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| Agricultural Chemical Transport (ACT) in Maple Creek Watershed |
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U.S. Geological Survey (USGS) is studying five watersheds across the
Nation to better understand how natural factors and agricultural management
practices (AMP's) affect the transport of water and chemicals. Natural
factors include climate and landscape (soil type, topography, geology),
and AMP's include practices related to tillage, irrigation, and chemical
application. The study approach is similar in each watershed so that
we can compare and contrast the results and more accurately predict
conditions in other agricultural settings. |
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Why
study the Maple Creek watershed?
Maple Creek and four other watersheds represent nationally important agricultural settings
(chemical use, crops, and AMPSs) and natural settings (climate,
geology, topography, and soils). Maple Creek, which is part of the
Elkhorn River watershed, is representative of corn and soybean row
cropping in the upper Great Plains.
Other features of the watershed
that are relevant to this study:
- Use of agricultural chemicals: Chemicals used
include herbicides such as atrazine, alachlor, acetochlor, metolachlor,
and glyphosate; and fertilizers, both organic and inorganic.
- Distinct natural setting: The rolling upland
hills and a permeable surficial aquifer overlain by less permeable
glacial till allow water and chemicals to move overland to streams
and into Maple Creek. The relatively flat valley bottom lands
and wooded riparian zones along Maple Creek reduce runoff from
fields.
- Variety of agricultural management practices: AMPs
include tillage and no-tillage; use of central pivot irrigation;
maintenance of grassy waterways and riparian buffer zones; construction
of storm retention ponds.
- Water-quality issues: Herbicides and nutrients
have been frequently detected in eastern Nebraska surface and
ground water, including in drinking-water wells (findings of USGS
studies since the 1990's).
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Study objectives
- Understand the links between the sources of water and agricultural
chemicals (nutrients and pesticides) and their behavior and transport
through the environment.
- Predict the behavior and transport of water and agricultural
chemicals in other agricultural areas not being studied.
- Evaluate what the study results mean for management of water
and water quality in a variety of agricultural settings.
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We appreciate
your help
We thank the local growers and land owners for allowing us access to study sites.
We also appreciate the information that has been provided about the watershed and about current as
well as historical agricultural management practices---past practices
also affect concentrations of agricultural chemicals in ground and
surface water.
We will report the findings
of the study in public meetings and in publications. These findings
will provide information that will be useful for improving agricultural
management locally and nationally, and will guide future studies
in other watersheds. |
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Figure 1.  |
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At
a typical study site, several methods are used to collect water
and chemical samples from the air, soil, surface water, and ground
water.
After being applied to the land surface,
agricultural chemicals can move upward into the atmosphere, downward
through the soil to shallow ground water and underlying aquifers,
eventually discharging to streams, or run off across the land into
streams, eventually moving downstream to reservoirs and coastal
waters. This process can take days, weeks, or even decades if water
moves underground through the ground-water system. |
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| Data
Collection in the Maple Creek Watershed, 2003-2004 |
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What
kind of data |
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Why
the data are collected |
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How
often |
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| Meteorological data,
including rainfall, wind speed, solar radiation, and air temperature.
Soil temperature and moisture |
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| Amount of streamflow at Maple Creek
near Nickerson, NE, gaging station and at unnamed tributary
to the South Fork of Dry Creek near Schuyler, NE |
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| Quality of stream water, runoff water,
rain water* |
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| Ground-water levels in wells |
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| Quality of water in and around streambed. |
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| Quality of ground-water and surface water below agricultural fields* |
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| To determine amount of
precipitation and how much water from land surface reaches the
water table, how much is lost to evapotranspiration |
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| To interpret water-quality data correctly
(the amount of water in streams affects chemical concentrations) |
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| To quantify the transport and behavior
of natural and agricultural chemicals |
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| To determine direction of ground-water
flow, which affects transport of chemicals |
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| To quantify the transport and behavior
of natural and agricultrual chemicals |
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| To quantify the transport and behavior of natural and agricultrual chemicals |
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| Continuously for 3 years (2003-2005) |
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| Continuously since 1951 at Maple
Creek (real-time data available here).
Continuously from May 2003 until September 2004 at unnamed tributary to the South Fork of Dry
Creek |
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| Several times a year (>14 samples)
for 2 years, with intensive sampling during application season (2003, 2004) |
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| At least quarterly in some wells,
continuously in others for at least 1 year (2004) |
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| At least quarterly for 1 year (2004) |
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| At least quarterly for 1-2 years (2004, 2005) |
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| *In this study,
water-quality and data include concentrations of
nutrients (nitrogen and phosphorous), pesticides and pesticide break
down products, and natural constituents and properties, including
major ions (calcium, magnesium, chloride, etc.), organic carbon, dissolved
oxygen, and temperature. |
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Progress as of March 2005
The CNBR ACT team finished sampling for the rainfall, surface water, ground-water/surface-water interaction
and ground-water flowpath portions of the study in 2004. Sampling in the vadose zone began in 2004 will continue in 2005.
The national ACT team will be working on journal articles to synthesize national results for each of the processes investigated during
the study during 2005. Additional publications will also be completed in 2005-2006 to document the environmental setting at each site,
surface-water and ground-water modeling parameters at each site, and the mass balance of water and chemicals for each study unit.
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We
would like to thank
University of Nebraska-Lincoln,
Conservation and Survey Division |
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For more information
Jason Vogel, Lead Scientist, Maple Creek study (402)437-5129, jrvogel@usgs.gov
Paul Capel, Team Leader, National study (612) 625-3082, capel@usgs.gov
NAWQA Program http://water.usgs.gov/nawqa |
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Publication
Frenzel, S.A., and others, 1998, Water Quality in the Central Nebraska
Basins, 1992-95, U.S. Geological Survey Circular 1163 |
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