Road salt research update: Which lakes are saltiest?

Report updates data on road salt’s effects on Adirondack lakes in Lake Champlain basin

By Zachary Matson

New research supports an understanding of how Adirondack lakes in the Lake Champlain basin suffer from road salt use, particularly on state roads.

Adirondack Watershed Institute researchers and volunteers with the Adirondack Lake Assessment Program last year sampled 76 lakes in the basin, most of which had not been assessed in at least 20 years. The group released a report that provides the latest evidence of increased sodium and chloride levels of water bodies and threats to aquatic environments. 

AWI found 28 lakes with moderate or high salt influence, above 10 milligrams per liter, a level scientists consider a threshold at which changes may happen to a lake’s ecology. The new data strengthens the understanding that road salt has polluted numerous lakes across the Adirondack Park, which scientists first outlined over a decade ago.  Background or natural chloride levels in Adirondack lakes are expected below 1 mg/l, according to scientists.

“The lakes that we knew were affected by salt, that is further confirmed by this work,” said Brendan Wiltse, AWI’s senior research scientist. 

The salt pollution is especially acute in watersheds with high state road density. Maps of watershed development included in the report show the road networks surrounding the saltiest lakes.

In Essex County, the Northway passes within hundreds of feet of the eastern shore of Augur Lake, one of the basin’s most impacted by salt. Rush Pond in Warren County, a lake AWI had not previously examined, fell just short of measuring chloride levels of 40 mg/L, the threshold to be considered high impact. Rush Pond also sits just off the Northway, near Six Flags Great Escape and State Route 9 in Queensbury. 

Six lakes in the basin measured chloride levels at the high level: Augur Lake, Big Cherry Patch Pond, Butternut Pond, Lake Colby, Lower Cascade Lake and Upper Cascade Lake.

Lake Colby last year registered the highest chloride levels in the parkwide ALAP survey, averaging 59 mg/L, according to ALAP data.

The Champlain basin report includes data from a standard suite of water chemistry and other measures, including total phosphorus, water clarity, the presence of invasives, watershed development and water pH.

The survey, funded by a grant from the Lake Champlain Basin Program, could also serve as a model to assess lakes in other large watersheds and drill down on ones in need of deeper study, Wiltse said.

Some of the park’s largest and most visited lakes have detailed lake management plans on record, but hundreds of other lakes don’t have any plans that outline challenges or inform management decisions. The process is too expensive. 

“That’s not scalable, we can’t develop those for every single waterbody in the Adirondacks that have a concern or issue,” Wiltse said. 

Instead, AWI researchers hope they can find a middle ground for sampling and data analysis on many more lakes. Using last summer’s survey to prioritize followup work, AWI and the basin program identified three lakes for action plans: Mirror Lake, Lake Colby and Lake Roxanne.

The plans will include more data collected this summer, including comprehensive mapping of the lake’s aquatic vegetation, and meetings with lake stakeholders about the issues they see and ways to protect the lake. The plans will identify specific projects – like strengthening shoreline buffers or improving storm runoff – that communities could implement in the years to come. 

“The intent with these is to be a bit more concise and action oriented in giving stakeholders a roadmap of what to be focused on,” Wiltse said. 

Editor’s note: This story was updated to clarify background chloride levels in Adirondack lakes.