Kumamoto City

Kumamoto, a World Renowned City ofGroundwater Conservation:
Collaborative Efforts in Groundwater
Conservation beyond Municipal
Boundaries
Background and Reason for the Project

Project Aims

Kumamoto City has been blessed with pure

To conserve groundwater, which covers 100% of thegroundwater since ancient times, and has utilised it

water supply for the city's 740,000 residents, infor

terms of both quality and quantity.

variouspurposes.

However,

withtheimprovement of living standards and economic

To collaborate with 11 municipalities (belowdevelopment, there have been issues with anreferred to as the Kumamoto region) that share

increase in demand for groundwater and a decrease

groundwater and work together on a wide-ranging

in the amount of spring water.

groundwater conservation effort.

Therefore, for two years from 1973 to 1974,

To position water as a strategic resource for

Kumamoto Prefecture and Kumamoto City jointly

enhancing the appeal of Kumamoto City andconducted a ‘Kumamoto City and Surrounding Areas

establish it as part of the city’s brand.

Groundwater Survey’, which came to the conclusionthat the amount of groundwater runoff exceeded

Project Outlinethat of groundwater recharge.

1. Preservation of Groundwater Quality

Furthermore, due to plans for constructing

Operation of the ‘Eastern Composting Centre’,apartments near the water source area, nearby

with the goal of preventing groundwater pollution

residents expressed concerns about the impact on

caused by nitrate nitrogen.

the water source and started an opposition

2. Preservation of Groundwater Quantity

movement. In response, Kumamoto City conducted

Implementation of projects such as flooding ricefurther investigations.

paddies in the middle basin of the Shirakawa River

As a result of these issues, public interest inand encouraging citizens to save water.

groundwater gradually increased, leading to the3. Preservation of Groundwater through Wide-resolution of the ‘Declaration of Groundwater

ranging Collaboration and Cooperation

Conservation City’ by the Kumamoto City Council inEngagement

1976, aiming to ‘permanently preserve the limited

conservation

groundwater and pass it down to future generations.’

contributions to the ‘Kumamoto Groundwater

Since then, the city has been working onFoundation’, a public interest corporation.

groundwater conservation for over 40 years.
1inwide-ranging
effortsthroughgroundwater
financial4. Promotion of the Kumamoto Water Brandregion. Kumamoto City collaborates with Ōzu,Creation and promotion of the city’s brandKikuyō, and local land improvement districts tofeaturing a unique water culture and local

conduct the rice paddy submergence project,characteristics.

artificially flooding of rice paddies in this area.

5. Utilisation of Groundwater in Disaster Response

Kumamoto City, downstream from this area,

Preparation for disasters by signing agreements

provides subsidies to farmers who cooperate inwith local companies for the establishment ofthis project.

emergency wells.

Special Features and Innovations
1. Preservation of Groundwater Quality
In April 2019, as the first composting facility inJapan aimed at preventing groundwater pollution,
Kumamotocityestablishedthe‘Eastern

Composting Centre’ to reduce nitrate nitrogen.
This facility ferments livestock excrements toproduce high-quality compost, which is then usedby surrounding farms to prevent an increase innitrate nitrogen concentration. Additionally, aFlooding of rice paddies in the middle basin of themechanism of circulation through wide-area

Shirakawa River in Kumamoto City.

distribution is established by selling some of the(2) Water Conservation Campaign

compost at home centres and other outlets.

Since

2005,

efforts

have

been

madeincollaboration with citizens and businesses toreduce domestic water usage, which accounts for
80% of total water consumption. These efforts
include organizing parades to promote water
conservation

andconducting

awareness

campaigns through various media channels.
(3) Supporting Rainwater Penetration
In urbanized areas, measures are taken to increase
rainwater

The process of compost production at the East Composting

infiltration.

The‘KumamotoCity

Groundwater Conservation Ordinance’ mandates

Centre in Kumamoto City.

