(March 24, 2004) - (Rogers-AP) -- Laboratory analysis shows water quality in the Illinois River is improving. The waterway is at the center of a dispute between Oklahoma and Arkansas. Oklahoma put in place water quality standards that forced Arkansas to make changes to reduce phosphorus discharges into waterways that flow into Oklahoma. Arkansas is still working through how to put all the changes in place. Marc Nelson, supervisor of the Arkansas Water Resource Centers, said yesterday that municipal water treatment plants are doing a better job of reducing phosphorus in treated water.