What’s in the flood waters?

SIOUX FALLS, S.D. (KELO) — The unknown could be lurking under the flood waters in South Dakota and Iowa.

“Whatever is out in the environment, within range of flood waters could potentially be in the water,” said Jay Gilbertson, the manager of the East Dakota Water Development District.

“A flood like we had, a localized flood, it’s going to pick up whatever it picks,” said David Kringen, the South Dakota State University Extension Water Resources Field specialist.

The National Weather Service said Tuesday it had a preliminary count of 19 sites where rivers had reached or had the potential to reach record crests. The Rock River in Iowa, the Big Sioux River in Iowa and South Dakota were among those 19 sites.

What’s in that flood water, “it could be a fence, it could be a tree or a building structure,” Kringen said. “You just don’t know.”

Kringen said the public needs to stay out of the water until it recedes.

The Rock River, Vermillion, James and Big Sioux traveled through and past farm fields and towns.

“Going through town, it could pick up parts of a house,” Gilbertson said. “If the John Deere mower in the garage was covered in three feet of water, whatever is on or in that mower is in the water.”

Yard or household chemicals can end up in flood waters. Levels of E coli and other bacteria can be carried from a farm or city. So can nitrates.

Some cities had to divert wastewater into rivers because the rain and flooding overloaded capacity or damaged plants. Vermillion had to discharge wastewater into the Vermillion River after several pumps failed. Sioux Falls had to discharge wastewater into the Big Sioux River.

The discharge increases the total level of suspended solids (TSS) in a river or lake and in the flood water ponding in a field, for example. TSS includes human matter, animal matter, algae and similar.

Flooding erodes banks and forces soil from fields which can also add to the TSS in flood waters.

Before the James, Vermillion, Rock, via the Big Sioux River, and the Big Sioux enter the Missouri River, they will leave some debris behind.

A city park like Yankton Trail in Sioux Falls could be flood dumping ground of sorts, Gilbertson said. Mud and other debris could be left behind when flood waters recede.

Some of that debris can be bacteria which has forced the state to close at least three swimming beaches as of Wednesday.

The state Game Fish and Parks closed the swimming beach at Lake Alvin in Lincoln County and swimming beaches Gavins and Midway at Lewis and Clark Recreation Area because of unhealthy levels of bacteria in the water attributed to runoff and flooding.

Some of what gets picked up in the flood, “might go to the Missouri, it might go to the Mississippi or it might go to the Gulf of Mexico,” Kringen said.

Both Kringen and Gilbertson said heavier debris may get dropped as waters recede.

The flood itself may change the chemical makeup of a lake and the result could be more algae, Kringen said.

But, the shoreline could be more vulnerable if the wind causes waves in the high water, he said.

Any change in the lake’s chemical makeup would not be permanent, Gilbertson said.

The flood waters could, however, make a more long-lasting change in rivers, he said.

Flood waters can also fill a hole in a river if it dumps sediment in the hole but then, it’s likely another hole has been created in another part of the river, Gilbertson said.

Rivers have natural bends as they travel.

“Water takes the path of least resistance,” Gilbertson said. “If it elevates to 10 feet down to five feet and it can do that in 20 yards across a field instead of a 1/2 mile… You could see a change in the river channel.”

The extent of what the flood waters may have carried won’t be known for a while.

Kringen said property owners who have wells that got covered in flood water need to have them tested for bacteria and other materials.

“We don’t know what’s in the flood water, stay out until things go down,” Kringen said.

Gilbertson said the public should stay out of lakes and rivers that have been flooded for several days at least, even if water appears to have receded.

Just how deep the water is and what may be in it, can still be unknown, he said.

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