Univ. of minnesota student brian bohman tracks increased sedimentation in minnesota river

by Brian Bohman for Minnesota Water Resources Center

A picture of Brian Bohman measuring soil moisture content with a neutron probe in order to improve irrigation management.
Brian Bohman measures soil moisture content with a neutron probe in order to improve irrigation management.
(Photo courtesy of Minnesota Water Resources Center).

Research on non-point source water quality issues is not just confined to the academic setting for members of the Minnesota Water Resources Science (WRS) program. Carrie Jennings, Research and Policy Director at Freshwater Society and WRS Adjunct Assistant Professor in the Department of Earth Sciences, and Brian Bohman, WRS M.S. student and Research and Policy Intern at Freshwater Society, are working together to cross traditional disciplinary and academic boundaries. Through collaboration at Freshwater Society, the two are applying recent research findings to help the Lower Minnesota River Watershed District (LMRWD) identify the sources of and solutions to their problem of excess in-channel sedimentation.

For Bohman and Jennings, the goal of this project was to synthesize existing research in order to communicate the magnitude of change with stakeholders throughout the Minnesota River Basin. Based on USGS streamflow and sediment gauging as well as historical sediment cores, they estimate that there is 1/2-inch of sandy sediment deposited in the Minnesota River channel between Jordan and Ft. Snelling each year, representing a six-fold increase in rate relative to the rate of sedimentation prior to European settlement. In-channel sedimentation impacts commercial river navigation and requires additional dredging by the US Army Corps of Engineers at an increased cost to LMRWD and tax payers. Potential strategies to restore the hydrology and sedimentation regime of this stream reach include installing perennial cover and on-land water storage throughout the MN River Basin to increase evaporation and transpiration, reduce peak flows and total water delivery.

Bohman has been leveraging the skills he has developed as a WRS student to help advance the Freshwater Society’s mission of keeping lakes and streams healthy and protecting drinking water through efforts of community education, science-centered policy, and collaborative action to move conservation efforts forward. Although not directly related to his graduate research project, exposure to this work while a student is valuable because it provides experience on how to bringing the scientific research and ideas into action. As a M.S. student in WRS graduate program, Bohman works with David Mulla (WRS faculty, SWC) and Carl Rosen (SWC) on a project focusing on managing irrigation and nitrogen inputs for potato production with the goal to reduce nitrate leaching into groundwater supply.

The results of this collaboration include a report published by the Freshwater Society and an article by Jennings in Open Rivers, an online journal published at the University of Minnesota. Links to both articles can be found on the website for Freshwater Society: www.freshwater.org