Over the last two weeks, Lake Monona, Lake Waubesa, and Lake Kegonsa have all entered into their annual rite of spring’s clear-water phase. Lake Mendota, however, remains a murky mystery. Why are the downstream Yahara lakes so clear, when the lake at the top of the chain isn’t? Perhaps more important, are we going to miss Mendota’s clear-water window this year?
Not necessarily, says Ted Bier, research specialist for the North Temperate Lakes Long-Term Ecological Research program. “Mendota was right on the cusp of moving into a clear-water phase over Memorial Day weekend,” Bier says. “But then it got slammed by that last storm.”
If you need a refresher (or aren”t here in Madison) that storm dumped 1 to 2 inches of rain on our fair city in a two-hour span. And all of that water ended up in our lakes, carrying sediments and nutrients that can cloud the water. Sediments can take several days to settle out to the bottom, especially if windy conditions keep them suspended, says Bier. And that sudden influx of nutrients can cause algal blooms.
People around the lake have been noticing. My office, for example, usually affords me a view of carp congregating just off shore for their annual spawning run (million-dollar view, I know). This year, all I can see are ripples on the green surface. The Clean Lakes Alliance recently shared a picture one of their members took of a greenish brown boat wake in Mendota – the result of algae being churned up to the surface by its propellers. Continue reading