Timeline Impaired for turbidity on Minnesota’s list of impaired waters (2004) MPCA must complete a study to determine the total maximum daily load (TMDL) TMDL study was started in 2006, but was not finished at the planned date (2008) The MPCA requested that the U of M team continue the work and to estimate contributions of erosion sources Targeted completion of the Draft TMDL is 2011

Background High turbidity threatening trout stream and health of Lake Superior Turbidity is caused by suspended silt/clay Poplar River is considered a nonpoint source (both natural and anthropogenic sources of pollution) Significant streambank and bluff erosion observed; suspected as primary sources Some measures have been taken to reduce the sediment load in the river (Mega Slump)

Specific Water Quality Problems When comparing upstream to river mouth loading rates: Phosphorus increased by 2X Total suspended solids (TSS) by 6X Mercury levels exceeded the state standard Mercury and TSS levels were strongly correlated Reducing sediment loss rates in the lower Poplar River will be beneficial for reduction of total mercury quantities into Lake Superior. “…juvenile [trout] population has declined in the Poplar since 1989.” Water quality sampling was conducted according to approved MPCA quality assurance procedures (MPCA, 2000)

Comparison of Turbidity at different sites in the Poplar River

Upstream and downstream sites on the Poplar River, July 30, 2001 after a large rainfall (approximately 3 mi apart) Photo credits: MNPCA 2002

114 square miles of drainage area Lots of upland lakes and wetlands Soils: red lake clay and Superior lobe till 25.5 miles of river Has the highest percentage of urban land use of the monitored north shore trout streams (3.5%, mostly in the lower river area) Stream bed is composed mostly of boulders and cobbles

Objectives Acquire archived data, geomorphic data of the river and watershed, and other watershed data Apply sedimentation generation and sediment transport models to assess potential sediment sources and their impact on loading and transport within the river Evaluate and asses the sources of sediment entering and being transported within the Poplar River to Lake Superior

Current Activity Acquiring and processing channel morphology data for critical sections of the lower Poplar River Collected by the Cook County SWCD, MPCA, and MNDNR Identify a reference watershed and stream to compare sediment generation Modeling work plans for future studies will be formulated

Future Activity Watershed modeling will be done to: Better delineate the upland runoff erosion sources Determine different sources’ contribution to sediment load Field data will be used in three models to provide estimates of erosion generated from the streambanks and bluffs Development of a method to monitor BMP effectiveness Test this method on the Mega Slump U of M will assist the Cook County SWCD with incorporating the results of these tasks into a

Task 1- Provide Monthly Reports and Feedback to the MPCA and Cook County SWCD Results of project activities will be presented Alternative directions will be considered If any changes are made, they will be documented

Task 2- Identify a Reference Watershed and Stream Necessary to understand what an undisturbed stream will do in terms of: Sediment production Bank erosion Stream flow Etc. Stream should have similar characteristics to the Poplar River Majority of water from upland lakes and wetlands Soil types- red lake clay and Superior lobe Drainage area Low amounts of sand, silt, and clay in stream bottom; mainly boulders with cobbles Others- shape, topography, geology, channel morphological and vegetation characteristics

Task 3- Work with Stakeholders to Identify Modeling Needs and to Develop a Modeling Approach Additional watershed modeling to: Delineate upland runoff erosion sources Determine the upland erosion sources’ contribution to sediment load in the river Some has been done with limited detail of vegetation and land use types Stakeholders and U of M team will meet to: Identify the categories that will be used Discuss input variables and assumptions to be incorporated Identify the location of categories in the watershed

Task 4- Conduct a Sediment Assessment for Poplar River and Reference Stream Field data collection Collect from both reference stream and Poplar river Focus on: Morphological characteristics Hydraulic characteristics Others: Cross-section geometry visual observations of streambank soils, vegetation, and aquatic life habitat in-channel sediment characteristics shear strength and cohesive strength of bank materials longitudinal profiles

Task 4- Conduct a Sediment Assessment for Poplar River and Reference Stream, cont. Selection of storm events for modeling Identify storms Use historical streamflow and precipitation data for the Poplar River 63-year streamflow record (USGS) Additional flow records for more recent years (MPCA) Use rainfall intensity records (if they exist) from nearby station to relate flows to rainfall Quantify sediment load generated using the sediment concentration and flow records

Task 5- Preparation of Final Report Draft a final report on the work conducted Submit to the MPCA by September 30 th, 2009 Incorporate comments from the MPCA into the draft by October 30 th, 2009

References Poplar River, MN (Cook County), 2006 Automated, in situ, Water Quality Data: Preliminary Analysis