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Lake Turnover Events

Updated: Sep 26, 2022

What is the issue?

As some of you are already aware (particularly those that are closer in proximity to the lake), we sometimes experience taste and odor issues with our water during the warmer months of the year. This unpleasantness is due to what is commonly referred to as the “lake turnover” effect. This phenomenon affects most water systems that pull water from a lake or reservoir, particularly those located in the warmer states in the South.

During most of the year, the lake is continually being mixed through wind and waves, which leads to a healthy level of oxygen, which in turn, leads to a healthier aquatic life. During the summer months; however, thermal stratification occurs on our Lake Nottely when the water in the lake forms distinct layers through heating from the sun. The lightest uppermost layer (the shallowest) becomes the warmest and contains the most dissolved oxygen. The cold, dense water at the lake bottom rarely gets any direct warmth from the sun and contains the lowest amount of dissolved oxygen, if any. This bottom layer also contains higher levels of natural occurring nutrients from decaying vegetation and other organic compounds. The middle layer, often called the thermocline, is the transition zone of the water between the upper warm layer and the lower cold layer.

A change in air temperature (a drop or increase of approximately 10-15 degrees) as well as large amounts of cooling or warming rain and/or wind can cause changes to the uppermost layer, causing the water at the surface to become denser than the lower layers. This change in density causes mixing of the layers. This mixing of the layers is essential to re-establishing healthy dissolved oxygen levels in the lake, which our local anglers can appreciate; however, it also causes taste and odor issues as the nutrients/organic matter works it way to the top. This results in a temporary change in water pH, temperature, and dissolved gas levels which can lead to a musty or earthy smell in your drinking water. Please be advised that your water is safe to drink. The taste and odor issues are temporary and will abate as the lake completes its annual cycle. Typically, states in the South can experience two lake turnovers if the conditions are right, one in the spring and one in the fall.

What can be done to fix this issue?

Unfortunately, there is no immediate fix to taste and odor issues associated with lake turnovers, as Mother Nature is at the controls for this particular situation. The sooner the air temperature cools in the fall, and vice versa in the spring, we will see the completion of the lake turnover. However, we do what we can to help this process along. Our staff works diligently to flush affected parts of our water system in an effort to clear out this musty smelling water. We can increase water production from our groundwater wells to blend cooler and more oxygenated water to our system and speed up the process. We appreciate and thank you for your patience and understanding as we navigate through what has become an annual weather-related issue for our water system.

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