In early fall with lower and warmer water levels, river users commonly see algae coating rocks or floating in the Yampa River, in coves and edges of area reservoirs and especially in stagnant ponds of water left over from higher flows.

However, this fall, watershed study groups and some citizens are raising algae alarm bells and asking questions about what appears to a strong presence of algae in the watershed.

Some residents are asking water experts if the toxic level spike from a blue-green algae bloom in early September at Stagecoach Reservoir, which led the state to issue a brief red warning level closure at Morrison Cove, may be a foreshadowing of greater, growing concerns systemwide in the Yampa River watershed.

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“As there are warmer temperatures and less water, this is the risk that we are going to face in the future, and a healthy watershed is more important than ever,” said Jenny Frithsen, environmental program manager at nonprofit Friends of the Yampa, during an Upper Yampa River Watershed Group meeting on Wednesday.

For the first time since the state algae monitoring program was formalized in 2018, an algae bloom caution warning occurred at Elkhead Reservoir in September, said Water Quality Monitoring and Assessment Specialist Ashley Rust with Colorado Parks and Wildlife.

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A current view of the state’s map of algae in waterbodies at COepht.colorado.gov/toxic-algae shows that of the 10 waterbodies listed at a yellow caution level for algae, three are in Routt County including Elkhead, Stagecoach and Steamboat reservoirs.

In August 2020, a red warning level was issued briefly for a toxic spike from an algae bloom at Steamboat Lake.

Rust said algae problems are increased by “warmer water temperature, long summers and more nutrient pollution in the watershed.”

“The pollution and temperatures are making it worse, but we are also looking for it more and have more awareness of the danger,” Rust said Friday.

Significant algae and water discoloration have been especially visible in the Yampa River within the past few weeks starting, in general, from near Fetcher Park and progressing more noticeably going upstream near the confluence of Walton Creek and then upstream of Chuck Lewis State Wildlife Area, Frithsen noted.

“This time of year, water quality issues are exacerbated by low flows and higher temperatures,” Frithsen explained. “Sediment load is likely increased by burn scars, construction sites and restoration sites after heavy rains. Those events also move nutrients downstream. Warmer than usual temperatures, low flows and excess nutrients contribute to algal blooms. Water that has turned ‘pea green’ could be contaminated with an excess of algal growth.”

Supervisory Hydrologic Technician Patricia Solberg with the U.S. Geological Survey said algae was present at very noticeable levels in the river through Steamboat this year during the August sampling. Solberg said the USGS has been testing once annually since 2019 in late summer or early fall for the aquatic indicator chlorophyll-A as well as algae biomass at three sites, including upstream of Stagecoach, in Steamboat and in Milner.

“Routinely this summer we see very small green algae throughout the water column at those sites through Steamboat,” Solberg said.

Earlier this fall Steamboat resident Eric Schmierer submitted questions to Steamboat and USGS officials concerned about the water quality in the Yampa River that flows through the city.

“I was concerned about the amount of algae I saw in the Yampa River between River Park and Rotary Park in Steamboat Springs during August and September,” Schmierer said. “The water ran a pea green color for weeks in this section.”

The USGS has been the major collector of water quality data since 2010, and multiple other agencies, groups and consultants also are conducting water quality testing now in the Yampa River and tributaries. Municipalities, water districts and grants have supported the work financially. Testing is being done through such groups as state parks, Friends of the Yampa, Upper Yampa Water Conservancy District, River Watch of Colorado and Upper Yampa River Watershed Group.

However, a group discussion Wednesday during a meeting of the collaborative Upper Yampa River Watershed Group reinforced the complexity of the growing problems of water quality and algae in the watershed. There are no simple answers.

“The USGS is aware that many waterbodies are experiencing algal outbreaks at higher rates than in the past and are trying to understand what the causes are,” Solberg said. “Long-term data sets can be very helpful in understanding changing systems due to varying inputs or overall shifts in climate patterns.”

Solberg cited another regional example of increased algae in mid-July in the Roaring Fork River flowing through Glenwood Springs of “very noticeable, very long filamentations of algae, very visible throughout the water column.”

“The abundance of algae in waterways is going on statewide,” Solberg said. “It’s a concern to many watershed groups.”

Experts believe toxic cyanobacteria is more common in lakes, reservoirs and ponds than in flowing rivers. Rust advised dog owners to be especially cautious about letting their pets swim in waterbodies with algae blooms present.

