Total Maximum Daily Loads

NRCS scientist and farmer working with nutrient management software.

This page contains introductory information regarding total maximum daily loads (TMDLs). A TMDL serves as a planning tool and potential starting point for restoration or protection activities with the ultimate goal of attaining or maintaining water quality standards

Total Maximum Daily Load Research
USDA. National Agricultural Library.
Searches for TMDL-related citations in AGRICOLA, NAL's catalog of books and articles. Some full text materials are available.


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Implementation: What Happens after the TMDL (Total Maximum Daily Load) is Developed?
Virginia Cooperative Extension.
To translate reductions specified in the TMDL into changes in the watershed, a TMDL Implementation Plan (IP) is developed. This is the next step in the process of restoring water quality.

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Assessing the TMDL Approach to Water Quality Management
National Academies Press.
Report focuses on how scientific data and information should be used within the TMDL program.

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Evaluating Options for Documenting Incremental Improvement of Impaired Waters under the TMDL Program
Environmental Protection Agency.
Offers working examples of detecting and quantifying incremental improvement of impaired waters and summarizes key TMDL concepts and methods in a consistent framework.

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Unleashing the Clean Water Act: The Promise and Challenge of the TMDL Approach to Water Quality
Resources for the Future
Provides a brief but thorough introduction to the implementation of TMDL rules.

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Protocol for Developing Pathogen TMDLs
Environmental Protection Agency.
A guidance document for the development of total maximum daily loads.

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Protocol for Developing Nutrient TMDLs
Environmental Protection Agency.
A guidance document for the development of total maximum daily loads.

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Developing Total Maximum Daily Load Projects in Texas: A Guide for Lead Organizations
Texas Natural Resource Conservation Commission; Texas Institute for Applied Environmental Research; Texas A&M University System.
Serves as a how-to guide for use in developing TMDL projects.

Water Quality Assessment and TMDL Information
“This site provides information reported by the states to EPA about the conditions in their surface waters. This information is required every two years under Clean Water Act Sections 305(b) and 303(d).

Impaired Waters and Total Maximum Daily Loads Program
Environmental Protection Agency.
Includes access to the documents, Approach for Using Load Duration Curves in the Development of TMDLs (PDF | 3.3MB) and Twenty Needs Report: How Research Can Improve the TMDL Program (PDF | 1.1MB). Also provides links to EPA Regional TMDL Web sites.


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Total Maximum Daily Load (TMDL) Program
New Hampshire Department of Environmental Services.
"The term 'total maximum daily load' (TMDL) refers to the calculation of the maximum amount of a pollutant that a waterbody can receive, and attain or maintain water quality standards for its designated use. The TMDL calculation allows for the determination of a carefully identified allowable pollutant load equivalent to the sum of the waste load allocations (WLA) for point sources, load allocations (LA) for nonpoint sources and naturally occurring background sources, and an allocation of that load among the pollutant's sources. The TMDL calculation is required to account for seasonal variations and it must include a margin of safety (MOS) that accounts for uncertainty and any lack of knowledge concerning the relationship between effluent limitations and water quality."

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Overview of Impaired Waters and Total Maximum Daily Loads Program
Environmental Protection Agency.
Describes the water-quality based approach to protecting and restoring the nation's waters. The TMDL program is designed to achieve the desired uses of a water and may ultimately result in more stringent ...permit limits. 

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Total Maximum Daily Load (TMDL) Program
California State Water Resources Control Board.
Describes and lists TMDL efforts statewide in California.

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Total Maximum Daily Loads (303d) Guidance
Illinois Environmental Protection Agency.
Find regular updates from EPA containing guidance for program management, reporting, listing (of impaired waters), and development of the water quality tools. The Total Maximum Daily Load (TMDL) program is under Section 303d in the Clean Water Act (Public Law 92-500).

303(d) Listing and TMDL Information Expert Query
Environmental Protection Agency.
Search National Total Maximum Daily Load (TMDL) Tracking System (NTTS) and TMDL information. AskWATERS can generate cross-program calculations, examines spatial relationships between programs, performs nationwide analyses, produces multi-program inventory reports for a given geographic area, and investigates interstate water quality issues.

TMDL Final Rule
Environmental Protection Agency.
Provides the text of the Jul 13, 2000 Federal Register notice that contains the total maximum daily load final rule. See also the final rule fact sheet (PDF | 25 KB).


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Clean Water Act
National Agricultural Law Center.
The Clean Water Act "provides a comprehensive system for the regulation of pollutants in the waters of the United States with the objective of restoring and maintaining the chemical, physical, and biological integrity of the nation’s waters." See two related CRS reports, Water Quality: Implementing the Clean Water Act (updated 2006, PDF 147KB) and Clean Water Act: A Summary of the Law (2010; PDF 170KB).