Lake Leaders Gain Powerful New Tool to Reveal “Invisible” Phosphorus Threat Beneath Their Lakes
Harvard-bound Libertyville High School graduate partners with Lake County Lake Lovers to build first-of-its-kind internal phosphorus calculator
Serendipity has a way of showing up at just the right moment. For Shubh Varshney, a 2026 Libertyville High School graduate preparing to enter Harvard College this fall, a chance meeting with leaders from Lake County Lake Lovers sparked a summer project that will benefit lake communities across Lake County for years to come.
Lake County Lake Lovers—a nonprofit dedicated to improving the health of local lakes—has worked for four years to address a sobering reality: over 70% of Lake County’s 173 lakes are classified as impaired by the Illinois EPA. Their volunteer-driven water quality monitoring program equips everyday residents with professional-grade equipment and training to generate decision-quality data from April through October. These volunteers also meet monthly to learn, collaborate, and share insights.
At the May 2026 Tech Team meeting, Shubh joined volunteers as Water Quality Lead Paul Spiewak taught attendees how he had calculated his lake’s Internal Phosphorus load using renowned limnologist Dr. Gertrud Nürnberg formulas, whose 40 years of research on internal phosphorus loading has shaped lake science worldwide. Internal phosphorus loading is the “legacy” phosphorus reservoir that has built up over years and decades in the lake bottom. The formulas helps lake teams estimate how much phosphorus is released each year from lake-bottom sediments—an “invisible” source of pollution that often goes undetected.
Internal Load = Surface Area × Anoxic Factor × Release Rate
Besides needing to know Surface Area (the easy part), Paul showed Gertrud’s formulas to calculate the Anoxic Factor (how many days the Dissolved Oxygen gets so low it causes a chemical reaction making the typically iron-rich minerals to release the bonds holding the element Phosphorus) and the Release Rate (the speed at which phosphorus is actively released per day from the anoxic sediments and into the water column); some attendees were not so convinced that all one needed for success was “just a calculator”!
That sparked an idea.
What if Shubh could build a user-friendly digital tool—a simple front end paired with a programmed back end—to make Dr. Nürnberg’s formulas accessible to any lake leader?
Within a week, Shubh’s sponsorship letter was submitted, and he began a 10‑week Harvard Summer SPARK Project, with weekly mentorship from Lake Lovers, creating a win‑win: real-world experience for an incoming Harvard freshman and a powerful new resource for Lake County’s lake communities.
Why Internal Phosphorus Matters
Across the United States, 50% of lakes are impaired, and in Lake County, that number climbs to 70%. The leading culprit is nutrient pollution—especially phosphorus.
Phosphorus fuels algae growth. In fact, one pound of phosphorus can generate 500 pounds of wet algae (Wetzel, Limnology, 2nd Edition). When algae blooms become excessive or toxic, they can harm wildlife, threaten human health, and degrade lake ecosystems.
Phosphorus enters lakes from two primary sources:
External loading — leaking septic systems or sewer pipes, fertilizer runoff from farms, golf-courses and lawns, storm sewers, or streams
Internal loading — phosphorus trapped in lake-bottom sediments that is released when temperatures rise and dissolved oxygen drops
Internal loading can sometimes be the largest source of phosphorus in a lake, yet it’s the hardest to measure—and typically requires expensive consultants.
Shubh’s project changes that.
Building the Internal Phosphorus Calculator
Shubh’s mission was clear: Create a web-enabled portal with intuitive drop-down menus that allows lake teams to enter key data and instantly receive an estimate of the annual internal phosphorus released, expressed as pounds of Phosphorus and pounds of algae.
The back end would be powered by Dr. Nürnberg’s calculations, published in her 2025 book Lake Functioning. Dr. Nürnberg herself met with Shubh on June 23 and continued to provide guidance following the interview.
Shubh worked under the technical advisement of:
James Bland – former U.S. EPA, founder Integrated Lakes Management, volunteer researcher at Shedd Aquarium, and lake manager for 45 years
Allen Melcer – former environmental manager, U.S. EPA
Becky Sawle – former AbbVie Innovation Projects Lead
Paul Spiewak – former analytical chemist & science enthusiast
User testing took place in July with lake teams from Loch Lomond, Lake Catherine, Long Lake, and Cedar Lake, all part of the 2026 Lake Lovers Water Quality Monitoring program. Their feedback helped refine the tool’s usability and accuracy.
A Breakthrough for Lake Management
The final calculator is now live at: www.LakeCountyLakeLovers.org/calculator
After entering a few inputs, lake teams receive a clear, printable report showing:
Estimated Internal Phosphorus Loading as pounds of Phosphorus per year
Pounds of wet algae produced by that internal Phosphorus
Total Phosphorus detection limit interpretation
Osgood Index (indicating how likely the lake is to stratify)
This information is transformative. As lake expert James Bland put it, the impact is “incredible.”
Lake leaders can now get a reliable estimate, or range of estimates, of internal phosphorus and see what was previously invisible—how much phosphorus is coming from within their lake. This empowers communities to:
Understand how large their annual internal phosphorus problem is compared to their amount of external phosphorus
Consider if treating internal phosphorus is a “better bang for the buck” in their lake management plan
Avoid spending money on the wrong mitigation strategies
Prioritize actions that will meaningfully improve lake health
Accelerate lake recovery by focusing on internal loading when it is the dominant source
In many cases, lake associations invest heavily in external loading solutions while internal loading continues unchecked. Shubh’s calculator helps prevent that misalignment.
A Summer Project with Lasting Impact
What began as a simple question—“Could we do this?”—has become a powerful tool for environmental stewardship across Lake County and beyond, as anyone is welcome to use the calculator for no cost.
Shubh Varshney’s Harvard Summer SPARK Project demonstrates how curiosity, collaboration, and community engagement can produce meaningful impact. His work will help lake teams make smarter decisions, save resources, and help to improve the lakes that define Lake County’s identity.
And perhaps most importantly, it shows how one student’s initiative can ripple outward, improving ecosystems and communities for years to come.