Seasonal Water Quality Reminders

Written by David Bradway

Water quality changes to watch for in late summer and early fall

1. Algae
​Algae is an aquatic organism that is present in most water bodies. Increased temperature along with sunlight and excess nutrients (mostly Phosphorous and Nitrogen) can cause algal blooms. You may see algae floating on ponds or covering rocks in streams giving the water a green (or other colors) hue. Some algae can be harmful for humans and animals. If you think you have harmful algae in your lake or pond, contact a water quality professional.

2. Odor
Summer stratification caused by temperature differences in warm water close to the surface and cooler water deeper in a water body prevents mixing in lakes and ponds. This stratification causes nutrients to remain near the bottom of the water body to be consumed by organisms. As the breakdown of nutrients and dead organisms occurs, oxygen is depleted. This anaerobic digestion of nutrients results in hydrogen sulfide gas. When temperatures fall and the water can once again mix, this gas is released resulting in a “rotten egg” smell.

3. Stratification & Turnover
When temperatures are more constant in the summer, water in lakes and ponds will naturally create different zones based on temperature. This is called stratification. When temperatures drop, the water in lakes and ponds cools and requires less energy for mixing. This mixing, also called turnover, can increase oxygen levels by exposing more water to the atmosphere. If a large portion of oxygen in a lake or pond has been depleted during summer stratification, this mixing could dilute the already low amount of oxygen in the water. (Stratification and turnover also happen in winter and spring respectively.)

4. Fish Kills
Fish need dissolved oxygen to breathe. When the temperature of water goes up, the capacity for dissolved oxygen in water goes down. This drop in oxygen can cause susceptible fishes to die. Likewise, when turnover occurs, oxygen can be diluted to unsafe levels for susceptible fishes. 

Staff at the Hamilton County SWCD can assist you with info and suggestions for your water quality concerns including site visits, assessments, and well water testing. Stop by our office or contact us at [email protected]
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