State of Japan's Environment at a Glance: Japanese Lake Environment (1996)

Water Quality Bureau
Ministry of the Environment

Japanese Lakes

Japan's major lakes (one hectare or larger) comprise a sizable area of 2,380 square kilometers (0.63% of Japan's land area). Excluding Biwa Lake, large natural lakes in Japan are distributed in the central and northern regions. These "open water bodies" are customarily called lakes, ponds, lagoons, or seas but do not have clearly defined classifications. In addition to these natural lakes, many large-scale artificial lakes were constructed after the Second World War.

	(Remote-sensing imagery was made available by courtesy of the Tokai University Research and Information Center)

CONTENTS

Origin of Lakes

The Importance of Lakes

• Lakes as a Water Source
• Lakes for Fishing
• Lakes as Tourist and Recreation Locations
• Lakes as Conservation Areas for Biodiversity
• Lakes as Natural Balance Preserving Reservoirs

The Central Issue - Eutrophication

Deteriorating Lake Environments

• Changes in Lakeshores
• Invasion of Exotic Species

Efforts Toward Maintaining Water Quality

• Environmental Quality Standard
• Water Pollution Control Law
• Law Concerning Special Measures for Conservation of Lake Water Quality (Clean Lakes Law)
• Measures for Other Lakes

A Solution with Multiple Measures

Basin Management Measures

• Sewage System Installation
• Small-scale Wastewater Facilities for Rural Communities (Rural Sewage Systems)
• Integrated Septic Tank Treatment System for Domestic Wastewater
• Measures for Wastewater Discharged from Factories or Other Facilities
• Measures for Agriculture, Livestock, and Fishing

In-Lake Cleaning Measures

• Diversion
• Water Conveyance (Dilution)
• River Water Improvement
• Promotion of Aeration and Water Circulation
• Managing Water Weeds, Water Bloom, and Algal Bloom
• Dredging
• Ecosystem Conservation

Community Responsibility for Lake Clean-up

• Taking Care of Household Wastewater
• Cooperation in Upper and Lower Reaches
• Educating the Next Generation
• Citizen Participation
• Lake Research
• International Cooperation