Ice must leave for second sampling
By Vicky Wedig
Editor
If the ice ever melts on Delavan Lake, the U.S. Geological Survey will conduct its second sampling of water from the lake this year – a check-up of sorts of the lake’s health.
From his computer screen in Madison, USGS research hydrologist Dale Robertson can view an automated gauge on Jackson Creek at Mound Road and see whether water is flowing into the lake or still frozen.
Since 1983, the USGS has monitored the water quality of Delavan Lake. Robertson compared the testing to annual physical exams by a doctor. When a physician has seen a patient for three decades, any changes in the person’s health are apparent.
With 30 years of data about the clarity, algae and nutrients in Delavan Lake, the USGS can keep tabs on any changes, Robertson said.
The USGS tests the water eight times a year. The first was done in February on the frozen lake. The next is scheduled for April provided the ice is broken up and the water is completely mixed, Robertson said.
Sampling is then done in May, June, July, August and November. Robertson reports the results to the Town of Delavan’s Lake Committee late in the year.
He said the water quality in the lake has gotten worse over the past 15 years but is not as bad as it was in the 1980s.
“The lake was in pretty bad shape in the early ‘80s,” he said.
After the lake rehabilitation in 1989 when the lake was drawn down and all the fish eliminated and restocked, the water quality was impeccable.
“It was almost like a swimming pool,” he said.
He said the clarity of the water has declined from that state but not to the level it was in the ‘80s. He said algae in the lake was fairly high last year, but the fishery is still good.
The Lake Committee set forth specific goals for the lake several years ago in terms of clarity and amounts of algae and nutrients, Robertson said. Algae and phosphorus levels are similar to the town’s goals, and water clarity is, on average in the summer, a little bit better than the goal, he said.
In June, the water clarity is above the goal, but in July and August, the clarity declines as algae grows and is below the goal, Robertson said.
The testing
The town pays for $15,000 of the $18,600 yearly cost of monitoring, and the USGS pays $3,600.
The USGS has a station on the lake that it goes out to eight times a year, Robertson said. It samples the water in three locations – the “deep hole” near the center of the lake and locations on the north and south ends of the lake.
Last month, when the lake was frozen, hydrologists measured from the surface of the ice to the bottom of the lake and collected samples at various depths, Robertson said. In the middle of summer, an analysis is done for plankton.
The USGS along with the Delavan Lake Sanitary District also monitor locations in the watershed to determine what’s coming into the lake from its tributaries, said Town Board Chairman Ryan Simons. The DLSD funds that portion of the testing.
Water in the creeks is continually monitored by gauging stations on Mound Road and at Highway 50 that measure the nutrients running into the lake, Robertson said.
