An increase in water flow has caused phosphorous concentrations in the Illinois River watershed to rise, according to a state natural resources official.
For decades, the phosphorous concentration in the Illinois River and its tributaries has been declining, but the five-year average for 2013-17 rose in at least four bodies of water, according to a report presented to state officials in September.
Overall there’s still a major decline in phosphorous concentrations in water, although the amounts remain above what Oklahoma considered the maximum allowed, said Ryan Benefield, deputy director of the Arkansas Natural Resources Commission.
What’s different about recent years is that the water flow is faster, Benefield said, which means the water carries in more sediment through runoff and stream-bank erosion of soil contaminated with “legacy” phosphorus. “Legacy” means the phosphorus remains from a past land use.
Increased rainfall has increased river flows, Benefield said.
Rainfall in Fayetteville has been higher in recent years after nearly a decade of average precipitation, said Nicole McGavock, a hydrologist and meteorologist with the National Weather Service in Tulsa. Before that, precipitation fluctuated between higher and lower than average.
Flow in certain creeks has increased since 1981. The worst phosphorous-loading occurred in the middle of the first decades of the 2000s. While changes in phosphorous-loading correlate with changes in water flow, changes in phosphorous concentrations generally don’t.
During drought-plagued 2012, Benefield noted, when water flow was much lower, the phosphorous concentration was 0.070 milligrams per liter in the Illinois River south of Siloam Springs. In 2017, when there was higher water flow, the concentration was 0.043 milligrams per liter.
Phosphorous-loading increased in Flint Creek, Sager Creek and part of the Illinois River, according to the report, which was compiled through 2017. Phosphorous loading went down in Baron Fork.
In Flint Creek, loading rose from an average of 1,761 kilograms per year from 2012-16 to 1,946 kilograms per year from 2013-17. That change was 3,789 kilograms to 5,083 kilograms in Sager Creek and 33,473 kilograms to 45,502 kilograms in the Illinois River south of Siloam Springs. Loading in Baron Creek dropped from an average of 1,276 kilograms per year from 2012-016 to an average of 1,193 kilograms per year from 2013-17.
Those aren’t the first times phosphorous-loading has increased in those spots.
The 2017 phosphorous concentration in Sager Creek was 0.473 milligrams per liter, down from 2.125 milligrams per liter in 1981.
The lowest concentrations were in Baron Creek. The 2017 phosphorous concentration was 0.039 milligrams per liter, down from 0.135 milligrams per liter in 1981.
Data for Flint Creek were not available.
The standard in Oklahoma, at Watts where the Illinois River crosses the state line, is 0.037 milligrams of phosphorus per liter.
Ed Brocksmith, a founder of Save the Illinois River in Tahlequah, Okla., said he believes rainfall was the culprit for the phosphorous concentrations increasing. But he is concerned about the growth of poultry facilities in Northwest Arkansas and northeast Oklahoma, where much of the river’s watershed is located, he said.
“We’re going to see more poultry waste reported,” he said. “That’s one of the things we’d like to know is where it is going.”
Brocksmith has campaigned for a Total Maximum Daily Load Study on the Illinois River and its tributaries, which at some point could trigger stricter requirements for discharge permits into those waterways.
In October, U.S. Environmental Protection Agency Region 6 Administrator Anne Idsal said in a speech at the Arkansas Environmental Federation’s annual conference that the agency was leaving a total maximum daily load study on the table but was not pursuing it as a solution to the Illinois River’s problems.
Idsal said she was confident that the parties involved in continuing negotiations — representatives of the EPA, Arkansas, Oklahoma and the Cherokee Nation — would reach a solution to improve the waterways.
On Wednesday, Oklahoma and Arkansas signed an agreement to maintain Oklahoma’s standard of phosphorus in its scenic waters at 0.037 milligrams per liter, after a Baylor University and committee study recommended a 0.035 milligrams per liter concentration. The agreement lowered the limit of what wastewater plants can discharge into the watershed but kept the level above what previous wastewater plants were required to meet.
Nicole Hardimann, executive director of the Illinois River Watershed Partnership, said she is unsure why phosphorous concentrations had increased but she is proud of the progress made so far in reducing phosphorous concentrations since the 1980s.
“These reports are so important over time to see where the trend is headed,” she said.
The state is still below the 40 percent phosphorous reduction goal, Benefield said.
“In each of these cases, all of our overall trends are still very good.”