1. Introduction

Since 1971, a water quality survey of public water areas, focusing on items that set environmental quality standards (EQSs) for the prevention of water pollution (hereinafter referred to as “EQS items”), has been performed under the provisions of the “Water Pollution Control Law” (enacted in December 1970). This survey, which is based on a monitoring plan established by every prefecture in Japan, has been conducted by local governments (including prefectures and designated cities) under the Water Pollution Control Law and also, in the case of direct-administrative-control areas of Class A rivers, by Regional Bureaus of the MLIT (hereinafter referred to as “Prefectural Governments, etc.”). In addition, since 1995, a water quality survey has also been conducted by Prefectural Governments, etc. in drinking water source areas, monitoring trihalomethane formation potential (THM-FP) under the provisions of the “Law Concerning Special Measures for the Preservation of Water Quality in Headwaters Areas for the Purpose of Preventing Specific Trouble in the Drinking Water Supply” (enacted in March 1994: hereinafter referred to as the “Law Concerning Drinking Water Sources”).
This report was prepared by combining data for EQS items, THM-FP and Monitoring Substances (items to be monitored), all of which were obtained from the results of the FY 2006 water quality survey of public water areas (conducted by Prefectural Governments, etc.).
Since 2000, under the “Law Concerning Special measures against Dioxins” (enacted in November 1999), another water quality survey of public water areas, focusing on dioxin pollution, has also been performed nationwide by prefectures, designated cities and Regional Bureaus of the MLIT. However, these survey results are not included in this report as they are already being collated with other information concerned with air and/or soil issues.

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