FAYETTEVILLE — Sediment from Lake Frances south of Siloam Springs could cause phosphorus levels to stay high for years even if major steps are taken to reduce phosphorus in the Illinois River watershed, a U.S. Department of Agriculture researcher said Wednesday.
Brian Haggard, a hydrologist with the Agriculture Department, shared his findings with attendees of the Arkansas Water Resources Conference, which met Tuesday and Wednesday.
Various Northwest Arkansas entities are trying to reduce phosphorus in streams flowing into Oklahoma, including the Illinois, because of Oklahoma’s 2002 passage of a numeric limit for phosphorus in its streams. Oklahoma officials think ecology of the state’s streams will improve if phosphorus can be reduced to 0.037 milligrams per liter of water.
Northwest Arkansas cities such as Rogers and Springdale have taken steps to reduce phosphorus by improving discharges from sewer plants. Arkansas also has passed laws regarding the uses of poultry litter, which contains phosphorus, in "nutrient sensitive" watersheds, such as the Illinois.
The Illinois River crosses from Arkansas into Oklahoma just before reaching Lake Frances. Phosphorus in the lake could inhibit efforts to reduce it, Haggard said.
"Based on the limited data, [the lake] could maintain above 0.037 for a long time," Haggard said.
Water sampling discussed at an Arkansas-Oklahoma Arkansas River Compact Commission meeting in 2002 showed the two states had far different findings regarding phosphorus in the Illinois River.
Arkansas officials said phosphorus levels were improving at a sampling point at the Arkansas 59 bridge just before the Illinois River flows into Lake Frances.
At Oklahoma sampling points downstream from Lake Frances, the levels were higher.
That’s why Haggard started evaluating the lake, which sits midway between the sampling sites, as a possible culprit.
The Lake Frances dam, built in 1931, was severely damaged by flooding on May 4, 1990. That lowered the lake’s depth, and it remains a fraction of its former size.
Ed Fite, director of the Oklahoma Scenic Rivers Commission, said Lake Frances is now 48 acres, so small that it doesn’t even warrant listing on the state’s water atlas.
"It’s not right to call it a lake anymore," Fite said.
Samples Haggard collected last summer showed the bottom mud was rich in phosphorus. That helped explain the difference between the phosphorus samples taken by the two states, he said.
Derek Smithee, water-quality chief for the Oklahoma Water Resources Board, said Lake Frances may help explain the testing differences.
"It makes sense that Lake Frances is a factor," Smithee said. "The question that begs to be asked is, ‘How big a factor is it?’ "
That answer may come from future research headed by the two-state compact commission, Smithee said. The commission plans to request $9.3 million in federal money to monitor streams in Arkansas and Oklahoma, including the Illinois River, which drains large sections of Benton and Washington counties.
Within the $9.3 million request is $1.25 million that’s being sought for specialized studies to look more closely at Lake Frances and what can be done to reduce the impact of the phosphorus found in its sediment, Smithee said.