We developed a spatial database and tool for calculating properties of a river basin, such as the upstream basin area, land use, rice, and crop planting rate, at any point on the river in Japan using various FOSS4G tools. The data set deployed to the database was derived from Japanese National Land Numerical Information from the Ministry of Land, Infrastructure, Transport and Tourism and various statistics of agriculture from the Ministry of Agriculture, Forestry and Fisheries. The database was constructed with PostgreSQL and PostGIS. The database was converted to SpatiaLite format for using a calculating tool. The calculating tool was developed using QGIS API with Python 3. The tool and database are available via GitHub.
