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implemented, this success story is based on an
assessment of changes in irrigation methods.
Analysis showed that between 2005 and
2015, the flood-irrigated areas decreased
from 49,751 acres to 42,265 acres, while the
sprinkler-irrigated areas increased consider-
ably from 24,500 acres to 41,250 acres. This
increase in sprinkler irrigated areas exceeded
the reduction in flood-irrigated areas. This
is possibly because the sprinkler systems
provide flexibility and can be used in areas
where flood irrigation cannot (e.g., hilly areas).
Selenium Concentrations in the Middle South Platte Riveras Compared to Standard
9
Results
Implementing sprinkler irrigation systems in
the watershed has been an ongoing process.
Because the listing of the segment was based
on 2003-2007 data, the baseline for the BMP
implementations was set to 2005. Similarly,
the removal of the segment from the CWA
section 303(d) list was based on 2013-2014
data. Therefore, locational data for the irrigation
systems were extracted from 2015, which captured
irrigation changes from 2005 to 2015. Sprinkler
installation that occurred between these years is
clearly demonstrated in the "area enlarged" box on
the left side of Figure 1, where five sprinkler circles
are aggregated in previously non-irrigated area. In the
enlarged area box, sprinkler systems were installed in
areas previously flood irrigated.
Before BMP implementation occurred in this section of
the Middle South Platte River, Se concentrations were
up to 60 percent higher than the table value standard
threshold. Monthly water samples were collected at
sites near Kersey from August 2013 to November 2014.
Most of this sampling was completed voluntarily by
the Colorado River Watch program and Metropolitan
Wastewater Reclamation District. Data at all sampling
sites showed no exceedances of the 4.6 |ig/L WQS for
at least two consecutive years (Figure 2). Colorado
Department of Public Health and Environment
assessed the water quality data according to their
protocols. The dissolved Se concentrations observed in
2013-2014 varied from month to month, but the maxi-
mum concentration was 2.8 |ig/L, which is 61 percent
of the WQS of 4.6 |ig/L. During the 2016 CWA section
•
. ••
•
• i
•
•
•
•
•
State Selenium
WQS -4.6 ug/L
•
• . •
• • •
••
• •
•
j»
I'
. ..
—• • «••
M U-
At
• Selenium
concentrations
that led to the
303(d) listing in
2010
• Selenium
concentrations
that led to
delisting in
2016
0
9/1/2002
9/20/2004
10/10/2006
12/7/2012
12/27/2014
Sample Date
Data collection that led to 303(d) listing completed 2003-2008. Data collection that led to de-listing completed 2013-2014.
Figure 2. Selenium concentrations in the Middle South Platte River
segment (2003-2008 and 2013-2014).
303(d) hearing, the assessment that demonstrated
that the Middle South Platte River was in attainment of
the aquatic life use-based standards for dissolved Se
was submitted to the WQCC. The WQCC agreed and
the Middle South Platte River was removed from the
2016 CWA section 303(d) list for attaining the Se WQS.
Partners and Funding
NRCS Environmental Quality Incentives Program
funding in Weld County from 2005 to 2015 totaled
$11,588,730. The watershed area under investigation
covers approximately 7.5 percent of the county; BMP
funding costs were calculated at about $878,208.
The cost sharing requirement for the producers
was approximately 25 percent of the BMP costs, or
$219,552, so the total funding spent in the area is
estimated at $1,095,760. This total does not include
private funding spent on BMP implementation,
including sprinkler systems. Based on the increase in
the sprinkler-irrigated areas alone, the private funding
could be several million dollars. In the end, voluntary
efforts, which are essential and necessary in control-
ling NPS, helped to address Se pollution in the Middle
South Platte River.
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U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA 841-F-19-001FF
November 2019
For additional information contact:
Colorado Department of Public Health and Environment
Kenan Diker • 303-692-3597 • kenan.diker@state.co.us
Bonie Pate • 303-692-3557 • bonie.pate@state.co.us
Christa Trendle • 303-692-6343 • christa.trendle@state.co.us
Estella Moore • 303-692-2864 • estella.moore@state.co.us
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