Editorial: Help Lakes Drain to Prevent Future Floods

In case you missed his editorial in Sunday’s Wisconsin State Journal, Dick Lathrop (who spent four decades with the Wisconsin DNR studying the Yahara lakes and holds an honorary appointment with the Center for Limnology) had some thoughts on lake levels and flooding:

by Dick Lathrop — Much good reporting has been done about the unprecedented flooding in the Yahara lakes.

People say they want lake levels lowered, especially in Mendota to temporarily store runoff that comes from its large watershed. But rewriting Department of Natural Resources rules to lower Mendota’s summer levels isn’t the answer. Getting rid of excess water from the downstream lakes is the problem. If Waubesa empties, then Monona drains and Mendota can release water faster. Currently, water can’t drain out of the lower three Yahara lakes fast enough due to poor river channel hydraulics with numerous pinch points and flow restrictions.

I have studied the lakes for over four decades and served on two Yahara Lake Advisory Groups dealing with lake levels. Lake levels routinely are lowered in fall to prevent shoreline ice damage. Fishery interests want refilled lakes by April and boaters want high water by May. By June, water levels in all lakes are supposed to be within the summer operating range set by DNR — a range of 6 inches for each lake. However, a rainy spring and/or summer pushes lake levels above maximums, making it difficult to lower the lakes in fall.

Dane County has an extensive lake level and river flow monitoring network operated by the U.S. Geological Survey. Data from September 2017 through August 2018 identified reasons for the flooding. Heavy rains in fall 2017 kept lake levels so high that by January the lakes were still two feet higher than winter minimums. Then big runoff events (from rain on frozen ground) occurred in January and February raising all four lakes to summer maximum in March. A rainy May and June kept lakes exceedingly high all summer until the Aug. 20 rainstorm produced the catastrophic flooding.

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