New Illinois River Report Shows Higher Phosphorus Levels

Tue, Jul 29, 2003

Scientists Warn That Storm Samples Skew Data Comparison

By Scott F. Davis

The Morning News/NWAonline.net

FAYETTEVILLE -- The latest water quality report on the Illinois River shows phosphorus levels increasing from 1997 to 2001, but part of this increase is because storm data was not available before July 1999.

The U.S. Geological Survey report -- funded in part by the Oklahoma Scenic Rivers Commission and the Oklahoma Water Resources Board -- shows current levels well above the proposed new Oklahoma phosphorus standard.

The report also shows that 60 percent to 90 percent of the phosphorus in the river is transported during rainfall. This represents "a combination of runoff and resuspension of phosphorus" from the streambed sediments, explained Kim Winton, USGS district chief in Oklahoma.

The study does not determine how much of the total phosphorus load measured is caused by runoff from agricultural or urban sites or from wastewater-treatment plant discharges, she said Monday.

The report examines five sites on the Illinois River or its tributaries in Oklahoma: the Illinois River near Watts, Okla., at Chewey, Okla., near Tahlequah, Okla., Flint Creek near Kansas, Okla., and the Barren Fork Creek at Eldon, Okla.

The mean levels of phosphorus increased by almost 100 percent at the Kansas, Chewey and Tahlequah stations and increased by more than 400 percent at the Eldon site, the report shows.

The three periods analyzed in the report combine data for three consecutive years, such as 1997 through 1999, 1998 through 2000 and 1999 through 2001.

The biggest reason for this increase could be a change in the methodology, because samples from storms were not available before July 1999, scientists explained.

USGS scientists cautioned that comparing these figures from different periods may be misleading, considering that "three different models were used from three different data sets from different sampling schemes."

"This is a very limited data set ... So it's difficult to take 'trend' out of data that are collected differently," Winton said.

She also noted that current budget constraints prevent preparation of new reports from more recent data. An analysis of other data on bacteria, turbidity, alkalinity and temperature and how these relate to phosphorus would also be helpful in developing a management strategy, she explained.

This new report comes as Arkansas and Oklahoma officials are tying to reach agreement on how to implement water quality standards adopted by Oklahoma last year.

The standards -- currently under review for approval by the U.S. Environmental Protection Agency -- include a numerical limit on phosphorus of 0.037 parts per million.

The three sites with the highest phosphorus levels -- Kansas, Watts, Chewey -- are 8 to 10 times higher than Oklahoma's new standard.

In the report, the Eldon site on the Barren Fork showed an increase from 0.045 to 0.19 parts per million.

Oklahoma officials have used the earlier Barren Fork numbers as evidence that its standards can be achieved.

Phosphorus levels measured during base flow conditions were much lower and the increases less significant. At base flow, the Eldon site increased 50 percent from 0.02 ppm during 1997 through 1999 to 0.03 ppm during 1999 through 2001. This is the only site that meets the Oklahoma standard, if measured at base flow.

During these same periods, base flow levels -- in parts per million -- increased by:

• 50 percent from 0.06 to 0.09 near Tahlequah.

• 13 percent from 0.15 to 0.17 near Kansas.

• 50 percent from 0.12 to 0.18 near Chewey.

• 41 percent from 0.17 to 0.26 near Watts.

The report noted that the base flow levels are higher near Watts than the other sites, because upstream wastewater treatment plants from Springdale, Rogers, Fayetteville and Prairie Grove discharge into the river's tributaries.

The Kansas site is affected by Siloam Springs' upstream plant.

Arkansas officials, including Gov. Mike Huckabee, have called the 0.037 limit unrealistic and unattainable.

Phosphorus at high levels promotes excessive algae growth, which can cause water to turn green, lower dissolved oxygen levels and lead to taste and odor problems in treated water drawn from reservoirs.

Officials of both states and the EPA -- after meeting in the EPA Region 6 office in Dallas in late June -- said Arkansas and Oklahoma are close to reaching an agreement on a plan to implement the new phosphorus standards.