Last Updated : 16 November 2022.

日本は、世界でも有数の多雨地帯であるモンスーンアジアの東端に位置し、年平均降水量は1,668 mmで、世界(陸域)の年平均降水量約 1,171 mm の約 1.4 倍となっています。しかし、地形が急峻で河川の流路延長が短く、降雨は梅雨期や台風期に集中するため、水資源賦存量のうち、かなりの部分が水資源として利用されないまま海に流出します。

Legal framework

Conservation of Water Quality in Public Water

The law governing “Environmental Quality Standards for Water Pollutants”

General Measures

The law governing “Factory effluent control, notification of factory establishment, monitoring orders, continuous monitoring, measures for domestic wastewater”

The law governing “Construction of sewerage”

The law governing “Installation of Johkasou , regulation of desludging and production, registration system of johkasou installation worker, licence system of Johkasou desludging technician, etc.”

Special Measures in Enclosed Water Bodies
Lakes and Reservoirs

Special regulations for Planning of plan for the preservation of lake water quality.


Control of total pollutant load, and countermeasures against eutrophication.

Seto Inland Sea
Ariake Sea/ Yatsushiro Sea
Biwa Lake
Potable Water Sources
Groundwater Quality Conservation

Environmental quality standards for groundwater

General Measures

Regulations for toxic substances from factories, purifying orders for polluted groundwater, and continuous monitoring

Sound Water Cycle

Holistic and integrated implementation of policies on water cycle

Other Laws Related to Water Environment

Institutional Arrangement of water