December 20, 2005
The Ministry of the Environment (MOE) has put together the results of the nationwide water quality survey of public water areas implemented by the national and local governments in FY 2004 pursuant to the Water Pollution Control Law.
Most of the monitoring points have achieved the environmental quality standards (hereinafter referred to as "the EQSs") for the 26 human health items, with the EQS compliance rate reaching 99.3% (Table 1).
In terms of the compliance with the EQSs for BOD and COD, typical indicators of water quality for organic contamination, the overall compliance rate was 85.2%, reaching record-high, with 87.8% for rivers, 50.9% for lakes and reservoirs and 75.5% for sea and coastal areas. In enclosed water areas such as lakes and reservoirs, the compliance rate remains low (Table 2, Figs. 1 & 2).
The EQS compliance rate for total nitrogen and total phosphorus in lakes and reservoirs is 42.9%, remaining at a low level. As for sea and coastal areas, the EQS compliance rates for total nitrogen and total phosphorus have been 78.3 % showing downward trend compared to the previous year. Total lead was added to list of substances for which the EQSs were set, as one of the items relevant to conservation of water life, the survey was conducted in 3,844 survey points across Japan (Fig. 3).
Among rivers and lakes and reservoirs, the reduction ratio of average BOD and COD of Ushizue river and Teganuma lake were highest in FY 2002 to 2004 compared to those in FY 1992 to 1994.