Murky Green Lake raises questions — and answers

Citizen scientist Wayne Nowicki uses a Secchi disk to measure Green Lake’s water clarity at his favorite fishing spot. Data collected is used in combination with water-clarity readings collected by the U.S. Geological Survey to track both long-term and seasonal trends on the lake. submitted photo

by Alison Niescier

Six feet of water clarity is not what Don Bogdanske, Green Lake Association (GLA) citizen scientist, environmental educator and area resident expected to find midway between the Heidel House and Sandstone Bluff last month during his monthly monitoring.

“This year’s clarity is not what I would consider normal,” explained Bogdanske. “In years past, I’ve seen readings of over 10 feet up to 40 feet.”

Not alone in his assessment, several volunteers from the GLA’s citizen science program similarly reported shallow water clarity on Big Green. In fact, decades of monitoring by the U.S. Geological Survey indicates an average of 15 feet is more typical for Green Lake this time of year.

Water clarity is an important indicator of lake health, as shallower clarity is a reflection of increased algae growth. An abundance of algae decreases oxygen levels and can be harmful to plants, insects, fish and wildlife.

In extreme cases, excessive algae results in blue-green algae blooms that can be harmful to human and animal health.

An increase in more extreme rainfall events is to blame for the extra murk this month.

The Wisconsin State Climatology Office shows that Green Lake has received 3 to 4 inches above average in just the past month alone, which is in line with heavier rain across all of southern Wisconsin.

“Mother Nature has not been kind to Green Lake this spring,” said Stephanie Prellwitz, GLA executive director. “We had a fast-melting May snowfall, several intense rainstorms and a stretch of heatwave days.

Altogether, this created the perfect conditions for extra nutrients to accelerate algae growth in the lake.”

In addition, a culmination of several wetter-than-average years has increased algae blooms in Green Lake and in lakes across the state. These intense rain events carry phosphorus-laden soil into nearby creeks and streams, where it eventually ends up in Green Lake.

While the rain cannot be controlled, the GLA and the lake management planning team are working on what can be controlled: Using conservation practices on the land to combat runoff and nutrient issues in the lake.

Among other benefits, these best-management practices reduce the amount of nutrient-loaded runoff that makes its way to Green Lake.

Bogdanske embraces his role in this larger effort. He and his fellow citizen scientists watch the lake closely, looking for indications that these conservation practices are making a lasting dent on Green Lake’s long-term health.

The public is invited to attend the GLA’s annual meeting on Saturday, June 16 from 9 to 11 a.m. at the Goose Blind Grill & Bar, where the organization will showcase ongoing efforts to improve the lake’s water quality.

Alison Niescier is the project manager for the Green Lake Association, a local not-for-profit that works to improve water quality for Green Lake.