Total Maximum Daily Load

What goes into farmland as additives impacts the whole state, a fact that is easy to forget on the farm-level.

The Total Maximum Daily Load, or TMDL, is the amount of a particular pollutant that can be released safely to surface water per day. TMDLs are set by the state Department of Environmental Quality, and are designed to ensure that state waters continue to meet quality standards.

Larry Oldham, soil specialist with Mississippi State University's Extension Service, said five watersheds, or river basins — the Yazoo; Pascagoula; Pearl; Big Black, Tombigbee and Tennessee; and Coastal Streams Basin — are used in the Mississippi DEQ planning process.

“Landowners, farmers, foresters, cities, industry and nearly every enterprise contributes runoff to the state's surface waters,” Oldham said. “Even in towns, hard surfaces accumulate runoff, gathering it into one central point that enters streams. We are concerned about sediments, nutrients, pesticides and bacteria in runoff entering the water.”

TMDL standards are being revised in Mississippi and the nation, and these changes have the potential to effect every landowner.

“These new standards have far-ranging implications in land management for our generation and generations to come,” Oldham said.

Charles Cooper, ecologist with the U.S. Department of Agriculture-Agriculture Research Service's National Sedimentation Lab in Oxford, recently spoke to agronomists at an American Society of Agronomy meeting at MSU.

Cooper said some industries have wanted to locate in Mississippi but been unable to locate at the site of choice because their discharge would create a TMDL violation. He said agriculture will soon be evaluated like every other potential source of pollution.

“You look at the watershed and everyone's TMDL contribution to it,” Cooper said. “Decisions will be made in the future on how big a piece of the pie you can have, and what to do if you have too big a piece.”

Cooper said lists are kept of waterways with impairments, or unacceptable impurity levels. Mississippi has 2,254 listed impairments in 727 waterways, and 89 percent of these are attributed to agricultural causes. The state also has 83 percent of the nation's pesticide listings.

Cooper said many of these listings are probable, as no data has been collected from the sites. As the state acquires more monitoring data, many sites should be removed from the list.

“We're really challenged in Mississippi with a lot of listings,” Cooper said. “That forces us to be in the forefront, making decisions and taking action.”

‘New standards have far-ranging implications in land management for our generation and generations to come.”

Cooper also noted that pollution does not follow state lines, and neighboring states' listings may rise as more measurements are made.

Cooper and Oldham are part of a team working to establish nutrient criteria for the state based on actual measurements. These criteria could break the state into subregions with different nutrient requirements. Unless in place by December 2003, the state may default to EPA's standard criteria for the region, which will not allow for many variances in the state's waterways.

“EPA will possibly soften their position on the deadline for criteria,” Cooper said. “In recent discussions, they have stated that ‘state's that are making reasonable progress’ will be given more latitude.”

Limiting TMDLs is a problem for everyone, especially farmers. Cooper urged all farmers to know what streams in their area are listed, and help lead recovery efforts for those water systems to improve water quality before it is necessary.

“We need to do a whole lot better with controlling drainage, and we can do a lot at the edge of a field to reduce runoff,” Cooper said. “Look at the cumulative impacts of best management practices. You may have to try two or more things such as no till or low till, cover crops and impoundments, as following one conservation practice may not be enough.”

Cooper said farmers are great environmentalists and already act to reduce pollutants entering the waterways.

“TMDLs won't go away, so implement the changes as you can and have a heightened awareness of the issue,” Cooper said.

Oldham suggested individuals become involved in the periodic public meetings of the DEQ Basin planning process.

Bonnie Coblentz writes for Mississippi State University Ag Communications.

Hide comments


  • Allowed HTML tags: <em> <strong> <blockquote> <br> <p>

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.