Benchmark selenium levels reached in Gunnison River, easing pressure on water users and assisting recovery of endangered fishes
Delta, Colorado — The Lower Gunnison River reached an important milestone in the summer of 2021. During its June hearing, the Colorado Water Quality Control Commission deemed the Gunnison River in compliance with aquatic life standards for dissolved selenium – a naturally occurring element and micronutrient that can be unhealthy for aquatic ecosystems in high doses. As a result, the Commission delisted 66 miles of the Gunnison River downstream of Delta, Colorado from the impaired waters list. Decades of work in the Lower Gunnison Basin shepherded this achievement, which highlights a healthier environment for native and endangered species like the razorback sucker and the Colorado pikeminnow.
“This is a big victory and a reason to celebrate,” says Raquel Flinker, Senior Water Resources Engineer with the Colorado River District. “The Colorado River District has been a leader in this effort for over 20 years, working alongside multiple partners including the Bureau of Reclamation, the Colorado Water Conservation Board, the Natural Resources Conservation Service, the U.S. Geological Survey, non-governmental agencies, local conservancy districts, ditch companies, and even individual citizens to reach this point.”
Established and led by the Colorado River District as part of the cooperative Selenium Management Program, the Lower Gunnison Project (LGP) has proved instrumental in the final phases of the delisting. The decades of associated work began with the 1988 listing of the Gunnison River as an impaired water, with selenium levels as a focal point. Prevalence of the element results from the area’s marine-derived Mancos Shale, which contains vast amounts of selenium and releases it into ground and surface waters when saturated. Gunnison River Basin selenium levels had increased to such unhealthy levels that the reproductive abilities of egg-laying species – including native fish and birds – were impaired throughout the local ecosystems.
In response, the LGP was formed to address this and other natural resource issues in the Gunnison River Basin by investing in integrated water-use efficiency systems. Investments included enclosing canals and ditches into pressurized piping systems and upgrading irrigation equipment on farms with improved technology control. All together, these systems decreased water losses and minimized selenium-impacted runoff to the river resulting in better water quality and increased water availability. In 2020, the 5-year level of selenium measured at key stations in the river dropped below 4.6 ppb (parts per billion) for the first time, and the declining trend continues, as quantified by independent scientific agencies like the USGS.
“A lot of the credit goes to the local water users, especially the agricultural community,” said Ken Leib, Acting Director of the Colorado Water Science Center during the River District’s Gunnison State of the River event in June. “Often, lower flows in the river, as we are seeing today, result in higher concentrations of selenium. But despite drought conditions, we are not seeing that. So, we are really confident that the decreases we see have resulted from improvements in system efficiencies. It’s really quite impressive.”
Colorado River District Director of Science and Interstate Matters Dave “DK” Kanzer, creator of the Lower Gunnison Project, has been a long-time, integral leader in the Selenium Management. “We’re making a big difference for the environment by improving water quality and the aquatic habitat for sensitive and endangered species, while helping sustain productive agriculture in the Gunnison and Colorado River Basins,” he said. “Investments in strategic structural improvements and increased public education have moved us into full Clean Water Act compliance while helping take another step towards recovering key threatened and endangered fish species. This takes a lot of pressure off our hard-working agricultural producers; it is an important win-win for everyone.”