Cody Shale, Selenium &

Water Quality

Natrona County Conservation District's water quality program revolves around Wyoming Department of Environmental Quality's Water Quality Assessment and Impaired Waters 303(d) List. This list is required to be submitted to the US Environmental Protection Agency every other year under the Clean Water Act.

As a result of a water quality assessment of surface water throughout the state, in 1998 the Wyoming Department of Environmental Quality (WDEQ) placed the North Platte River on its list of impaired waterways due to high concentrations of selenium. Subsequently, in 2000, several local tributaries of the North Platte were also placed on the Wyoming's impaired waterways list (WDEQ 303(d) List) due to high concentrations of selenium: Casper Creek, Poison Spider Creek, Poison Spring Creek, Oregon Trail Drain, Goose Lake, Rasmus Lee Lake, Illco Pond, and Thirty-three Mile Reservoir. 

Why do we care about Selenium? Selenium is a naturally occurring element. In Wyoming, and throughout the West, the geological occurrence of selenium is widespread, found naturally in volcanic tuff, coal deposits, and marine shale. While it is an important nutritional supplement, which we usually receive in our normal diet, higher intake concentrations can cause health problems in humans, wildlife, aquatic life, and agriculture products. 

In early 2001, NCCD initiated a comprehensive sampling and analysis program in the Kendrick watershed and identified that the concentrations and movement of selenium was directly related to irrigation water conveyance systems and application practices used in the area. Thanks to grants from Wyoming Department of Agriculture (WDA) and WDEQ, this sampling and analysis program continues on a monthly basis.

The Kendrick Watershed Plan, developed in 2005, was a 10-year initiative of the Natrona County Conservation District (NCCD), and was developed to address and reduce these high concentrations of selenium in surface water runoff and ground water migration in the Kendrick watershed. 

The Wyoming Department of Environmental Quality (WDEQ) implemented an assessment project to develop selenium Total Maximum Daily Loads (TMDLs) for impaired waterbodies in the North Platte River Watershed. The purpose of the assessment was to analyze existing data, characterize water quality problems, assess sources, allocate loads, calculate TMDLs, and define management measures for selenium in the watershed.  The selenium TMDL for the North Platte River was developed in accordance with Section 303(d) of the federal Clean Water Act and guidance developed by the U.S. Environmental Protection Agency (US EPA). The TMDL was submitted to the WDEQ in September 2011 and is awaiting approval by the EPA. The TMDL addresses selenium watershed impairments near Casper Wyoming between Alcova Reservoir and the confluence of Muddy Creek with the North Platte River. 

NCCD began implementing the Kendrick Watershed Plan in mid-2008, in cooperation with CAID, NRCS, and local landowners in the watershed, to establish more efficient and effective irrigation water delivery. NCCD investigated and field tested alternative irrigation water delivery systems to reduce selenium migration. Existing scientific studies and local field demonstrations indicated that certain irrigation practices implemented as alternatives to the standard furrow (flood) irrigation, decreased selenium migration through the soil and to runoff drainages and groundwater.

Several landowners volunteered to employ these new irrigation methods and participated in ongoing water sampling to assess the effectiveness of the alternative methods. NCCD's sampling data is analyzed yearly and compared to previous data from the same sample sites to identify trends and changes in concentrations of selenium over the duration of the Middle North Platte River subwatershed sampling program.

CAID has replaced two sub-lateral open canals with underground pipeline and lined numerous other canals. Two alternative irrigation methods were tested and monitored: Center Pivot and Linear Move Side Roll systems, similar to existing sprinkler irrigation systems. These delivery systems were determined to be the most cost effective and efficient irrigation methods for landowners, while reducing surface runoff to inhibit selenium migration. These methods also reduce water usage, thus conserving a valuable resource.

Nearly 9,000 acres of farm land has been reclaimed for alfalfa production through the transition from furrow irrigation to alternative irrigation methods.