There have been a number of E. coli outbreaks at Back Bone State Park in Delaware County.

The Iowa Department of Natural Resources took recent samples, which show bacteria has exceeded the limit in the water. So, the DNR issues an advisory against swimming at the park's beach.

If visitors chose to go in the water, the DNR says they should immediately shower, and more importantly, never drink the lake water.

The DNR says, high E. coli rates in this water can be a common occurrence in the summer, especially if there's heavy rains.

"We have a history of runoff because of the size of the watershed and the size of the lake. the lake is only an 80 acre with a huge watershed, you know you're obviously going to get some bacteria from the agricultural land," Park Manager Mary Shea said.

The DNR says if the region stays dry the bacteria will clear up. But there's no exact way to tell when that will happen.