Selenium, a naturally occurring element that’s widely distributed in rocks, soils, water and living organisms, is most common in the western United States, in such marine sedimentary deposits as the Mancos shale which is common throughout the Uncompahgre Valley.
Some soil types in Montrose County contain relatively high levels of soluble selenium which can be flushed out of the soils and into local waterways. Locally, it has been shown that deep percolation from irrigation, large quantities of groundwater movement, and other sources may increase selenium concentrations in streams, ponds, reservoirs, lakes and wetland areas.
Evidence indicates that high levels of selenium may cause reproductive failures and deformities in fish and aquatic birds. In response to this evidence, the State Water Quality Control Commission adopted a 4.6 parts per billion (ppb) standard for the Gunnison River Basin in July of 1997. Upstream from the major irrigated areas in the Colorado River Basin, including the Gunnison and Uncompahgre River Basins, selenium concentrations are generally less than 1 ppb, but downstream from irrigated areas, the selenium concentrations in surface waters often exceed the state standard. Selenium levels in the lower Uncompahgre and lower Gunnison Rivers have exceeded the 4.6 ppb since the standard was put into place, although the selenium levels in these waterways have been reduced over the past decade.
Action has been taken to reduce the level of selenium in the Uncompahgre Valley and Gunnison Basin. These efforts include lining of canals and laterals by local water providers like the Uncompahgre Valley Water Users Association as well as the formation of many working groups and task forces. The Gunnison Basin Selenium Task Force is one such group that is dedicated to researching and addressing the selenium issue in Montrose and surrounding counties. If selenium standards in the Gunnison Basin continue to exceed state and/or federal standards, there’s a possibility that federal agencies like the U.S. Fish and Wildlife Service may take further action to mitigate selenium.
Residential property owners can individually help to mitigate selenium by following these best management practices:
Avoid overwatering lawns and landscaping.
Line ponds and other water retention features.
Pipe or line open irrigation ditches.
Install efficient irrigation systems with timers.
Consider xeriscaping (landscaping which does not require significant watering).
The Montrose County Planning Commission will continue to monitor and keep citizens and stakeholders informed about this important issue.
A map showing potential selenium concentrations in Montrose County is available on the County website at:www.montrosecounty.net/seleniummap.
For more information on selenium and selenium mitigation please visit the Gunnison Basin Selenium Task Force website at:www.seleniumtaskforce.org.