Introductory Speakers: Patrick Belmont & Carrie Jennings

Description: Currently, our understanding of integrated watershed sediment dynamics in low-relief landscapes is insufficient for proper development of widely-applicable, predictive models of sediment sources, transport and storage. This insufficiency limits our ability to deconvolve anthropogenic versus natural drivers of landscape change and limits our ability to develop reasonable management goals in these economically important landscapes.  The presenters will describe on-going work to create a sediment budget for the Le Sueur River, a tributary to the Minnesota River that delivers one-third of the sediment load from a mere 7% of land area in the Middle Minnesota River watershed.

The Le Sueur River flows into the incised Minnesota River valley. The Minnesota River incised 11,500 years ago as a result of the draining of glacial Lake Agassiz, initiating a major knickpoint that is migrating through the Le Sueur River network into low-gradient uplands that have recently been converted from naturally occurring long-grass prairie to 90% agriculture. Although evidence suggests that pre-settlement sediment loads in the Le Sueur were high, sedimentation rates derived from cores in downstream Lake Pepin indicate an order of magnitude increase in sediment delivery since 1830.  Primary sediment sources include uplands, ravines, high bluffs, and streambanks. Our sediment budget is based on several parallel approaches: 1) sediment provenance determination using cosmogenic nuclides and other geochemical tracers; 2) repeat surveys of bluffs and ravines, flood plains, and channel geometry; 3) quantification of rates of meander migration and bluff retreat from historic and modern aerial photography; 4) measurement of modern sediment fluxes from sediment gaging data; and 5) surficial mapping and stratigraphy.

Presenter Bios:
Patrick Belmont is a postdoctoral research associate at the University of Minnesota working with the National Center for Earth-surface Dynamics. His research is dedicated to understanding how landscapes change over long and short timescales and how living organisms influence, and are influenced by, those changes.He is currently working to develop an integrated sediment budget on the Le Sueur River.

Carrie Jennings is a Senior Scientist at the Minnesota Geological Survey and Adjunct Faculty in the Department of Geology and Geophysics.  She has investigated the origin of the glacial landscape of Minnesota through mapping and comparative research of modern glaciers. 

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SUMMARY

The second Partnership for River Restoration and Science in the Upper Midwest (PRRSUM) monthly forum was held on March 11, 2008, at the St. Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN.  Nearly 30 people attended in person, while another 10 or more joined the forum online.  Web viewers watched the conversation live online and typed questions or comments for the moderator to address to the live forum.  Each forum will also be archived online for later viewing.  We plan to continue this option for at least the rest of the spring.  Please contact Jeff or Anne if you have feedback on the webstreaming process.

The forum topic was sediment dynamics in agricultural watersheds.  Patrick Belmont, National Center for Earth-surface Dynamics, UMN and Carrie Jennings, Minnesota Geological Survey, described their ongoing work to learn more about sediment sources in the Le Sueur River basin, as part of the larger effort to determine a sediment total maximum daily load (TMDL) for the Minnesota River. The 30 minute talk was followed by questions on the talk and a discussion on the forum topic.

Summary of major ideas raised during the discussion:

• The turbidity TMDL in the Minnesota River basin is scheduled to be completed in December 2008, with related HSP modelling work to be done by February 2009.
• Since both the Mississippi River and Lake Superior have experienced post glacial base-level fall, any tributary in either system could have similar issues to those of the Le Sueur and its tributaries. 
• Elm Creek has also had high levels of suspended sediment.  Bank incision is not responsible; road crossings may be the culprit.
• The volume of water not the shape of the hydrograph is crucial to determining sediment erosion. Increases in volume are attributed to reduction in infiltration.
• The spring thaw (high discharge before crops are in place) is important to annual agricultural sediment budget.  Perennial cover may be able to reduce sediment loading to ditches, but it has little harvest potential in the absence of biotechnology.  Farmers are increasingly tilling crop residue under to increase soil cohesion.

Pop-ups and Announcements:

1. Some attendees were in the Twin Cities to visit the state legislature due to proposed legislation proposed TMDL related taxation in the Minnesota River Valley. A meeting will be held in Gaylord on March 17, 2008, to further discuss this issue. 
2. Researchers at St. Anthony Falls Laboratory will begin working in the new Outdoor StreamLab this summer.  One of the first projects will consider the effect of different types of turbidity on aquatic health, with the goal of determining what metric is most appropriate to characterize sediment pollution.  More information is available at www.safl.umn.edu/OSL or by contacting Anne Lightbody at annel@umn.edu.

3. Is there a need for a Upper Midwest River Restoration Conference. Regional conferences have been successful elsewhere in the U.S. (e.g. River Restoration Northwest (http://www.rrnw.org).  There is currently no conference within the Upper Midwest that addresses river restoration.  One possibility would be to hold a one-day meeting (beginning in 2009) immediately following the Water Resources conference that is held in the Twin Cities each October. PRRSUM could lead organizing this conference. Feedback is welcome on this idea.

The next PRSSUM meeting will be held April 8^th.  The topic will be the restoration of incising streams.  Jeff Hastings of Trout Unlimited will give an introductory presentation on the restoration of incising streams within the Driftless Area.