2. Preservation of Groundwater Quantity

the installation of rainwater penetration facilities(1) Project of flooding rice paddies in the middle

during development and construction projects.

basin of the Shirakawa River

Guidance is provided during pre-construction

The rice paddies in the Shirakawa middle basin,

surveys and other administrative procedures.

which extends across Kumamoto City's eastern

Additionally, Kumamoto City offers its own subsidy

area and neighbouring towns Ōzu and Kikuyō,

program forhave a unique geological structure that allowspenetration pits.

the installation

ofrainwater

water to penetrate 5 to 10 times more easily

3. Conservation of Groundwater through Wide-compared to typical rice paddies. This area isrange Collaboration and Cooperation

crucial for groundwater recharge in the Kumamoto

In order to address groundwater conservation2

across municipal boundaries and to engage

Taking lessons from the Kumamoto earthquake,residents, businesses, and administrations in a

Kumamoto City has prepared measures to swiftly

unified effort, the 11 municipalities in thesecure water in the event of a disaster. The city has

Kumamoto region established the ‘Kumamoto

signed agreements with 95 companies and other

Groundwater Foundation’, a public interest

entities that own wells (96 wells) in the city forcorporation, in 2012. This foundation conducts‘emergency wells’ as of the end of October 2023.

fourincluding

In the event of a water outage across the city due

surveys,

to a natural disaster, these companies will provide

publicinterest

groundwaterprojects,

environmental

complementing the efforts of the prefectural andwell water free of charge.

municipal governments to conserve groundwater.
Kumamoto City contributes financially to thisResults of the Projectfoundation.

Local groundwater pollution that has been identified

4. Promotion of the Kumamoto Water Brand

so far is being addressed with purification measures(1) Kumamoto Water Guardians (Mizumori)and continued monitoring based on concentration

The city has registered the nickname ‘Mizumori’ tolevels. Consequently, improvements have beenpromote the protection of water and water culture,observed in the extent and concentration of theas well as the fascination of water. This initiativepollution. The impact of the Eastern Compostinginvolves training individuals and providing related

Centre after its establishment and operation willinformation.

become more and more apparent, so proper(2) Kumamoto Water Heritage

operation will continue in the future.

Resources related to the nature, history, customs,

Thegroundwaterlevel,

whichhad

beenand personalities associated with water indecreasing for many years, has been showing a trend

Kumamoto City are publicly solicited, registered,of recovery in recent years, and the water usage byand honoured as Kumamoto heritage.

citizens is gradually decreasing.

Issues, Problems and Responses
In the eastern region where the trend of increasing
nitrate nitrogen concentration in groundwatercontinues, it is necessary to continue the operationof the Eastern Composting Centre and implement
further wide ranging measures in the upstream area.
Since it takes a long time for polluted groundwater torecover, it is crucial to prevent groundwater pollutionin advance.
Regarding groundwater quantity, the rice paddy

Lake Ezu, registered as part of the Kumamoto Water
Heritage.

inundation project is facing issues such as the(3) Kumamoto ‘Water’ Certification
The‘KumamotoWaterCertification’decrease in agricultural land, changes in farming
wasmethods, and a shortage of successors. However, in

introduced in 2008, which allows people to enjoy

order to enlarge the groundwater recharge amount,and learn about water in Kumamoto.

it is necessary to work with relevant organizations to

5. Utilisation of Groundwater for Disaster

implement measures such as extending thePrevention

inundation period, expanding the area, and3

reviewing the used crops, as well as expanding thesystem.
To address these challenges, we will continue topromote the five projects mentioned above.
Future Developments (expected effects and projectvision and issues)
These wide-range groundwater conservation efforts
involving residents, businesses, and administrations
have been recognized worldwide, and our city hasreceived the ‘2013 UN Water for Life Best Practices
Award’. In April 2022, under the participation ofleaders and ministers from 30 countries in the AsiaPacific region, including Japan, the ‘4th Asia-PacificWater Summit’ was held, and the ‘Kumamoto
Declaration’, an outcome of the summit, waspresented to the world at the March 2023 ‘UN WaterConference.’
We will continue the city's recognized efforts ingroundwater conservation and aim to contribute tosolving global water issues by continuing to work
closely with various stakeholders and taking aleading role in addressing water-related challenges.

Reference URL
Kumamoto Water Life
(https://www.city.kumamoto.jp/kankyo/hpkiji/pub/
List.aspx?c_id=5&class_set_id=20&class_id=2655)

Contact:
Division in Charge: Water Conservation Division
Tel.: ＋81-96-328-2436
E-mail: mizuhozen@city.kumamoto.lg.jp

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