“Humans and dogs have different thresholds, and we don’t really know what dogs can handle,” Rust said. “Dogs take in heavier doses, eat algae, lick their fur and are smaller than humans. Dogs can get sicker at lower levels of algae, and algae can change toxin levels pretty quickly.”

State experts remind water users to always look for posted signs advising of toxic algae and for blooms or scum on the water, advising: “When in doubt, stay out.”

For decades, water quantity has been the top focus of regional water managers, but in recent years, water quality has become a rising concern, especially as the climate warms and a growing Yampa Valley community increases pressure on summer water resources.

“The awareness of the issues of water quality is relatively recent because scientifically it is such a bastard of a problem to deal with,” said Bob Woodmansee, Ph.D., a retired ecosystem science professor at Colorado State University who lives near Stagecoach Reservoir.

“When you are talking about water quality in a place that aggregated all the drainage from a surrounding area,” said Andy Rossi, general manager at Upper Yampa Water Conservancy District, “it’s everything that’s going on in the watershed above that point that contributes to what you see there.”

“We are just trying to get our hands around quality data that has a lengthy period of record and is the right kind of data at the right time,” Rossi said. “There is work that still needs to be done.”

In addition to existing watershed health issues such as agricultural activities, runoff from the built environment, erosion sources and recreational use, other factors are contributing to the discoloration and turbidity this summer and fall in the Yampa River. For example, Colorado Parks and Wildlife conducted a river aquatic habitat improvement project scheduled from mid-July through September at upper Chuck Lewis State Wildlife. The agency warned anglers that “water quality will be poor downstream.”

Another contributor is runoff from the Muddy Slide Fire that burned almost 4,100 acres in summer 2021 in the Morrison Creek valley area in South Routt.

“The Muddy Slide Fire burn scar is producing a sediment load in Muddy Creek and Morrison Creek that is propagating into the mainstem of the Yampa,” explained Holly Kirkpatrick, spokesperson for the Upper Yampa Water Conservancy District. “UYWCD is currently working with partners to develop and implement a mitigation plan in this area.”

Citizens asked questions about the toxic level spike of algae that closed Morrison Cove on Sept. 9-13 in the 820-acre Stagecoach Reservoir, Park Manager Craig Preston said. The most common question is if it is safe for people and pets to be in the water. Signs are posted year-round at Stagecoach Reservoir about the potential for algae blooms.

Other citizens in September voiced concerns at the board meeting of the Upper Yampa Water Conservancy District, which owns and operates the reservoir.

“These blooms are the end-product of a very complex set of interactions between increasing nutrient loading, primarily nitrogen and phosphorus, and increasing temperatures due to climate change,” Woodmansee said.

After the toxic spike in algae, the conservancy district and Routt County Public Health officials released educational notices about blue-green algae, with information available at UpperYampaWater.com/blue-green-algae.

For the past two years, the conservancy district has worked with partners to develop a Yampa River Dashboard that will serve as a data hub for water quality, water management, agriculture and recreation in the basin. Emily Lowell, district engineer, said the online dashboard at YourYampaRiver.org is in the final stages set for completion later this fall.

“We are trying to stay ahead of these problems,” Routt County Environmental Health Director Scott Cowman said Wednesday. “These problems aren’t unusual especially in warmer climates, so we are just trying to find out how much of a problem is it here and is there something we can do to stay ahead of it.”

The Upper Yampa River Watershed Group has gradually made progress for more than a decade via grant funding for consultants to gather and compile information on the causes of algae overloads in Stagecoach Reservoir. The latest watershed group report is due out at the end the year, group coordinator Lyn Halliday said Wednesday.

“We are getting closer to the finish line on our extensive work on nutrient loading and algae-related issues,” Halliday said, with the goal to produce actionable mitigation strategies for upstream of the reservoir as well as remediation recommendations for within the reservoir.

Woodmansee is concerned that work related to three proposed housing developments and a golf course for the south side of Stagecoach Reservoir will further add to the nutrient loading and algae problems. He explained the probable cumulative impacts of construction and operation of the residential and commercial projects on the water quality in Stagecoach, a reservoir he notes is listed as impaired by the USGS, Environmental Protection Agency and Colorado Department of Public Health and Environment.

“Everyone down south here is concerned about future development on the area in general,” Preston noted, “on the wildlife, on recreation, on the park especially, on water quality.”