Algae bloom research at Cheney Reservoir supports better-tasting, safer water
Just ahead of the Fourth of July weekend, Cheney State Park shut down its swim beaches due to the potential presence of toxic algae in the water.
More than a week later, people are still asked not to swim, wade, ski, use jet skis or allow pets in the water at Cheney Reservoir.
Algae blooms are a frequent summer occurrence in Cheney, and other Kansas lakes such as Marion County Lake. The blooms are caused by the rapid growth of blue-green algae, also called cyanobacteria.
Cyanobacteria turn the lake water scummy, produce toxins that can sicken humans and pets, and infamously cause Wichita tap water to taste and smell like dirt.
Studying the blooms has been a top priority for scientists at the U.S. Geological Survey’s Kansas Water Science Center for nearly 25 years. Their long-term efforts to understand algae blooms have had far-reaching benefits, leading to better tasting tap water here in Wichita, safer lakes across the country, and training a new generation of water scientists.
Faster water treatment during taste and odor events
Most Wichita residents are all too familiar with signs of an algae-related taste and odor event at Cheney Reservoir, the main water source for the city.
“The water smells musty, or dirty, or maybe moldy,” said Ted Harris, a research assistant professor at the Kansas Biological Survey and former hydrologic technician at the Kansas Water Science Center. “There’s this bouquet of smells that comes out of it.”
The culprit is a compound called geosmin that is released by some algae blooms. Geosmin isn’t toxic, but its flavor packs a powerful punch – humans can sense a concentration of geosmin equivalent to five to 10 drops of water in an Olympic-sized swimming pool.
When algae blooms began befouling the taste and smell of Wichita water in the early 1990s, the USGS Kansas Water Science Center formed a partnership with the city to monitor water quality in Cheney Reservoir and the surrounding areas.
Since 2001, specialized sensors in Cheney Reservoir have been collecting measurements such as water temperature, pH, and turbidity - a measure of how much sediment is in the water - all of which are publicly available. Scientists also periodically collect water samples from the reservoir for more detailed laboratory analyses.
Early research determined that runoff containing agricultural fertilizer, particularly the nutrient phosphorus, was one of the main contaminants in Cheney Reservoir. Over 99% of the watershed feeding into Cheney Reservoir is agricultural land, and farmers commonly use phosphorus fertilizer because it supports crop growth. However, phosphorus can also be washed into nearby streams when it rains and eventually reach the reservoir, where it ends up feeding algae instead of crops.
Ever since the phosphorus problem was identified in 1994, groups like Cheney Lake Watershed Inc., a farmer-led non-profit organization, have been working with farmers in the region to reduce their nutrient runoff by improving agricultural practices. Though they’ve made progress, the amount of phosphorus entering Cheney Reservoir still exceeds water quality goals.
“What we know is that blooms happen in systems that have a lot of nutrients, and where the temperatures are very warm. That pretty much means every single lake or reservoir in Kansas,” Harris said. “But only under certain conditions do they really prompt these blooms.”
Continuous water quality monitoring allows scientists to figure out what those conditions are, so algae blooms can be predicted and managed.
One welcome result is the development of a computer model that predicts the probability of geosmin concentrations rising to a level that human taste buds can detect, based on real-time measurements of the reservoir water pH.
Due to frequent seasonal taste and odor problems, in 2007 the City of Wichita constructed a $7.5 million water treatment facility at the Cheney pumping station.
The water pumped out of the reservoir is now continuously treated via ozone injection, which disinfects the water and removes contaminants causing taste and odor problems, including geosmin. Because treatment takes place at the reservoir pumping station it can take up to four days for treated water to travel roughly 30 miles through the pipes and reach your tap.
Using the USGS model, the city’s Department of Public Works and Utilities can proactively increase ozone treatment to improve the taste and smell of the water when the probability of detectable geosmin predicted by the model gets too high. Though predictions aren’t always perfect, this tactic results in better-tasting water faster than if the city had to wait for complaints of funny-tasting water to begin treatment.
Local and national impacts
Cheney Reservoir is also playing a major role in a nationwide effort to rapidly detect algae blooms using satellite data.
This “early warning system” would allow for faster detection of harmful algae blooms, enabling officials to quickly close affected lakes and prevent swimmers and boaters from being exposed to toxins often released by cyanobacteria. A recent study found that employing this technology saved about $370,000 in healthcare costs following an algae bloom event in Utah Lake, outside of Salt Lake City.
Major federal research agencies including the National Aeronautics and Space Administration, the National Oceanic and Atmospheric Administration, the US Geological Survey, and the Environmental Protection Agency, are involved in the project.
Water quality and blue-green algae data measured at Cheney Reservoir will be compared to the maps of cyanobacteria predicted with satellite data. This type of validation, called “ground-truthing,” is critical for ensuring accurate predictions of algae blooms.
“The lake gains the notoriety to be included in this kind of project because of our long-term cooperation and partnership with the City of Wichita, and being able to collect such a wealth of data for the lake,” said Ariele Kramer, a hydrologist at the Kansas Water Science Center who currently leads the Cheney Reservoir monitoring work.
Partnership with Maize High
Understanding the causes behind cyanobacteria blooms at Cheney Reservoir is the first step towards preventing them. This research is a collaborative effort, and it doesn’t just involve professional scientists.
Students in Maize High School’s Climate Club have been working with Harris and USGS scientists to study how water temperature affects the formation of harmful algae blooms. They were awarded best undergraduate oral presentation at the 2019 Great Plains Limnology Conference, despite still being in high school. They’ve also presented their work at the Kansas Governor’s Water Conference, and the Microbiomes of Aquatic, Plant, and Soil Systems across Kansas Research Symposium.
Harris hopes that getting involved in water quality research will inspire the students to follow their interests and continue working to protect one of Kansas’s most valuable natural resources.
“It costs so much to treat our water, and it’s so important to all life on earth,” Harris said. “You don’t have to have a PhD to make a difference. All you have to do is your best.”
This story was originally published July 15, 2020 at 5:01 AM.