July 26, 2001
Agricultural Research Service scientists in
Oxford, Miss., have devised a new method for evaluating streams and rivers
impaired by sediment.
Hydraulic engineer Roger A. Kuhnle and geologist Andrew Simon at the
ARS National Sedimentation
Laboratory are focusing on streams with clean sediments free of chemical
contaminants. The two are developing numeric targets for maximum sediment for
streams in different regions, since the amount of sediment a stream can handle
varies greatly in different parts of the country.
The research involves analyzing and compiling previously collected waterflow
and sediment data, along with field data on the stability of a given stream.
Kuhnle and Simon will then develop target values for clean sediment that
correspond to unimpaired streams in other regions.
All streams and rivers have the ability to handle a certain load of sediment
without being damaged, but the difficulty is in estimating that load. Bodies of
water that receive too much sediment potentially require a Total Maximum Daily
Load (TMDL) assessment.
A TMDL is the level of pollution a body of water can tolerate and still meet
water quality standards set by the states, territories and tribes. It also
identifies both appropriate uses for each water body--as, for example, drinking
water supply, contact recreation such as swimming, or aquatic life support--and
the scientific criteria to support such use. Section 303 of the Clean Water Act
establishes the water quality standards and TMDL programs.
Eventually, the new procedure will help identify streams especially
vulnerable to sedimentation. It should also make it possible to relate the
target values for clean- sediment TMDLs to designated uses of the streams and
rivers in different regions.
ARS is the U.S. Department of
Agricultures chief scientific research agency.