The West Nishnabotna River Watershed in Southwest Iowa is a tributary of the Missouri River. The watershed includes 489,500 acres within the Southern Iowa Drift Plain Region, with its steeply rolling uplands and wide valleys. Scott Holmes Photo/Flickr Creative Commons
The West Nishnabotna River Watershed (WNRW) in Southwest Iowa is a tributary of the Missouri River. The watershed includes 489,500 acres within the Southern Iowa Drift Plain Region, with its steeply rolling uplands and wide valleys. This area consists of thick loess deposits with underlying glacial till and is highly erodible and susceptible to severe stream degradation. The river is used heavily for recreation and tourism, and it provides many historic and cultural resources, including the only state-designated water trail in Southwest Iowa. Currently, 80% of the watershed is cropland.
Channel straightening in the early 1900s affected about 90% of the lower 100 miles of the river. An estimated $1.1B in damage has accrued from damaged bridges, utility lines, culverts, farmalnds, and sediment deposition from post-channelization streambank erosion. Today, the West Nishnabotna River Water Trail is one of the most physically altered state water trails in Iowa, with 15-foot high banks and no riparian zone. In 2013, the Iowa Nutrient Reduction Strategy identified the West Nishnabotna River Watershed as a high priority area for implementing best management practices for reducing nitrogen and phosphorous loads.