Our Lakes Get Older – Water Quality Changes

From the time they were formed, our Minnesota lakes began a natural aging process. As time goes on, lakes are enriched by nutrients and soils from within their watersheds – the land area from which water drains into a lake. Human activities around the lake and within the watershed have sped up the natural aging rate of lakes, primarily by adding nutrient phosphorus. This nutrient, phosphorus, reaches the lake through direct runoff to the lake, in runoff into streams that drain into the lake, through water filtered down into groundwater that recharges the lakes, or through draining wetlands.

Land uses ultimately affect the quality of the runoff and that in turn will affect the quality of the lake water. In our forest areas of Northern Minnesota, with low development and no agriculture, there are minor land use impacts on water quality. But in southern, western and central Minnesota, where there is intense agricultural land use, the increased run off contains larger amounts of phosphorus.

What kind of runoff must be avoided? Along shorelines the following must be avoided: improper operating septic systems, and fertilized lawns and shore land erosion. Away from the shoreline, the following should be avoided: runoff from animal containments, improperly managed chemical applications and irrigation, and pastured livestock that graze directly in a stream. Construction sites must avoid: high erosion, and increased run off as a result of additional streets, driveways and parking lots. Metropolitan areas must try to use only zero-phosphorus fertilizer on lawns.

The Minnesota Lake Association urges all shoreline owners to keep their septic system in compliance, zero-phosphorus fertilizer on lawns and vegetative buffer zones or rock rip-rap along the shoreline.

Clean Water is everyone’s business.