(Radio Iowa) – The state Environmental Protect Commission has approved the use of federal funding to continue support of the Lake Rathbun watershed protection program in southern Iowa. Ginger Murphy from the D-N-R’s Water Quality Bureau oversees the project to improve aquatic habitat, and to reduce excess nutrient runoff. “It’s Iowa’s second largest lake and the 11th most visited in recent statistics. It is actually a reservoir formed by the Chariton River. And it continues 142 river miles downstream into the Missouri River,” she says. The lake helps with flood control and as the source of drinking water for 18 counties in Iowa and Missouri. The Rathbun Land and Water Alliance was created as a non profit organization in 1996 to provide the foundation for partnerships and cooperative management of the reservoir.

“The Alliance meets quarterly to update and collaborate with stakeholders and partners on the goals and progress of their watershed efforts, and the alliance has been implementing watershed management plans since 2004,” Murphy says. “The plans are updated to reflect changing land use, changing technology and practices, water quality monitoring and research, and improved soil loss models.” She says an E-P-A Clean Water Grant helps fund the watershed practices designed to improve the lake. “An emphasis on structural best management practices has been most effective in the Rathbun watershed, so they’re installing practices based on N-R-C-S standards that have maintenance requirements anywhere from ten to 35 years,” she says.

Murphy says there’s progress as landowner participation rates and sediment and phosphorus load reductions are encouraging. But she says in the past 20 year estimates show watershed cropland has increased from about 30 percent use to nearly 50 percent, which can mean highly erodible lands used for pastures may have been converted to row crops. Murphy says tests are done with a disc that’s dropped into the water to see how clear it is, with the goal of seeing it one meter down. They have 2024 results and will soon review 2025 data. “None of the sites, this would be the main basin and then some of the arms of the lake that have different tributaries feeding them, none of those sites met the one meter goal. We expect the 2025 data will probably be similar. This is just a trend with high turbidity in Rathbun Lake right now,” Murphy says.

She says they’ll look at that 2025 data at the Alliance’s spring meeting as they talk about moving ahead with the latest plan.