There are early signs that Lawrence officials once again will spend the summer fighting an organic battle to prevent the city’s drinking water from having taste and odor issues.

But this year, water plant operators may do their fighting on a different front.

Water plant operators are alerting city officials that elevated levels of organic materials are showing up at the city’s Kaw Water Treatment Plant. Last year, city officials experienced taste and odor issues primarily at the city’s Clinton Lake Water Treatment Plant.

“If this drought continues, we probably would anticipate a pretty active year on the taste and odor front again,” said Dave Wagner, the city’s director of utilities.

Activity levels already are pretty high, Wagner said. The city’s water treatment plant along the Kansas River is picking up increased amounts of geosmin in the raw water supply out of the river. Geosmin is a byproduct of dead algae. It isn’t harmful to human health, but at high enough levels it can create a musty taste and odor in treated water.

So far, Wagner said the city’s treatment process has been successful in reducing the geosmin levels to the point that ordinary consumers aren’t noticing any taste or odor issues. But that treatment has come at a cost. The city currently is using two to three times the amount of carbon in its treatment process than is normal for this time of the year.

The drought is a likely reason the Kansas River is experiencing higher geosmin levels than normal, where in the past reservoirs have experienced more of the issues. Wagner said almost all of the water in the Kansas River is being supplied by upstream reservoirs instead of through runoff after rains.

“We are talking about very, very low river flows,” Wagner said. “They are lower than anything I can remember.”

Wagner estimated that river flows currently are less than 800 cubic feet per second. A more typical number is about 6,000 to 7,000 cubic feet per second. Without the upstream reservoirs — such as Tuttle Creek and Milford reservoirs — Wagner estimates the river’s flow would be less than 300 cubic feet per second.

But the drought may not be the only factor playing into the higher levels of geosmin in the river. Wagner said it is possible renovations to the Bowersock Dam, just downstream from the water plant, have played a role. The renovations have included a new rubber bladder that increases the height of the dam, which in turn increases the depth of the mill pond in front of the city’s water plant by a little more than a foot.

The increased depth has had benefits to the city, including allowing for easier pumping by the city and decreased turbidity in the water. But the deeper mill pond also allows water to sit longer in the river, providing more time for organisms to grow, Wagner said.

“We don’t know how much of an impact that is having,” Wagner said. “But the increased depth does let it brew in there a little longer.”

Wagner said it is tough to predict how much more carbon the city may need to use this year to combat the geosmin and other taste and odor causing compounds. But Wagner said increased carbon usage does have the potential to impact his department’s budget. Last year, the city spent about $280,000 on carbon for the city’s two water treatment plants.

Concerns about taste and odor issues have caused city commissioners to consider raising rates to pay for more advanced treatment options at the two plants. The city’s latest water rate increase does include funding for a study to examine the feasibility of alternative treatment options. That study should be completed this year.

The city has estimated a new treatment system may require about $19 million in improvements at the city’s two treatment plants.