TMDLs and Ohio agriculture


By Greg LaBarge, CCA, Ohio State University Extension; Rick Wilson, Ohio EPA Division of Surface Water; and Joshua Griffin, Ohio EPA Division of Surface Water

What is a Total Maximum Daily Load or TMDL?

When a stream or lake is not meeting the expectations for a healthy waterbody it is considered impaired and the clean water act requires that a plan is developed to restore it to a healthy state. The plan is called a “Total Maximum Daily Load” or TMDL. A TMDL identifies the linkages between the impairment and a pollutant, then prescribes pollutant load reductions needed to restore the waterbody. 

Sources of pollutants are classified under a TMDL as either point sources or nonpoint sources, both of which are evaluated for needed reductions. Point sources include all sources regulated under the National Pollutant Discharge Elimination System (NPDES) permitting program, including wastewater treatment facilities, industrial facilities, and some stormwater from developed areas. Nonpoint sources include all remaining sources of a pollutant as well as natural background loads. Agriculture is considered as a nonpoint source in the TMDL.

What is the process of creating a TMDL and how is the public involved?

The TMDL process in Ohio is a 5-step process that starts well before the pollutants are allocated to different sources. It starts with developing the plan to monitor water quality, then the monitoring data are evaluated to determine if there are any issues, where problems are identified target conditions are established, then modeling is done to relate those target conditions to the sources of the pollutant in the watershed, finally the sources are allocated to ensure target conditions are met. Each step has opportunities to provide feedback which is used to improve the TMDL.


Does a TMDL give Ohio EPA any additional regulatory authority over nonpoint source pollution?

Preparing a TMDL does not give Ohio EPA additional regulatory authority over nonpoint sources of pollution. A TMDL contains “reasonable assurances” that load reductions from nonpoint sources can be accomplished, and this normally identifies practices and activities that are supported through various grant programs and other efforts, including voluntary measures, that reside outside of Ohio EPA. 

Reducing nonpoint source loads under a TMDL involves collaboration between local, state, and federal partners and often includes non-regulatory and incentive-based (e.g., a cost-share) programs. In addition, waterbody restoration can be assisted by voluntary actions on the part of citizens, environmental groups, and other collaborative organizations.


How do I know what is going on with TMDLs and are there any ongoing projects that I should know about?

Visit Ohio EPA’s TMDL webpage, here you can navigate to Ohio’s many watersheds and find information and documents relating to the projects that are ongoing throughout the state. The EPA webpage is assessable at:

Projects are ongoing throughout the state with Ohio EPA’s routine monitoring and assessment program but a unique effort is going on with the Maumee Watershed Nutrient TMDL. You can find information associated with the Maumee Nutrient TMDL here:

If you want to be notified when new documents are released you can subscribe to Ohio EPA’s TMDL listservs at:  


What makes the Maumee TMDL different?

Our existing TMDLs have been developed to address issues we have identified in streams that are typically near sources of pollution, something we have termed “near-field.” Since the early-2000s when many of these TMDLs were developed these streams have been reassessed. The consistent outcome of these evaluations has been documenting substantial improvements in water quality. These have been linked to both point and nonpoint source impairments. Following these efforts, one big success story is the increasing presence sediment sensitive fish in the Maumee watershed, this has been largely contributed to erosion management on the agricultural landscape. With the Maumee TMDL we are shifting our focus to Lake Erie which is quite far from some of the sources of nutrient in the watershed, what we have termed “far-field.” This opens up some opportunities and implementation planning can focus on improvements anywhere in the large watershed.

We already said that there aren’t new regulations on agriculture so what really changes once a TMDL is completed?

TMDLs can help facilitate strategic planning efforts, such as small watershed scale Nonpoint Source Implementation Strategies (NPS-IS). These plans identify the types of practices needed to address the pollutants in the TMDL and look for specific projects that need to be implemented. Projects available in the plans are eligible to receive federal funds through the Ohio EPA nonpoint source program and the Great Lakes Restoration Initiative. The process ensures that agricultural stakeholders are involved, and projects are focused on the practices most needed to restore water quality in the watershed and Lake Erie.

What type of practices can lower agricultural contributions?

In field practices farmers should consider include nutrient management using the 4Rs of rate, source, timing, and placement; addressing erosion with changes in tillage, cover crops or grassed buffers and water management that reduces or filter waters from the field before exiting to ditches and streams. 

What is happening outside the field boundary in ditches and stream can also increase non-point contributions. Where excessive bank erosion exists, notify the appropriate authorities in your county so plans can be implemented. Lowering agricultural contribution can have on-farm benefits such as reduced nutrient cost from increased efficiency, keep topsoil in the field to support crop production, and eliminate gullies that can increase equipment repairs. Ditch design and buffers along banks can reduce ditch maintenance costs. A variety of practices are available to fit different field situations and farmer goals. The Ohio Agriculture BMP Handbook is one source of information on available practices. Cost share programs from federal and state agencies can assist farmers in trying new practices or offset cost of capital projects.

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