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Irrigation Practices Restore Water Quality in the North Platte River
Waterbody Improved lrr'§ation of cropland overlying cretaceous shale formations
contributes to high selenium concentrations in the North Platte
River near the city of Casper. In 1998, the Wyoming Department of Environmental Quality (WDEQ)
added a 36.8-mile segment of the river to the Clean Water Act (CWA) section 303(d) list due to
aquatic life, coldwater fisheries, and wildlife designated uses being impaired by selenium. Voluntary
restoration efforts led by Natrona County Conservation District (NCCD) in cooperation with many
partners have reduced selenium loading to the river from irrigated cropland activities. The segment
of the North Platte River now meets the selenium water quality criterion, and WDEQ has removed it
from the impaired waters list in the 2016/2018 305(b)/303(d) Integrated Report.
Problem

The North Platte River through the city of Casper is an
important waterbody protected for drinking water,
fisheries, aquatic life, and other designated uses
(Figure 1). Studies in the 1990s in the irrigated crop-
land area west of Casper found high concentrations of
selenium in plants, soils, water, sediment, and biota,
which was thought to have impaired reproduction and
caused embryonic deformities in migratory aquatic
birds. Although natural background loading of selenium
to surface waters has occurred from soils and bedrock
composed of marine shales, studies indicated that natu-
rally occurring selenium dissolves from soil during irriga-
tion and is returned to surface waters through excessive
drainage water. As a result of high selenium concentra-
tions, WDEQ added a 36.8-mile segment of the river to
the 1998 CWA section 303(d) list of impaired waterbod-
ies due to aquatic life, cold water fisheries, and wildlife
designated uses not being supported.
Want to Dive into Details?
The North Platte River's In-Depth Success Story page
(under development) explains the keys to success,
including:
•	Dedicated local leaders who
educated and encouraged others
•	Enterprising and enthusiastic
farmers who were early-adopters
•	Economic benefits realized
through water and labor cost-
savings
Figure 1. Map of the North Platte River watershed project area.
Story Highlights
Lisa Ogden, NCCD
Locally led restoration activities and monitoring began
in the mid-1990s and continue today. CWA section 319
funding initially contributed to these restoration activi-
ties through four projects between 2001 and 2011.
The total maximum daily load (TMDL.) development
process, initiated by the WDEQ in 2009, resulted in a
watershed-based plan. NCCD received additional sec-
tion 319 funds in 2012 to continue restoration activi-
ties, following recommended action items in the plan.
Due to NCCD's leadership as well as key partnerships
developed with other entities (e.g., Natural Resources
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Figure 2. Landowners installed practices such as pivot
sprinkler irrigation.
Conservation Service, city of Casper, Natrona County,
Casper Alcova Irrigation District [CAID], and numerous
landowners), this project implemented an impres-
sive number of best management practices (BMPs)
between 2012 and 2016. During this four-year period,
voluntary cost-share assistance projects resulted in a
total of 726 acres converted from flood to sprinkler
irrigation and 29,569 feet of underground pipeline
installed to replace 35,519 feet of open ditch (Figure
2). In addition, 12 livestock/wildlife watering projects
were completed using other funding sources.
This project also included education and outreach
efforts, including annual meetings with the city of
Casper, Natrona County, and elected officials; meetings
with landowners and CAID; and the publication of edu-
cational booklets about land management activities
and selenium. NCCD received additional section 319
funds in 2015 which, along with other funding sources,
has allowed landowners to convert an additional 495
acres from flood to sprinkler irrigation and 29,854 feet
of dirt ditch to 21,661 feet of pipeline.
Results
NCCD collected monthly data along the North Platte
River and tributaries within the Kendrick Irrigation
Project Area (Kendrick Project). Monitoring objec-
tives included determining whether the impaired
river segment was meeting the chronic water quality
criterion for selenium (5 micrograms per liter [[ig/L]).
Monthly data collected between January 2010 and
December 2013 at two sampling sites—the upper (site
NPR1) and lower (site NPR2) extents of the impaired
segment—revealed that selenium concentrations were
at or below 5 [ig/L. However, due to the importance
of the river as a cold-water fishery and a highly visible
resource within the Casper community, coupled with
limited information on total selenium concentra-
tions within the 25 river miles separating NPR1 and
NPR2, WDEQ recommended that additional sites be
monitored.
Per WDEQ's recommendation, NCCD began monthly
sampiing at three additional sites (NPRRR, NPRPP, and
NPRCR22) in 2014 whiie continuing monthly sampiing
at NPR1 and NPR2. Data at ail sites have indicated no
exceedances of the 5 |ig/L criterion for at ieast two
consecutive years. Furthermore, mean total selenium
concentrations at ali sites for data avaiiabie between
July 2014 and August 2017 were less than or equal
to 2.7 |ig/L Finally, data from 2010-2017 in combina-
tion with historic 2003-2009 data collected by NCCD
at sites within the Kendrick Project showed a statisti-
cally significant reduction in project-wide average
selenium concentrations. Therefore, the WDEQ has
removed the 36.8-mile impaired segment of the North
Platte River from the 303(d) list with the 2016/2018
305(b)/303(d) Integrated Report.
Partners and Funding
Local voluntary efforts helped to address nonpoint
source pollution. NCCD's leadership, a strong part-
nership with the Natural Resources Conservation
Service (NRCS), and landowner participation were
instrumental to the project's success. A total of
$1,129,292 in CWA section 319 funding has been
contributed to these projects to date, and the NCCD is
looking at additional projects to address high sele-
nium concentrations in tributaries to the North Platte
River. State, local and private funds have contributed
$1,303,150 towards the projects; notably, partnerships
and outreach under these projects prompted the city
of Casper and Natrona County to both contribute fund-
ing to assist with BMP implementation. NRCS funding
has contributed $640,908 in cost-share assistance to
the projects to date. Project partners included the
city of Casper, Casper Public Utilities Board, Natrona
County Commissioners, Natrona County Weed and
Pest, Wyoming Association of Conservation Districts,
University of Wyoming Extension Service, NRCS,
CAID, U.S. Department of Agriculture Farm Service
Agency, Wyoming Department of Agriculture, WDEQ,
Wyoming Water Development, and Wyoming Game
and Fish Department.
U.S. Environmental Protection Agency
Office of Water
Washington, DC
W .1
^ EPA 841-F-18-001Y
pRot^° October 2018
For additional information contact:
Lisa Ogden
Natrona County Conservation District
307-261-5436 • Lisa.Ogden@wy.nacdnet.net
Jennifer Zygmunt
Wyoming Department of Environmental Quality
307-777-6080 • jennifer.zygmunt@wyo.gov

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