Due to turbid water clarity, excess nutrients and historically heightened E. coli concentration, Storm Lake remains on an annual impaired waters list released this week.
The 113-page report, currently in its draft stage, was compiled by the Iowa Environmental Protection Commission and the Iowa Dept. of Natural Resources.
"Making the list does not necessarily mean the river or lake has a severe impairment, like a stream running with open sewage," Senior DNR Environmental Specialist John Olson explained. "Most of the time, making the list is more like an early warning system, indicating potential water quality programs exist or are developing."
Across the state, 482 bodies of water have a total of 656 impairments, ranging from fish kills to bacteria issues. Including Storm Lake, 87 Iowa lakes and reservoirs are listed with 241 impairments.
Out of all the lakes surveyed in the state, 34 percent have good water quality, while 58 percent are impaired and eight percent potentially impaired. For lakes, cloudy water, suspended sediment and high bacteria levels are the most common problems.
According to Olson, Storm Lake's turbidity, or murky water quality first caught the DNR's attention in 1998, and remains an ongoing problem.
"Although the lake data collected from 2006 to 2010 shows some slight improvement levels in water clarity at Storm Lake, the turbidity levels are elevated, relative to other Iowa lakes," Olson told the Pilot-Tribune. "The level of water clarity, as measured by Secchi depth, remains in the impairment range based on the trophic state index."
DNR Senior Environmental Specialist Julie Sievers said Storm Lake's water quality is still "far away" from reaching a goal set by the DNR in 2005. Until reaching the goal, the state's fourth-largest natural lake will remain on the list.
In an effort for continued improvement, dredging operations are expected to continue for another five years.
Based on past data, E. coli became a concern in 2010. For the 2012 report, research as far back as 2004 was considered.
"They are looking at data that is older and not current, because of the time length it takes to put the report together and compile them," DNR Senior Environmental Specialist Julie Sievers explained.
In 2012, E. coli levels were decreased by drought-like conditions.
"Generally, as in most lakes, those levels are elevated after rainfall," Sievers said. "We had very little rain this year, so levels are much lower."
Throughout the year, heavy rain or birds congregating near beaches can contribute to bacteria fluctuations in different areas of the lake.
"If we have rainfall, people should stay out of the water for 24 to 48 hours, but after good sunshine, the water should be fine," Sievers said, noting the City of Storm Lake is actively pursuing E. coli reduction strategies.
Although the report indicates the likelihood of contracting waterborne illness as "extremely rare," severely heightened bacteria levels can occasionally hamper recreational use of lakes.
In 2009, swimming was not advised for five out of seven consecutive summer weeks after fecal bacteria levels at a beach near Storm Lake's waterfront resort were five times the state-recognized limit.
However, Storm Lake's issues are currently listed as "low" priorities.
"In terms of water quality condition, 'impairment' is not a 'one size fits all' concept. The degree of water quality impairment ranges from slight to severe," the report states. "Many waters assessed as 'impaired' for aquatic life uses often continue to support a moderately healthy and diverse aquatic community."