Water data sources in Japan

Real-time risk map and river flood forecasting system with 5-level warning scale

Free | National river systems and urban areas

Real-time water source information including water levels, rainfall, dam operations

Free | 7 major river systems

Japan Ministry of the Environment downloadable database of seawater radioactivity monitoring (tritium and other isotope concentrations, flow rates) associated with the discharge...

Free | Fukushima coastal sea area

Global database of ocean surface microplastic monitoring data, quality-controlled under harmonized guidelines.

Free | Global ocean surface, strongest coverage in Pacific and Atlantic

Water supply performance dashboard visualizing financial and seismic resilience of 1300+ utilities

Free | 1300+ Japanese water utilities

Database collection of the Geological Survey of Japan (AIST), including digital hydrogeological maps, groundwater and subsurface-structure databases accessible online by...

Free | National (Japan)

Official government statistics portal including water resource data

Free | Nationwide

Japan's Geospatial Information Authority provides detailed flood hazard maps, inundation area data, and elevation data critical for flood risk management across Japanese...

Free | National

JMA's Automated Meteorological Data Acquisition System (AMeDAS) provides 10-minute interval precipitation, temperature, and weather data from approximately 1,300 stations across...

Free | National

Marine and coastal water quality data

Free | Japanese waters

Japan's Ministry of Land, Infrastructure, Transport and Tourism hydrological database providing river water level, discharge, dam and radar rainfall observations from ~1,900+...

Free | Japan

Ministry of Land, Infrastructure, Transport and Tourism - national river discharge and dam operation data

Free | Japan nationwide river systems

AIST/Geological Survey of Japan observation-well network (Tokai and Kansai regions) measuring groundwater levels, discharge, radon and crustal strain since 1998, with corrected...

Free | Japan (Tokai/Kansai)

Japan's NIES provides environmental monitoring data including water quality of Japanese lakes and rivers, aquatic ecosystem assessments, and long-term environmental change...

Free | National

40+ year water-quality and aquatic-organism monitoring database for Lake Kasumigaura maintained by Japan's National Institute for Environmental Studies (NIES/CGER), with...

Free | Lake Kasumigaura

JAXA Earth Observation product page for GCOM-W/AMSR2 Level-2/3 Soil Moisture Content (10/25 km), part of the AMSR2 water-cycle suite that also includes precipitation, snow and...

Free | Global

JAXA Satellite Monitoring for Environmental Studies portal providing map-projected global water-cycle observation imagery (soil moisture, snow, precipitation, water vapour) from...

Free | Global

1km resolution ocean weather forecast service combining JAXA satellite sea surface temperature data with JAMSTEC ocean circulation model. Launched March 2025.

Free | Pacific Ocean (Japanese waters)

APHRODITE high-resolution (0.05-0.25 degree) long-term daily gridded precipitation and temperature for monsoon Asia, Middle East and Russia based on a dense rain-gauge network...

Free | 1951-present, daily

Long-term daily gridded rain-gauge-based precipitation dataset for monsoon Asia, the Middle East and northern Eurasia (0.25 and 0.5 degree), plus high-resolution Japan product.

Free | Asia, Middle East, Eurasia

Japan's national earth-science data platform (MEXT/JAMSTEC) archiving and serving large hydrological, climate and water-cycle datasets, including MLIT XRAIN radar rainfall and the...

Registration Required | National and Global

Volunteer-based global monitoring of persistent organic pollutants accumulated on beached plastic resin pellets from 300+ locations in 40+ countries, analyzed via chemical...

Free | 50+ countries, 300+ coastal locations