How healthy is our lake?

To check the level of lake health every June and August
LPA volunteers collect lake water samples for
Chlorophyll-a, Phosphorus, Nitrogen, and Clarity.


These samples are sent to the state health lab to provide
ongoing nutrient load data. Too many nutrients cause
increased growth of algae and large aquatic plants.


High levels of phosphorus lead to excessive algae
growth which produces harmful toxins to human and
animal health.


Phosphorous is a beneficial mineral that is found in our
bodies, our food, and in the environment. All aquatic
plants and animals need it to grow. However even small
amounts of increased phosphorous to a lake causes nuisance algae and plant growth. Excessive phosphorus can lead to toxic bacteria and algae blooms, depleted oxygen levels so that plant life and fish do not flourish. This creates dead zones in the water.


Phosphorus sources may include feedlots upstream, failing septic systems, excessive quantities of geese, dumping waste directly into drains or ditches, even letting children in diapers play in the lake or throwing pet waste into the lake. Pet Poo is not the same as fish poo. 


Phosphorus and Soil Erosion

Soil erosion is a major contributor of phosphorus overload in lakes. Phosphorus binds to soil particles and enters lakes as runoff from snowmelt and rainfall. Lake homes have replaced native plant buffers and filtering wetlands with lawns, gardens, riprap and retaining walls. Runoff carrying phosphorous loose soil have less chance of being filtered before reaching the water and adds to the sediment build up in the lake.


Chlorophyll-a is the primary pigment of photosynthesis in algae.
Testing the lake water for Chlorophyll-a measures the amount
of algae growing.


Water clarity is measured with a secchi (sec-kee) disk, which is
lowered into the water until the disk disappears.  The distance
from when it disappears is the water clarity reading.


Nitrogen is a natural occurring nutrient in aquatic ecosystems.
Excess nitrogen can cause overstimulation in growth of aquatic
plants and algae. Excessive growth of these organisms, in turn,
can use up dissolved oxygen as they decompose, and block light to deeper waters. Limiting nutrient pollution will protect people’s health, the local economy, and safe water for swimming and fishing.


PO Box 222, Lake Norden, SD 57248



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