TimelineImpaired 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

BackgroundHigh 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

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

ObjectivesAcquire 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 ActivityAcquiring and processing channel morphology data for critical sections of the lower Poplar RiverCollected 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 ActivityWatershed 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 effectivenessTest 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 SWCDResults 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 StreamNecessary to understand what an undisturbed stream will do in terms of:Sediment productionBank erosionStream flowEtc.

Stream should have similar characteristics to the Poplar RiverMajority of water from upland lakes and wetlandsSoil types- red lake clay and Superior lobeDrainage areaLow 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 ApproachAdditional watershed modeling to:

Delineate upland runoff erosion sourcesDetermine 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 usedDiscuss 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 StreamField 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 stormsUse 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 ReportDraft a final report on the work conducted

Submit to the MPCA by September 30th, 2009

Incorporate comments from the MPCA into the draft by October 30th, 2009

Referenceshttp://www.lakesuperiorstreams.orghttp://www.pca.state.mn.ushttp://www.epa.govPoplar River, MN (Cook County), 2006 Automated, in situ, Water Quality Data: Preliminary Analysis