| The Lake Biwa-Yodo River basin, covering 8,240 km² with a channel length extending 75.1 km, is a representative basin of Japan and encompasses six prefectures, including Mie, Shiga, Kyoto, Osaka, Hyogo, and Nara. Approximately 12 million people live in the basin, and Lake Biwa is a source drinking water for over 14.5 million people in the Kansai region.
Until the latter half of the 20th century, rapid changes in society had deteriorated the water quality of the basin. An increase in sewerage plants, coverage area, and effluent regulations had contributed to reduce causes of water pollution and improved the water quality. However, over the past 20 years, changes in water quality have occurred due to changes in social structure, such as population growth and varieties of land use, as well as global climate change.
To aid other studies, the Institute of Lake Biwa-Yodo River Water Environmental Research has prepared maps, which integrated local data including water quality and related data. These maps are available as available as analysis tools to consider water quality improvement, measures for future water conservation, and water environment management. These tools help to see conditions of the entire basin form a bird’s eye view.