Concentrations of the nutrients nitrogen and phosphorus have decreased at several locations in two creeks that flow into Lake Eucha and Spavinaw Lake, near the City of Tulsa, Okla., according to a new U.S. Geological Survey report.
The City of Tulsa uses water from Lake Eucha and Spavinaw Lake for public water supply. From 1998-2005 the City has invested in eliminating taste and odor problems in the drinking water, which can be attributed to high levels of nutrients causing algal biomass in the water.
"It is a great service to communities when USGS monitoring of water quality demonstrates whether changes in management practices are having any impact on nitrogen and phosphorous levels in public water supplies," said USGS Director Marcia McNutt. "And it is a cause for celebration when that monitoring confirms that indeed those actions are having the intended beneficial effect."
Concentrations of nitrogen and phosphorus measured in 2010 were less than those typically recorded in from 2002–2009. USGS scientists tested for nitrogen, phosphorus, and suspended sediment at five streamflow-gaging stations in the Spavinaw and Beaty Creek basins in the Eucha-Spavinaw basin of northwestern Arkansas and northeastern Oklahoma. The report, written in cooperation with the City of Tulsa, is available online.
Estimated amounts of nitrogen and phosphorus delivered to Lake Eucha from the Spavinaw and Beaty Creek basins during 2002–2010 were 2.5 to 7.8 percent less, respectively, than the amounts discharged from 2002–2009.
Trend analyses of water-quality data indicated no significant downward trends in nitrogen-compound concentrations, but that there were significant downward trends in phosphorus and suspended-sediment concentrations at several sites on streams draining to Lake Eucha.
Possible causes for downward trends in phosphorus concentrations include decreases in phosphorus discharges from a wastewater-treatment plant upstream from the Spavinaw Creek near Cherokee City, Okla., and the effects of best management practices in the basin.