-return to Clean Lakes -

Human Activities Speed Up Lake Aging Process

Lake aging is the natural process by which a lake fills in over geologic time with sediment, silt and organic sediment. These materials can be carried into the lake by the tributary streams, through the air, or come from materials produced in the lake itself. From the time that a lake is built, the aging or filling in process begins. Lakes age (i.e. fill in) at different rates because of differences in runoff and watershed characteristics.

The natural aging of a lake takes places over hundreds of years. However, human activities can greatly accelerate the process. This is called cultural aging. Runoff from urban and agricultural areas may carry effluent, fertilizers, pesticides, and or sediment. These byproducts of human activity can be discharged into a lake and consequently accelerate aging. Most human-oriented land uses, including agriculture and residential and commercial development, contribute to cultural aging.

The adding of excess phosphorus to a lake frequently stimulates cultural aging. Minute amounts of phosphorus, parts per billion, can cause tremendous increases in aquatic plants and algae. This tremendous growth also means a tremendous amount of material that eventually dies and decomposes and is added to the lake.

Typically, any form of land use development contributes more phosphorus to a lake than undeveloped grassland or forested land. Some significant contributors of phosphorus are: phosphate based detergents, lawn and garden fertilizers, improperly sited and maintained septic systems, waterfowl, agricultural drainage, urban stormwater runoff, animal and pet wastes, and road deicers.

Anyone who lives in a lake watershed may take actions to reduce polluted runoff from leaving their property and therefore reduce the soil and phosphorus that reach our lakes. Here are some things to do: Use mulch or plants to protect bare soil, pick up pet waste, reduce the use of fertilizers and chemicals on your lawn and garden, inspect and maintain your septic system, keep grass clippings and leaves out of street gutters, use conservation tillage practices, prevent soil erosion on construction sites, sweep excess fertilizer on walks and driveways back onto the lawn, and wash your car at a commercial car wash.