Presentation on theme: "Perspectives on the Phosphorus Problem in Lake Champlain Eric Smeltzer"— Presentation transcript:
Perspectives on the Phosphorus Problem in Lake Champlain Eric Smeltzer
Why is phosphorus a problem in lakes? Low Phosphorus ~10 µg/L Very high Phosphorus > 50 µg/L High phosphorus Medium phosphorus
Why are excessive algae a problem in lakes? Impair recreation and aesthetic enjoyment Impair water supply Alter the ecosystem Blue-green algae (cyanobacteria) can be toxic
A blue-green algae (cyanobacteria) bloom
Phosphorus concentrations and trends in Lake Champlain
Sources of phosphorus loading to Lake Champlain, Vermont nonpoint sources (68%) Vermont wastewater (2%) New York wastewater (3%) New York nonpoint sources (19%) Quebec wastewater (<1%) Quebec nonpoint sources (8%)
Long-term trends in Vermont wastewater phosphorus loads to Lake Champlain
Long-term trends in phosphorus loading to Lake Champlain from all sources
Lake Champlain Basin Land Use
Phosphorus loading to Lake Champlain by land use type
Why does it take so long to see results?
It takes several years for vegetation to become established.
Phosphorus has accumulated in the soils of some farm fields after decades of over-fertilization. It can takes many years for soil phosphorus concentrations to decline even after proper nutrient management methods are implemented.
Federally-subsidized superphosphate (in tons) brought into Vermont for farmers to apply to fields.
Images from the Landscape Change Program Deforestation and over-grazing in Vermont during the 19 th century caused tremendous erosion of upland soils.
There is an historical legacy of alluvial sediments deposited along Lake Champlain Valley rivers. These sediments are continuing to erode, and even with proper river corridor protection measures in place, it will be decades before stream stability is fully restored.
Decades of excessive phosphorus loading can create the conditions for internal phosphorus loading in places like St. Albans Bay and Missisquoi Bay. Internal loading delays the recovery of the bay in response to load reductions from watershed sources.
Changing farming practices and other landowner behavior sometimes takes the transition of a generation.