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Natural Resources Extension Program
TMDL - Total Maximum Daily Load - Water Quality
Modified from Living on the Land
2001: Stewardship for Small Acreages Project Leader:
Susan Donaldson, University of Nevada, Cooperative Extension
| "...a
calculation of the maximum amount of a pollutant
that a water body can receive and still meet water
quality standards." |
A TMDL or Total Maximum Daily Load is a calculation
of the maximum amount of a pollutant that a water body
can receive and still meet water quality standards.
The Clean Water Act, section 303, establishes the TMDL
program.
Water quality standards are set by states, territories,
and tribes. They identify the uses for each water body,
for example, drinking water supply, contact recreation
(swimming), and aquatic life support (fishing), and
the scientific criteria to support those uses. The standards
cannot be set below EPA standards – they can be
more restrictive, but not less.
 A
TMDL is the sum of the allowable loads of a single pollutant
from all contributing point and nonpoint sources plus
a margin of safety. The calculation must include a margin
of safety to ensure that the water body can be used
for the purposes the State has designated. The calculation
must also account for seasonal variation in water quality.
Useful link:
EPA's TMDL Program: http://www.epa.gov/owow/tmdl/atlas/index.html
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