Water Quality Data for Lake Nutrient TMDLs: How Much Is Enough?

In the land of 10,000 lakes, setting lake nutrient Total Maximum Daily Loads (TMDLs) is a big job. Over 300 nutrient impairments have been identified with only 10–20% of Minnesota's lakes assessed. 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 can be used in implementing lake nutrient TMDLs for less.