Water quality and quantity is a major concern in the United States.
The U.S. Environmental Protection Agency (EPA) 1996 water quality
inventory report indicated that 40% of the surface waters that were
surveyed were not meeting their designated uses (EPA, 1998).
models are one of the best tools for analyzing water quality issues.
Models can replicate the flow of pollutants throughout the watersheds
and can be utilized to evaluate the consequences of management
practices, control measures, and planning decisions. Using a modeling
approach for evaluating conservation practices is
cost-effective and timesaving, compared to field monitoring.
Atrazine, a systemic herbicide that blocks photosynthesis, is currently
one of the two most widely used agricultural pesticides in the U.S. It
is also the most commonly detected pesticide in ground and surface
water. Atrazine’s frequent detection in streams, rivers, groundwater,
and reservoirs is related directly to both its volume of usage and its
tendency to persist in soils and move with water.
Since 1999, the Texas State Soil and Water Conservation Board (TSSWCB)
has been working through the (EPA) §319(h) grants program to reduce
nonpoint source pollution from agricultural activities in the seven
watersheds in this project. Technical and financial assistance was
provided through the local Soil and Water Conservation Districts (SWCDs)
for development and implementation of water quality management plans.
The goal of this project was to use computer models and geographic
information systems (GIS) to simulate the effects of applying best
management practices on atrazine loadings in seven Texas watersheds.
Little River Watershed
(PDF; 10 MB) - from the release points
of lakes Belton and Stillhouse-Hollow to the junction with the
The Soil and Water Assessment Tool (SWAT) was used to quantify the
effects of applying conservation practices on atrazine loadings to streams, rivers, and
lakes in each watershed. The Natural Resources Conservation Service (NRCS)
Water Resources Assessment Team (WRAT) located at the Blackland Research
and Extension Center (BREC) conducted the model simulations.