Managing for Algal Toxins in Reclamation's Reservoirs
* How can Reclamation responsibly manage for cyanobacteria and cyanobacteria toxins that potentially may be a threat to aquatic life, human health, and drinking water in reservoirs?
* Will an investigation of cyanobacteria toxins in the Colorado-Big Thompson Project
(CBT), Colorado, lead to responsible decisionmaking when it comes to managing reservoir operations and water delivery?
* Can we develop methods for cyanobacteria collections, toxin identification, and management strategies that can be used on Reclamation-wide reservoirs?
* Will reservoir operations affect cyanobacterial toxins in reservoirs and in downstream releases?
Need and Benefit
A Nutrient Technical Advisory Committee, formed in 2005 and comprised of City of Fort Collins, City of Loveland, City of Greeley, State of Colorado, Reclamation, U.S. Geological Survey, Grand County, Big Thompson Watershed Forum, Northern Colorado Water Conservation District, and Tri-Districts, focused on water issues for the CBT listed one of the top priorities as cyanobacteria blooms and blue-green toxins in the CBT project. Existing capabilities either by Reclamation or other Federal, State, or city agencies to detect blue-green toxins and implement a management plan are presently nonexistent for Colorado. During the summer of 2004, Grand County Water Information Network (GCWIN) detected algal toxins on the Western Slope in Shadow Mountain Lake and Grand Lake, Colorado in Grand County, Colorado and requested Reclamation's assistance with collection of cyanobacteria toxins. Whether or not algal toxins were present in eastern slope reservoirs during summer 2004 is unknown. Generally, at low level densities, cyanobacterial blooms do not present a health risk to human or animals; however, the algal toxin issue has come to the forefront since last summer's investigations. If toxins are found at high densities, often a reservoir may be closed down until blue-green toxin densities decrease. If these toxins were to be diverted from Colorado's Western Slope via the Adam's west portal tunnel to the Eastern Slope, they may impact reliability of Reclamation's water deliveries.
Cyanobacterial or blue-green algae blooms in reservoirs are a common occurrence that are caused by a number of factors that include nitrogen, phosphorus, light, temperature, turbidity, and storm events. However, turbulence and high water flows appear to limit their growth. All cyanobacterial blooms are potentially toxic and may produce cyanobacterial toxins. Both hepatotoxins (microcystins) and neurotoxins are produced by cyanobacteria found in surface water supplies. Hepatotoxins are more widespread in water supplies and are becoming more of a nuisance in Reclamation's reservoirs. Some of the most commonly occurring cyanobacterial species associated with poisonings are Anabaena, _Aphanizomenon_, _Microcystis_, _Oscillatoria_, and _Nodularia_.
Historically, the CBT reservoirs have been classified as mesotrophic with increasing eutrophication in the watershed. As water is pumped back and forth from Lake Granby to Shadow Mountain Lake to Grand Lake and back again, there is a real possibility that cyanobacteria toxins may be diverted through reservoir operations and then transported from the western to eastern slope reservoirs via water deliveries. Developing a program for screening, identifying, and managing for algal toxins would benefit Reclamation's reservoirs and lessen water conflicts in the future.
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This information was last updated on May 4, 2015
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