Governing Law and Regulations
Iowa Department of Natural Resources (DNR) Environmental Protection Division Water Quality Bureau
U.S. Environmental Protection Agency (EPA) Region 7
See ADDRESSES & CONTACTS for addresses and telephone numbers.
See national section for basic information and federal regulations.
Comparison: State vs. Federal
• Rules. Iowa has more specific requirements than the federal requirements for regulating water temperatures under its water quality standards and discharge permit programs.
• Administration and enforcement. DNR's Water Quality Bureau administers and enforces the state's water quality program, including thermal discharge requirements.
WATER TEMPERATURE QUALITY STANDARDS
Iowa provides water temperature standards as minimum conditions of water quality and also provides a set of standards based on usage. As a general rule, water temperatures may not exceed 32°C (89.6°F). Heat of an artificial origin cannot be added to the surface water in excess of the amount that would raise the temperature of the water beyond the mixing zone more than 3°C (37.4°F) above natural conditions. Iowa requires that the normal daily and seasonal temperature variations of a surface water existing before the addition of heat must be maintained.
It is the policy of the state of Iowa that existing surface water uses and the level of water quality ...