of chemicals, prevents groundwater pollution and reduces financial costs.

As the forest industry has receded, today broad-leaved trees are planted which improve the recharge capacity of the forests. These species also provide a habitat for a greater range of species, improving biodiversity.

Kumamoto has also established citizen’s awareness initiatives so everyone knows how precious the groundwater is. These range from establishing July to September as ‘Water Saving Months’ to the formation of the Kumamoto Groundwater Foundation, which aims to harmonise water use practices across all sectors.

Keywords: groundwater, participation, water quality, empowering communities, sustainable development.

Location: Japan, Asia and the Pacific

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