Minnesota Water Resources Conference - Water Resources Center ...

Concurrent Sessions VI 3:00–4:30
Track A: TMDL
BOOK OF ABSTRACTS
Wednesday, Tuesday, October 24 28 23
Water Quality Data for Lake Nutrient TMDLs: How Much is Enough
Rebecca Kluckhohn, Wenck Associates, Inc., rkluckhohn@wenck.com; Merle Anderson, Clearwater River Watershed District;
Diane Spector, Wenck Associates, Inc.
Current approaches to setting lake nutrient TMDL’s involve expensive data collection modeling efforts.
This paper compares implementation plans developed for lakes using large and small data sets and asks
the question: How different is a $5,000 Implementation Plan from $50,000 plan Due to pressure from
lakeshore residents concerned over rapidly declining water quality in Cedar Lake, we used an Implementation
Strategy Ranking System (ISRS) in conjunction with a small but robust set of data and tools to draft an
implementation plan for the lake. The ISRS was used to understand the relative costs and uncertainty
associated with each implementation strategy. Additional data was collected to reduce the uncertainty and
refine the implementation plan; however the differences between the draft and final plans resulted mostly from
stakeholder input and logistical limitations, not from a reduction in uncertainties afforded by the additional
data. Lessons learned have implications for all TMDLs in Minnesota.
Integrating Geomorphologic Field Assessment and Watershed Modeling for Turbidity TMDL
Greg Johnson, Minnesota Pollution Control Agency, gregory.johnson@state.mn.us; Troy Naperala, URS Corporation; Karen
Evens, Minnesota Pollution Control Agency, Julianne Socha, USEPA
The Poplar River turbidity TMDL was developed using total suspended sediment (TSS) as a numeric target.
Sediment sources were quantified by analyzing water quality data, a physical channel assessment and computer
modeling. Results of the data analysis indicated that: 68% to 85% of the TSS was originating in the lower Poplar
River watershed; 73% of the turbidity exceedances occurred during high flow, and; 55% of the TSS reached the
stream during April and May.
The results of the physical channel assessment and WEPP computer modeling showed that:
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Near stream land slides contributed 428 to 1,024 tons/ year;
Gullies and ravines contribute 50 to 400 tons/ year;
Disturbed lands (ski runs, roads, trails) contributed 330 to 990 tons/ year;
Forest land contributed 140 to 421 tons/ year and;
Other sources (channel incision, golf courses, and developed areas) contributed 38 to 140 tons/ year.
Minnesota Water Resources Conference, October 27–28, 2008 76