Fall 2009 » Research Briefs » Illinois River Standards "Unrealistic," Researcher Says

Illinois River Standards "Unrealistic," Researcher Says

March, 2009

As the controversy surrounding the Illinois River water quality heads into court, researcher Marc Nelson has determined that, although some improvements can be made, the phosphorus levels set by Oklahoma are unrealistic within the next decade.

"We wanted to look at the science and address the information gap between what we know and what we don't know," explained Nelson, assistant director of the Arkansas Water Resources Center. "Mass balance analysis is common in engineering and has often been used in watershed studies, but when I started looking for the data for the Illinois River, I found that no one had ever done a mass balance for this system."

A mass balance analysis is similar to balancing a checkbook. In a checkbook, people record deposits and withdrawals to track how much money is in the account. In a mass balance analysis, researchers monitor the inflow and outflow in a system. A watershed analysis determines if the watershed is accumulating nutrients or whether it is passing them downstream via its rivers.

The researchers found that although point-source discharge is only 3 percent of the total input, it accounts for 43 percent of the phosphorus in the Illinois River, while non-point sources account for 57 percent of the total.

"This is very different from previous assumptions," said Nelson. "Past analyses have always assumed that since point sources represent 3 percent of the input, they also represent 3 percent of the output. But we found that is not the case at all. This means that a great deal of the non-point source phosphorus is remaining in the watershed."

Nelson calculated the rate change in phosphorus levels in the Illinois River and determined that if phosphorus levels continue to rise at present rates, then in 10 years total phosphorus content will have doubled from present levels.

"Application rates are increasing and the phosphorus levels are continuing to rise because of this huge reserve in the watershed," said Nelson. "Although total phosphorus levels could be dropped by one-third by limiting point-source discharges to 1 mg/l, meeting Oklahoma's arbitrary 0.037 mg/l requirement is not a realistic goal within the next decade, and possibly for some time after that."