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Serving: OH

How does a TMDL affect agriculture?

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PROTECTING WATER: TMDLs are a tool to help restore and protect bodies of water where aquatic life, recreation, public drinking water or human health are impaired or threatened.
Ask a CCA: A TMDL determines the loading capacity of a body of water and allocation of pollutant sources.

Summer in Ohio has also become the season when numerous news articles and editorials highlight the negative effects agriculture can have on water quality in Lake Erie, Grand Lake St Marys and other bodies of water across the state.

Often in those articles are public calls for more action through rules, regulation, moratoriums and other controls on agriculture production practices. In those conversations, Total Maximum Daily Loads determinations are brought up.

To understand what a TMDL is, how to get involved, how having a TMDL might affect agriculture, and if it is something to fear, we asked a few questions of Rick Wilson, Ohio EPA, and an advisory member of Ohio certified crop adviser board: 

What is a Total Maximum Daily Load or TMDL? TMDLs are a tool to help restore and protect waterbodies where aquatic life, recreation, public drinking water or human health are impaired or threatened. Basically, the TMDL development process determines the loading capacity of a waterbody and allocates the load among different pollutant sources.

Sources of pollutants are classified under a TMDL as either point sources or nonpoint sources, both of which receive load allocations. Point sources include such things as wastewater treatment facilities, municipal separate storm sewer systems, and others in the industrial sector. Nonpoint sources include all remaining sources of a pollutant as well as natural background loads.

Reducing nonpoint source loads under a TMDL involves collaboration between local, state and federal partners and often includes nonregulatory 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.

Does a TMDL give Ohio EPA more 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.

What is the process of creating a TMDL and how is the public involved? Ohio has a robust five-step public involvement process for developing TMDLs. Public participation is encouraged in all five key stages of TMDL development process: the project assessment study plan; the biological and water quality report; the loading analysis plan; the preliminary modeling results; and the draft TMDL.

Stakeholders are notified and asked to review and comment on each of the five steps.

Is there flexibility to adjust the implementation strategies under a TMDL? Yes. A TMDL is predominantly a state-delegated program. U.S. EPA reviews TMDL plans, but states take the lead role in crafting and implementing the strategies within a TMDL to meet goals. Using principles of adaptive management, the state works with partners to identify successes and continuously assess and adjust strategies needed for pollutant reductions and water quality improvements. 

What should we know about the Maumee Watershed Nutrient TMDL? The western basin of Lake Erie has impaired public drinking water supply and recreation uses due to harmful algae. Ohio EPA is developing a Maumee Watershed Nutrient TMDL to address these impairments. This Maumee River Watershed far-field TMDL is somewhat more complex than TMDLs covering smaller watersheds with near-field (localized) water quality impairment, because the contributing area of nutrients spans millions of acres and includes numerous sources.

Further, there are dozens of federal, state, local, and academic partners that have worked to assess and research the water quality impairment in the western basin of Lake Erie. Ohio EPA has created a specific webpage for this project to keep the public informed of the process.

What should I do if a TMDL process starts in a watershed where I farm? Be actively involved! The only way to represent your interest, offer solutions you have seen work, and share how practices others are proposing would impact your operation is to be at the table and part of the conversation.

How do I stay informed? Visit Ohio EPA’s Maumee River Watershed webpage at, subscribe to Ohio EPA’s TMDL listservs at, and visit Ohio EPA’s TMDL webpage at

LaBarge is an OSU Extension certified crop adviser.

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