Water / Soil / Ground Environment

State of Japan's Environment at a Glance: Japanese Lake Environment - Efforts Toward maintaining Water Quality

Efforts Toward maintaining Water Quality

Environmental Quality Standard

According to the Environmental Basic Law, environmental quality standards are established to protect human health and preserve human habitats. The environmental quality standards related to water pollution are items related to human health and items related to the preservation of living environment. The health items include 23 substances that affect human health, such as toxins, biodegradation, and carcinogenic substances. Standards for living environment preservation establish COD standards with the condition that damage has not occurred when water is used as drinking water or for fishing. (Standards may not be enforced for lakes with no water use.) The environment quality standards related to health apply to all water areas. Living environment standards apply to rivers, lakes, and seas. These water bodies are classified according to their utilization status, and the corresponding standards are applied. Environmental administration in Japan is based on the compliance with the required standards.

Comparison of Actual and Target Values for COD of Ten Designated Lakes under the Clean Lakes Law

Actual Value of COD (mg/L)
Target Value of COD
Kamafusa R. 2.9 2.7 (1996)
Kasumigaura L.
(as of Nishiura L.)
8.9 8.1 (1995)
Inba-numa L. 9.3 7.9 (1995)
Tega-numa L. 20.0 16.0 (1995)
Suwa L. 7.0 5.7 (1996)
Nojiri L. 1.8 1.6 (1998)
Biwa L.
(as of Northern Basin)
2.7 2.2 (1995)
Kojima R. 9.4 8.8 (1995)
Nakanoumi L. 5.2 5.5 (1998)
Shinji L. 5.0 4.1 (1998)

Environmental Quality Standards for Lakes
(Natural or Artificial Lakes that hold 10 million cubic meters or more of water)

CategoryWater Quality CriteriaCOD Standard
AA Drinkable after simple treatment such as filtration. 1 mg/L
or less
Akan L., Towada L., Tazawa L., Biwa L.
Suitable for char and river trout habit
A Drinkable after normal treatment such as sedimentation and filtration techniques. 3 mg/L
or less
Hachiro R., Inawashiro L., Oze-numa L., Kasumigaura L., Kawaguchi L., Suwa L., Kurobe Res.
Suitable for salmon and ayu (sweetfish) habit
Swimming is possible
B Usable for Industry after normal treatment such as sedimentation process 5 mg/L
or less
Harutori L., Izu-numa L., Tega-numa L.,
Suitable for carp and crucian carp habit Mikata-goko Ls., Kojima R.
C Usable for Industry after sophisticated treatment such as input 8 mg/L
or less
None in Japan

(Standards other than COD are also applied, i.e., pH, suspended solids (SS), dissolved oxygen (DO), and coliform group.)