Graham Sustainability Institute

Informing Lake Erie Agriculture Nutrient Management via Scenario Evaluation

Lake Erie algal bloom, 2011. Photo by Peter Essick, National Geographic

Why this work?

Full Updated Report (PDF) SWAT FAQFact Sheet (PDF)Harmful algal blooms (HABs) have become common to the western basin of Lake Erie. The cyanobacteria Microcystis spp. produces toxins that pose serious threats to animal and human health, resulting in beach closures and impaired water supplies, and required the City of Toledo water system to issue a "Do not Drink" alert for several days in the summer of 2014. The main driver of Lake Erie HABs is high phosphorus loading from agricultural watersheds draining to the western basin, particularly the Maumee River watershed.

Through the 2012 Great Lakes Water Quality Agreement, the governments of the U.S. and Can­ada agreed to revise Lake Erie phosphorus loading targets with the goal of decreasing incidence and duration of HAB events below that representing a hazard to ecosystem and human health. Those target loads, adopted by the U.S. EPA and Environment Canada in February 2016, include a 40% reduction of the Maumee River loads from 2008 levels.

What are the options for meeting the target load reductions?

Because at least 85% of the phosphorus loads from the Maumee watershed come from agricultural lands, this research was designed to identify the types of agricultural best management practices and the level of implementation that may be required to meet phosphorus reduction targets for both total phosphorus (TP) and dissolved reactive phosphorus (DRP) from the Maumee River watershed, and to deliver this information to the Great Lakes policy and management community.

Multiple Model Approach

With support from the Fred A. and Barbara M. Erb Family Foundation and numerous partnering organizations, watershed modeling groups used a multiple model approach to explore and evaluate potential land management options for meeting phosphorus load reductions targets for the Maumee River watershed.

The multiple model approach is designed to raise confidence in model results. This project involved six modeling teams who had calibrated watershed models for the Maumee River watershed capable of including agricultural best management practices in various scenarios, five using the Soil Water Assessment Tool (SWAT), and one using the SPAtially Referenced Regressions On Watershed attributes (SPARROW) model. Using multiple models increases our ability to capture a range of potential outcomes, while also smoothing out extremes that may exist in individual models.  

For more information on SWAT modeling, see Frequently Asked Questions.

Key Findings

  • Some combinations of practices can achieve both TP and DRP targets.
  • However, widespread adoption (25-100%) of those practices is needed to meet phosphorus reduction targets.
  • Targeted placement of practices (e.g., to areas of greatest estimated phosphorus loss) is more effective than random placement

For More Information

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Project Contacts

Jennifer Read, Water Center Director, (734) 763-2642,
Don Scavia, Graham Sustainability Institute
Margaret Kalcic, Water Center
Rebecca Muenich, Water Center