Minnesota Water Resources Conference - Water Resources Center ...

BOOK OF ABSTRACTS
Tuesday, Monday, October 27 23
Concurrent Sessions I 10:00–11:30
Track B: Managing Water Quantity and Quality in the Minnesota River Basin
Rush River Hydrologic Study and Watershed Assessment Project
Bob Barth, Bonestroo, bob.barth@bonestroo.com; Emily Resseger, Bonestroo
Recently, there has been heightened interest in the hydrologic and water quality impacts of intensive
agricultural land use in the Minnesota River basin. Increased agricultural production is made possible by
draining wetlands and historic lakes. However, these drainage systems contribute to degraded water quality
and increased bank erosion in the Minnesota River and its tributaries. Specifically, increased hydrologic
variability leads to more flooding, causing bridge washouts, sedimentation, changes in stream alignment, and
greater nutrient transport.
As part of a larger Clean Water Partnership project, a hydrologic study of the approximately 400 square mile
Rush River watershed focused on surface and tile drainage processes to identify opportunities for volume
reduction. A detailed hydrologic and hydraulic XP-SWMM model of the Rush River watershed was calibrated to
monitored flow rates collected near the mouth of each of the Rush River’s four main tributaries and in the River
itself prior to joining the Minnesota River.
The model identified and assessed potential storage areas and their ability to reduce flow in the Rush River.
One of the most compelling findings of this study was how subsurface tile drainage affected the timing and
magnitude of outflow hydrographs. By characterizing the surface hydrograph separate from the hydrograph of
subsurface tile drainage, the total basin hydrograph closely matched the monitored flows. The study concluded
that a comprehensive program to restore key lakes and wetlands throughout the watershed is required in order
to provide adequate storage and reduce peak flows to more sustainable levels.
Evaluating Different Strategies for Reducing Nonpoint Source Pollution in Seven Mile Creek Watershed
Brent Dalzell, University of Minnesota, bdalzell@umn.edu; David Mulla, University of Minnesota
Water quality models are routinely applied to assess the feasibility of alternative management practices or
land use scenarios for the purpose of achieving improvements for stream water quality. One shortcoming of
this approach is that alternative scenarios are often applied to the watershed in a uniform manner and the
relative sensitivity of different portions of the landscape is not taken into consideration. In this study, we
evaluate different land cover and land management scenarios in Seven Mile Creek watershed, a predominatelyagricultural
watershed located in the Minnesota River Basin. A suite of alternative management scenarios was
developed based on historic land cover data (e.g., location of pre-settlement wetlands) as well as topographic
characteristics. Further, we assess how decisions about identifying sensitive landscape components are
influenced by input data by comparing results obtained from digital elevation models of varying resolution. The
performance (and shortcomings) of different approaches for designing alternative management scenarios will
be presented.
19 Minnesota Water Resources Conference, October 27–28, 2008