Extension Communications
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915
1/2/02
Contacts:
Mahdi Al-Kaisi, Department of Agronomy, (515) 294-1923, malkaisi@iastate.edu
Bill Ehm, Iowa Department of Natural Resources, (515) 281-8143
Del Marks, Continuing Education and Communication Services, (515) 294-9807,
delmarks@iastate.edu
FOR IMMEDIATE RELEASE
Sediment and Total Maximum Daily Loads Affect Water Quality
AMES, Iowa -- Most producers of Iowa agricultural commodities know that soil erosion can have a substantial effect on water quality. Now there is something new to consider -- sediment-based TMDLs (Total Maximum Daily Load).
Bill Ehm of the Iowa Department of Natural Resources (DNR) says that when a TMDL is developed it identifies the adverse impact that a pollutant (such as sediment, nutrients, or pathogens) has on a water body. Then it calculates the maximum amount of that pollutant that a water body can receive and still meet water quality standards. Water quality standards are usually determined by the intended use of the water body -- known as "fishable, swimable, drinkable."
Mahdi Al-Kaisi of the Iowa State University Department of Agronomy says that producers need to start thinking about the concept of TMDLs when making conservation plans and erosion control decisions. "Producers need to take an active role in managing their watersheds and work closely with their neighbors in addressing sediment transport and soil erosion control based on a watershed approach."
"After the maximum amount has been determined," says Ehm, "watershed allocations for sediment can be developed. It's still too early to conclude, but for producers with farmland within impaired watersheds (which would require the development of a TMDL), designating allocations for sources within the watershed could mean converting highly-erodible row crop fields to a sod-based crop, changing tillage practices, and applying manure and fertilizer according to a set of best management practices."
Is sediment really a TMDL problem? Ehm says that of the more than 200 distinct types of impairments identified by the Environmental Protection Agency (EPA), sediment is listed as the number one pollutant. "Sediment and soil loss compounds other water quality problems, such as phosphorous, nitrate, and other nutrient pollution."
What do TMDLs mean to Iowa producers? Al-Kaisi says that the EPA and Iowa DNR are looking at ways to apply the TMDL model to agriculture in Iowa. "Basically, keeping sediment out of water bodies means limiting erosion. That means producers consider all the soil conservation techniques you can think of, for example, conservation tillage and no-till, terraces, grass waterways, riparian buffers, best management practices and nutrient management plans, and taking steps to reduce pasture erosion."
For more information contact county soil and water conservationists or you can go to the Iowa DNR's TMDL program site at: www.state.ia.us/dnr/organiza/epd/wtresrce/303dnotc.htm. For more information on TMDLs in general, go to the EPA site: www.epa.gov/owowwtr1/tmdl/. Examples of approved sediment TMDLs can be found at: www.epa.gov/owow/tmdl/examples/sediment.html.
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Funding support provided by USDA Natural Resource Conservation Service through Cooperative Agreement No. 74-6114-0-2.
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