Water Quality

A lake's water quality refers to how free from contaminants it is (clarity) and how well it can support its natural aquatic ecosystem.

What harms water quality?

Nutrients

Nutrients such as phosphorus and nitrogen come from sediments (eroded soil), manure, pet wastes, improperly maintained septic systems, fertilizers, grass clippings, and leaves.

Phosphorus, whether from natural sources or commercial fertilizers, is plant food. Too much phosphorus in our lakes causes excessive aquatic plant growth and algae blooms (where lakes turn green).

Excess algae can reduce desirable bottom-rooted plants by blocking sunlight. When algae, plants, and other organic materials decay at the bottom of lakes this depletes oxygen in the water, making it difficult for fish and other aquatic life to survive. Reduced oxygen levels also contribute to winter fish kills in shallow lakes.

Most Wisconsin lawns and soils already contain adequate— and often excessive— amounts of phosphorus.

Sediments

Sediments are soil particles eroded from construction sites, developed areas, and cropland. Sediments can also include flakes of metal, debris, and toxics washed off city streets and parking areas. Sediments:

• cause the water to become cloudy, or “turbid,” making it difficult for fish to see and feed properly.
• cover plant leaves, reducing the amount of sunlight reaching desirable aquatic plants.
• damage fish gills and impair the feeding and breathing processes in aquatic insects that fish eat.
• bury fish spawning areas and other valuable aquatic habitats.

Why is water clarity important?

Water clarity is a measure of the amount of particles in the water, or the extent to which light can travel through the water. Water clarity affects

• the ability of fish to find food
• the depth to which aquatic plants can grow
• dissolved oxygen content
• and water temperature

Water clarity is often used as a measure of a lake’s productivity level and an indicator of ecosystem health.

There are many ways to express water clarity, including Secchi disk depth, turbidity, color, suspended solids, or light extinction. Chlorophyll, a pigment found in all plants, is often used to determine the amount of algal growth in the water and is related to water clarity as well.

Several studies, notably one on Lake Delevan Wisconsin and another on selected Maine lakes, have shown that good water quality and clarity is linked to higher property values.