Scientist Finds Lake Willoughby Clear, Clean And Deep

Sep 21, 2015

Northeast Kingdom residents like to boast that Lake Willoughby is one of the clearest, cleanest, deepest lakes in Vermont. Now there’s proof. 

Art Brooks, a retired biology professor from the University of Wisconsin, spends almost every summer day testing water quality and mapping its depths.

Carved out by a glacier, Willoughby Lake looks a little like a Norwegian fjord. It’s prized by swimmers, anglers and boaters. And it’s beloved by Brooks, who grew up around here and even proposed to his wife in a canoe.

To sample the water, he sets out in a wooden motor boat. A GPS depth finder on the dashboard shows a colored diagram of the lake as we head away from shore.

“This orange line here represents the bottom,” Brooks says, peering at the screen. “These echoes we see up here are fish, and sometimes we can see plants growing up from the bottom ... The temperature is 72.12 so we can jump over and enjoy a swim any time.”

Earlier in the summer Willoughby was much colder. The water was higher then and more turbulent after spring rains. On this windless, sunny day it’s unusually clear.

Brooks lowers a metal plate with a black and white pattern on a rope over the edge of the boat. The pattern is still visible at about 30 feet down.

A GPS system on a boat driven by scientist Art Brooks shows a depth in Lake Willoughby of 230 feet not far from shore. Brooks says his mapping shows more depth in spots than the state's outmoded data does.
Credit Charlotte Albright / VPR

“So what I am going to do now with you,”  Brooks says, reaching for more equipment, “is sample a column of the lake water with an instrument that will record the temperature, the electrical conductance of the water, the chlorophyll concentration, which is an indicator of the amount of algae or green material in the water, and dissolved oxygen, or pH. And so this will record this every four seconds as I lower the instrument down in the water.”

All that adds up to just the right chemistry to keep fish healthy. There are no algae blooms here, as in parts of the Lake Champlain watershed. But Brooks is interested in more than the composition of the water. He also wants to know how the depths vary from point to point. That tells scientists and fishermen a lot of about where and which fish are likely to thrive.

Brooks slows down to mark our location on the dashboard depth finder. He’s made 33,000 marks so far – the raw material for his map.

“So it piles all those up and we end up with a good contour map just like you would see if you were mapping the mountains, with the contour lines showing higher and higher elevation. We keep seeing lower and lower depths in the lake,” he says.

All this data will eventually be analyzed and stored in a computer back in Brooks' summer house.

Art Brooks looks out at Lake Willoughby from the deck of his summer home. He says the lake is almost as clean as it was when he began taking measurements about 15 years ago.
Credit Charlotte Albright / VPR

Brooks says his map shows more depth in spots than the state’s outmoded data shows. And he says Willoughby is almost as clean as it was when he began taking measurements about 15 years ago. 

“Well, it’s a big lake and it would take a lot to change it,” he notes.

Soon one thing will change: the temperature. But there's still time and plenty of space for a late summer swim.