2026 Water Cycle White PaperChapter 3: Maintaining and Improving Storage and Recharge Functions

Chapter 3, “Maintaining and Improving Storage and Recharge Functions,” positions the maintenance and improvement of water storage and recharge functions in forests, rivers, farmland, urban areas, and other settings as essential to maintaining or restoring a sound water cycle. Forests receive precipitation, store it in the soil, recharge groundwater, and purify water. Water-source recharge functions include storing water resources, purifying water, and mitigating floods; forests also contribute to carbon storage and disaster prevention.

The chapter covers, in order, “(1) Forests,” “(2) Rivers and other waterways,” “(3) Farmland,” “(4) Urban areas,” and “(5) Other.” It describes development and conservation measures and other water-cycle policies in each field; the “Other” section covers the adoption of green infrastructure, technical surveys and research, consideration of financing methods, and promotion strategies.

Forests absorb and store carbon dioxide from the atmosphere, and using wood in buildings and other structures also leads to long-term carbon storage. Forests are said to contribute to achieving carbon neutrality, preventing disasters, and maintaining a sound water cycle.

Agriculture and rural areas provide food and also serve roles in land conservation, water-source recharge, biodiversity conservation, landscape formation, and cultural transmission, among others; these benefits are enjoyed by local residents and the public as a whole. Temporary storage of rainwater by paddy fields and upland soils, followed by its gradual runoff, reduces flood occurrence.

Urban surface coverage can reduce rainwater infiltration into the ground, potentially causing springs to dry up, reducing river flows and worsening water quality in ordinary conditions, and increasing river flows during floods. Measures seek to maintain and improve urban storage and recharge functions and reduce flood damage.

Development and conservation were advanced under the Forest and Forestry Basic Plan (approved by Cabinet on June 15, 2021), based on the Forest and Forestry Basic Act (Act No. 161 of 1964), and through the forest planning system under the Forest Act (Act No. 249 of 1951). Measures included replanting after final harvests and thinning, and guiding forests toward diverse, healthy conditions suited to natural conditions through multilayered forests, longer rotations, mixed conifer-broadleaf forests, and broadleaf forests. The circular use of forest resources, including by expanding timber demand, was also promoted, and guidance and advice were provided to local governments and forest owners.

Under the Forest Management Act (Act No. 35 of 2018), a system was promoted to entrust municipalities and other parties with management of forests that were not being properly managed, with the consent of their owners. A May 2025 amendment established a system for aggregation plans, through which local stakeholders share a vision for the future and promote the circular use of forest resources, and introduced measures to reduce municipalities’ administrative burdens. The amendment takes effect in April 2026.

In privately owned forests, measures advanced forest road networks, thinning alongside consolidated operations, and replanting after final harvests. Public entities carried out thinning and other work in remote watershed forests, while the national government did so in national forests. Since fiscal 2012, new forest landowners have been required to notify municipal mayors, and acquisitions of forests by foreign corporations and others have been surveyed since fiscal 2010. Acquisition cases in 2024 totaled 85, covering 382 ha. Measures also included designating protected forests, regulating logging and conversion, installing erosion-control facilities, and operating a land development permit system for privately owned forests. The chapter also describes efforts to promote timber demand and domestic timber supply, train forestry workers, increase the added value of local resources, and make use of forest spaces.

River flood-control projects by river administrators and other parties were advanced alongside basin-wide flood control, which mobilizes an integrated combination of structural and nonstructural measures across the entire basin through stakeholder collaboration. River improvement plans and other policies set out the proper use of rivers and maintenance of normal flow functions, and flows were secured in downstream reaches with reduced water from dams and other facilities. Efforts to maintain river flows included sending reclaimed water from sewage treatment plants to urban rivers where natural flows had declined.

Rivers, sewerage systems, and other infrastructure were developed in response to increased stormwater runoff from urbanization and growth in the population and assets located in flood-risk areas. Basin-wide flood measures combined stormwater storage in detention basins and other facilities with infiltration measures using infiltration pits and permeable pavement. The New Generation Sewerage Support Program promoted storage and infiltration facilities, and flood-control measures using basin storage functions were considered, including the designation of storage-function preservation zones under the Act Partially Amending the Act on Countermeasures against Flood Damage of Specified Urban Rivers and other acts (Act No. 31 of 2021).

In farmland areas, efforts advanced the maintenance and management of stable agricultural water-use systems, farmland development and conservation, and conservation of rural environments and ecosystems; support was also provided for joint activities by local communities. As of 2025, farmland covered approximately 4.24 million ha, or approximately 11% of Japan’s approximately 37.8 million ha of land. Much of the irrigation water used in paddy fields and rainwater infiltrates underground, helping recharge groundwater downstream; the recharged groundwater is reused for domestic and industrial water.

In urban areas, diverse stakeholders conserved and created green spaces and other areas, promoted greening at private and public-interest facilities, and advanced the use of green infrastructure’s storage and recharge functions. Private development and other projects were encouraged to install stormwater storage and infiltration facilities to reduce flood damage and create waterside spaces. An amendment to the Sewerage Act (Act No. 79 of 1958) in 2015 established the flood damage countermeasure area system, and a support system for facility development costs by private entities and others was established in fiscal 2015. A 2021 amendment established a system to certify development plans within designated areas and enabled expanded financial support.

Based on the amended Urban Green Space Conservation Act (Act No. 72 of 1973), the Basic Policy on the Conservation of Green Spaces and Promotion of Greening in Urban Areas (December 2024), also known as the Basic Green Policy, was formulated in December 2024. Efforts under municipal basic green plans and other plans received financial and technical support. In fiscal 2025, the Green Infrastructure Creation Promotion Project supported demonstrations of disaster prevention and mitigation technologies and impact-monitoring technologies, and made the effects of local implementation visible through green-space and forest management and evaluations using satellite imagery and AI.

Through the Green Infrastructure Public-Private Partnership Platform, established in March 2020, efforts advanced the adoption of green infrastructure using shared knowledge and know-how, technical surveys and research, and consideration of financing methods. The Green Infrastructure Technology Catalog (March 2025 edition) and the Green Infrastructure Support Systems Catalog (FY2025 edition) were published, and the Interim Summary of the Guidelines on Finance for Green Infrastructure was published in March 2026.

The Green Infrastructure Promotion Strategy 2023 (September 2023) was comprehensively revised, and the Green Infrastructure Promotion Strategy 2030 (January 2026) was formulated. The strategy is an action plan for the Ministry of Land, Infrastructure, Transport and Tourism’s Environmental Action Plan, formulated in June 2025. It organizes the definition, benefits, and characteristics of green infrastructure and the Ministry’s initiatives, and sets target outcomes through fiscal 2030. Cross-sectoral measures to create an enabling environment include building momentum and understanding, making benefits visible, creating conditions for public and private initiatives, financing, new technologies and digital transformation, and international development. Implementation fields are urban and living spaces, disaster prevention and mitigation, heat stress, biodiversity, regional economies, greenhouse gas reduction, and a circular economy. The strategy aims to make the use of green infrastructure commonplace and achieve a society in harmony with nature by 2050.