"Algae prompt Des Moines to switch drinking-water rivers"

From the Des Moines Register:

Record levels of potentially toxic algae in the Raccoon River have once again forced the Des Moines Water Works to draw from the Des Moines River to keep drinking water free of poor tastes, bad smells and health risks.

Levels of blue-green algae — also known as cyanobacteria — for the past month have been higher than those of last year, when readings were the highest Water Works CEO Randy Beavers had seen in his nearly 30 years of service.

Samples collected from the Raccoon in recent weeks have frequently exceeded 20,000 cyanobacteria cells per milliliter of river water — well beyond levels that can easily be treated for use as drinking water. Tests from this week showed levels above 60,000 — the highest waterworks employees have ever measured in the Raccoon River.

In some cases, cyanobacteria can release a toxin that can sicken or even kill animals and humans.

"That's one of the reasons we go to the Des Moines River as another safety precaution should there be any unforeseen spikes in that toxin," Beavers said. "Fortunately, the toxin has been at very low concentrations."

Of further concern this year: Blue-green algae blooms have been more prevalent in the Des Moines River than in the past.

"It's problematic for us when we are, in essence, reduced to one river source," Beavers said. "Our current treatment system just has a very difficult time handling the really high counts" of cyanobacteria. "From an infrastructure standpoint, we feel water quality should be sufficient that we could draw water from either river."

...It would probably cost $1 million or more to upgrade treatment facilities to handle consistently elevated levels of cyanobacteria, Beavers said.

Instead, Beavers and others are hopeful improvements can be made throughout the 2.3-million-acre Raccoon River watershed to decrease the amount of nutrients such as nitrogen and phosphorus that feed the growth of algae blooms....