Lake Erie’s harmful algal bloom problem is not abstract. It is not something that happens far away from the fields, rivers, drainage ditches, and communities that shape the health of the lake.
It begins upstream.
One of the biggest drivers of harmful algal blooms in Lake Erie is excess phosphorus, especially phosphorus that leaves farm fields and moves through drainage systems into rivers and streams that eventually flow into the lake. Once that phosphorus reaches the western basin, it can help fuel the algal blooms that threaten drinking water, hurt wildlife, damage recreation, and put shoreline communities at risk.
For years, the Lake Erie Foundation has pushed for practical, science-based solutions that reduce phosphorus before it reaches the water. The Phosphorus Runoff and P-Filter Project is one of the clearest examples of that work.
This grant-funded project, located in northwest Ohio in the Maumee River Watershed near Defiance, Ohio, is focused on a direct and urgent goal: identify high-phosphorus fields and install targeted filter systems that remove phosphorus from runoff before it can make its way downstream toward Lake Erie.
This is not just education. It is not just advocacy.
It is implementation.
Why Phosphorus Runoff Matters
Phosphorus is a nutrient that helps crops grow. But when too much phosphorus leaves farm fields and enters waterways, it becomes a serious water quality problem.
In Lake Erie, excess phosphorus is a major contributor to harmful algal blooms. These blooms can produce toxins, reduce water quality, harm fish and wildlife, close beaches, affect boating and tourism, and create major concerns for communities that depend on the lake.
The Maumee River Watershed is especially important because it is one of the largest sources of phosphorus entering Lake Erie’s western basin. If we want to reduce harmful algal blooms in Lake Erie, we have to reduce the amount of phosphorus leaving the land and entering the Maumee River system.
But not every field contributes equally.
Some fields, often called High P Fields or Legacy Fields, have built up high levels of phosphorus over many years. Even when better nutrient practices are used today, these legacy fields can continue releasing phosphorus through runoff and tile drainage.
That makes them a high-priority target.
The solution is not to treat every acre the same. The solution is to find the fields that are contributing the most phosphorus and focus resources where they can make the biggest difference.
That is the strategy behind the Phosphorus Runoff and P-Filter Project.
Watch: The P-Filter Video
Finding the Right Field
Before anything could be installed, the right site had to be identified.
The Lake Erie Foundation worked with agricultural and engineering partners to survey and evaluate potential fields in northwest Ohio. These efforts focused on identifying High P Fields, or Legacy Fields, where phosphorus runoff was likely to be a significant concern and where a filtration system could intercept runoff before it moved farther downstream.
The selected site is located near Defiance, Ohio, in the Maumee River Watershed. Out of respect for the landowner’s privacy, the specific farm location is not being publicly shared.
This field was not chosen at random. It was selected because it represented the kind of high-impact location where a phosphorus filter could make a measurable difference.
That matters.
Too often, conservation efforts are discussed in broad terms. But Lake Erie needs targeted action. If a smaller number of high-phosphorus fields are responsible for a larger share of phosphorus runoff, then identifying and treating those fields is one of the most practical ways to reduce the load entering the watershed.
The P-Filter Project is built around that idea.
Find the right fields. Install the right systems. Measure the results. Use the data to guide future action.
How the P-Filters Work
The P-filters are designed to treat farm runoff before it reaches the waterways that feed Lake Erie.
As water drains from the field, it is directed through a filter system. Inside the system, the water passes through filter media designed to capture phosphorus, including dissolved reactive phosphorus, which is one of the forms most closely connected to harmful algal bloom growth.
The goal is simple: allow the field to continue draining while removing phosphorus from the water before it leaves the site.
Instead of waiting until phosphorus is already in the river, the P-filter captures it closer to the source.
That is what makes this project so important. It is a field-level solution to a lake-wide problem.
The project currently includes five filters. These filters are being monitored so LEF and its partners can better understand how much phosphorus they remove over time and how they perform under real-world conditions.
From Planning to Installation
The project moved from planning to installation between late 2024 and fall 2025.
During that time, the Lake Erie Foundation and its partners worked through the process of evaluating the site, coordinating with the private landowner, developing the filter approach, and installing the systems.
Flint Run Engineering served as the engineering partner for the project, helping bring the technical and field-level pieces together.
Because the project was grant-funded, it also shows how conservation work can move from idea to action when funding, technical expertise, landowner cooperation, and nonprofit leadership come together around a shared goal.
This kind of project requires more than concern for Lake Erie. It requires planning, engineering, trust, field access, installation work, and long-term monitoring.
That combination is exactly what makes the Phosphorus Runoff and P-Filter Project valuable.
It is not a talking point. It is a working project in the watershed.
Early Results Are Strong
Initial results from the Phosphorus Runoff and P-Filter Project are very promising.
According to LEF VP Matt Fisher, the five current filters are removing 95% or more of the phosphorus from the runoff they are treating.
That is a strong early signal that this approach can work.
But the project is not only about what happens in the first few months. Continued monitoring will be essential. LEF and its partners will keep measuring the filters over time so they can understand how much phosphorus they remove across multiple seasons, storm events, drainage conditions, and years of operation.
That long-term data matters.
It will help answer the bigger questions: How well do these systems perform over five years? How much phosphorus can they remove at scale? How many additional High P Fields could benefit from this approach? And how can this model be expanded across the Maumee River Watershed?
The early takeaway is clear: targeted phosphorus filters are already showing real potential to reduce the amount of phosphorus leaving high-risk fields before it reaches Lake Erie.
Why This Project Matters
There is no single fix for Lake Erie’s phosphorus problem.
Nutrient management, cover crops, drainage improvements, conservation practices, farmer education, policy work, and enforcement all have a role to play. But legacy phosphorus fields require additional attention because they can continue releasing phosphorus long after the original buildup occurred.
That is why this project matters.
The Phosphorus Runoff and P-Filter Project gives LEF and its partners a practical tool for addressing one of the most difficult parts of the phosphorus problem: runoff from high-phosphorus fields that continue to feed the watershed.
It is targeted. It is measurable. It works at the field level. And based on early results, it is removing a significant percentage of phosphorus before that runoff can move downstream.
This is the kind of work Lake Erie needs more of.
Not vague promises. Not symbolic action. Real projects, in real places, producing real data and measurable results.
A Model for Future Action
The long-term potential of the Phosphorus Runoff and P-Filter Project is bigger than one field or one installation.
This project can help show how targeted phosphorus reduction can be done in a practical, repeatable way. If more High P Fields and Legacy Fields can be identified, and if more filters can be installed where they are most needed, this approach could become a meaningful part of the broader effort to reduce harmful algal blooms in Lake Erie.
The path forward starts with focus.
Find the fields contributing the most phosphorus. Work with landowners and technical partners. Install systems that capture phosphorus before it reaches the water. Monitor the results. Scale what works.
That is what the Lake Erie Foundation is helping prove through the Phosphorus Runoff and P-Filter Project.
Lake Erie’s water quality problems are serious, but they are not unsolvable. Progress will come from targeted, science-based projects that reduce pollution at the source and create models that can be expanded across the watershed.
The P-Filter Project is one of those projects.
It began with finding the right field.
It continued with engineering the right solution.
And now, with early results showing 95% or more phosphorus removal from treated runoff, it offers a clear example of how Lake Erie advocacy can become direct, measurable action.