Published by Vermont Public Radio
With a surface area of 435 square miles stretched over a length of 120 miles, Lake Champlain is one of the largest lakes in North America. Its waters support aquatic ecosystems, recreation, agriculture and public water supplies.
But high levels of phosphorus in the water threaten all these uses of the lake. A plan to clean up Lake Champlain proposes limiting phosphorous runoff, which causes potentially toxic blue-green algae to proliferate. The plan is called the Total Daily Maximum Load, or TMDL.
The limits apply not just to farms and developments (although those are the leading contributors of phosphorus to Lake Champlain), but also to wastewater treatment plants, back roads and even forests and streams. Runoff from all these sources throughout a 8,234-square-mile watershed in Vermont, New York and Quebec ends up in the lake.
A new proposal, referred to as Total Maximum Daily Loads (TMDL), is a choice between scenarios that allow different amounts of pollution from various sources to enter specific parts of the lake. It’s a long and technical document; this series of interactive graphs and charts explains the basics of the official plan — which is not without controversy.