Groundwater Conservation in Kumamoto City - 1999 to 2020s

Groundwater Conservation in Kumamoto City - 1999 to 2020s

Kumamoto City began its efforts to prevent groundwater depletion by enacting a groundwater conservation ordinance in 1999. This ordinance was very important for the sustainability of the region, as Kumamoto City is one of the few cities in Japan that relies on groundwater for approximately 98% of its drinking water. Since the enactment of the ordinance, regulations and monitoring of groundwater use have been strengthened, requiring appropriate groundwater use in agriculture and industry. At the same time, groundwater levels began to gradually recover as water conservation awareness spread through public awareness campaigns.

Efforts in the 2000s
In the 2000s, a wide-area effort to recharge groundwater was promoted: the Kumamoto Regional Groundwater Conservation Council was established in 2003, and Kumamoto City, surrounding municipalities, and local companies cooperated to formulate a plan for groundwater conservation. This plan includes the recycling use of factory wastewater and the development of rainwater infiltration facilities. For example, in Kikuyo Town, rainwater infiltration facilities were installed to infiltrate rainwater into the ground, resulting in an annual recharge of approximately 300,000 cubic meters. In 2008, a groundwater conservation fund was established to support conservation activities based on donations from companies and citizens.

Initiatives in the 2010s
In the 2010s, addressing climate change became a new challenge for groundwater conservation, and in 2012, Kumamoto City and the Ministry of the Environment jointly developed a "Groundwater Adaptation Strategy" to strengthen the response to reduced precipitation and torrential rainfall. 2015 saw the start of a large-scale reforestation project in Mashiki Town, a major groundwater recharge area in Kumamoto Prefecture, and the start of a reforestation project in the town of Mashiki. A reforestation project was initiated to improve recharge capacity by restoring degraded forests.

In addition, the groundwater monitoring system was further strengthened following the 2016 Kumamoto earthquake. Immediately after the earthquake, rapid changes in groundwater levels were observed in some areas, and it was pointed out that the city's drinking water supply could be affected, but a quick response ensured a stable supply. This experience reaffirmed the importance of groundwater conservation against earthquakes and disasters.

Current Status in the 2020s
In the 2020s, based on the "Kumamoto City Basic Plan for Groundwater Conservation" updated in 2018, a target was set to maintain groundwater levels above the average of the late 1990s; a survey in 2023 confirmed that groundwater levels were 2 meters above the standard value. Cooperation from companies has also been remarkable, with Mitsui Chemicals and other companies in Kumamoto Industrial Park installing equipment to reuse industrial water, thereby contributing to the reduction of groundwater use. In the agricultural sector, water-saving technologies have become widespread and have resulted in the curbing of excessive use in paddy field irrigation. In addition, the Kumamoto Groundwater Future Project has promoted afforestation activities and underground rainwater infiltration in Kikuyo Town and Mashiki Town, resulting in groundwater recharge of 500,000 cubic meters per year.

Kumamoto City's groundwater conservation efforts have become a model case that is attracting attention from Japan and abroad, and is considered a good example of how to harmonize urban development and environmental conservation. On the other hand, addressing new risks such as fluctuations in precipitation due to climate change and the progress of urbanization continues to be a challenge.

Sources
- Kumamoto City official website, "Basic Plan for Groundwater Conservation
- Ministry of the Environment "Kumamoto Groundwater Future Project" report
- Local newspaper articles (1999-2023)
- Materials related to groundwater conservation published by local NPOs