An emerging Best Management Practice for nutrient load reduction and habitat restoration
What is an oxbow lake?
Oxbows are floodplain wetlands that form when a stream or river cuts a straighter path through a loop of its natural meander. This can be a natural process when streams migrate through the floodplain, or human-caused if a stream is channelized. Often, the water in these lakes will dry up over time, leaving a depression in the land. Watch this video for more explanation: https://www.youtube.com/watch?v=4qKS_Nk7UmY.
Oxbows tend to disappear as they gradually fill with sediment and organic material from surrounding land. To restore them requires removing fill material that has accumulated over time.
Where are there former oxbows in Scott County?
Scott County’s rivers and streams have changed their courses hundreds of times over the decades, leaving scars in the landscape that indicate where former oxbow lakes once stood. Click this map to search for former oxbow locations and locations of abandoned stream channels in Scott County.
What benefits do oxbow restorations offer?
A two-year study in Iowa by Schilling et al., 2019, found that restoring former oxbow lakes can potentially reduce export of nitrate-nitrogen (nitrate) from agricultural land as well as provide important habitat for many species. Nutrient export from the agricultural US Midwest influences streams and rivers and contributes to the development of the “dead zone” in the Gulf of Mexico, killing wildlife and plant life that live near the mouth of the Mississippi.
The study found that oxbow restoration projects demonstrated a 45% reduction in nitrate export of water entering oxbows from subsurface tiles, compared with water discharged to the adjacent stream without passing through the oxbow. The study concluded that oxbow restorations are a promising new best management practice for reducing nitrate export from agricultural lands. Restoring oxbows is as effective as several other nutrient reduction practices, is relatively inexpensive and low maintenance, can last for decades if not centuries, remove little or no land from agricultural production, and provide significant ecosystem services. They also provide much needed habitat for wildlife in areas in which the land has been largely altered for agricultural purposes.
Oxbow restorations that intercept tile drainage before entry to streams are now recognized as an official nutrient reduction practice by the Iowa Nutrient Research Center. This will potentially open the door to funding assistance from multiple sources (more information below).
Is there funding assistance available for an oxbow lake restoration project?
Yes! According to Schilling et al. (2019), the cost of an oxbow restoration is similar to other edge-of-field BMPs like bioreactors (average cost of $10,000).
The organizations below have previously funded oxbow lake restoration projects. Please visit each organization’s web page for more information on funding eligibility, or contact Partners of Scott County Watersheds at [email protected] for additional assistance to find out if your project qualifies for funding.
Do you have an interest in restoring a former oxbow on your property?
Contact [email protected] and Partners of Scott County Watersheds may be able to provide technical assistance for your project!
The Nature Conservancy also has a great toolkit for oxbow restoration. View the digital toolkit here.