Summer Water Levels

Emerald Lake’s water level is currently hovering near what is the designed "full pool” capacity. During the summer months, when evaporation rates are at their highest, it is typical for the lake level to drop significantly during dry spells. Unfortunately, sediment accumulation has made these dry spells much more noticeable than in past years. At times it will become difficult to navigate portions of the lake, and some lakeside property owners could lose water access and may have to temporarily resort to launching their boats from the community boat ramp. Boaters should also take more precautions to remain alert to sunken logs, rocks, irrigation pipes and other underwater hazards.

Because of its vital role in maintaining the safety and integrity of the dam, the valve on the pipe in the center of the dam will not be closed to raise the water level to satisfy navigational access or irrigation use of the lake. To help our residents understand the importance of keeping the valve open, I am providing a basic overview of our dam's structures and function.

The dam consists of three main components: the embankment, the principal spillway (the pipe running through the center of the embankment), and the emergency spillway (the concrete apron/creek channel located at the east end of the embankment).

"Over-topping" of the embankment is one of the leading causes of catastrophic collapse, accounting for 34% of all dam failures in the U.S. The spillways function to pass water out of the lake to maintain a safe vertical distance between the designed "full pool" capacity (the amount of water the dam was constructed to hold on a regular basis) and the top of the embankment. This margin of safety on a dam is called the "freeboard."

"Full pool" is reached when the water level is at the crest of the pipe and little to no water is exiting the lake.

As the water level rises above the crest of the pipe, water will begin to passively exit the lake through the pipe. As flow through the pipe reaches a maximum, water will begin to flow over the emergency spillway.

The pipe was designed to serve a dual purpose. With modification, it can be used as a siphon to draw down the lake level to facilitate repairs to the dam, dock construction, dredging, or other needs.

Significant rainfall events in the southeast are common and unpredictable. The effectiveness of having both of Emerald Lake's spillways in operation was quite evident this spring when our area was unexpectedly hit with two flash floods. Shoreline flooding would have undoubtedly been much worse had the valve on the principal spillway been closed. Furthermore, with both systems in operation, submerged docks were quickly uncovered after the storms thereby avoiding water-related damage, such as warped deck boards.

I hope this satisfies any questions or concerns about the fluctuations in the lake level. I ask that you please notify me, Scott, or Don immediately if you see anyone tamper with the principal spillway valve or notice that it is not in operation.

Thank you.

Sharon