LAKE DRAWDOWNS: WHAT THEY ARE AND WHY FLORIDA’S LAKES NEED THEM

December 1, 2004
CONTACT: Sam McKinney or Joy Hill (352) 732-1225

What are lake drawdowns and why do we need them?

That is a question many people ask the Florida Fish and Wildlife Conservation Commission (FWC), particularly when one’s favorite lake is scheduled to be drawn down.

A drawdown is a technique used by lake managers to enhance fish and wildlife habitat by radically reducing water levels in a lake to expose the mucky sediments on the bottom so they can dry out and compact. Drawdowns usually last several months and are typically done in the winter during Florida’s dry season.

After the muck has compacted and firmed up, the lake is gradually refilled and new, desirable plant communities begin to grow in the firm bottom. A firm lake bottom is what fish need to spawn and what desirable aquatic plants need to take root and grow - two components critical to a good fishery.

Unfortunately, when lake levels are artificially stabilized for flood control and other reasons, and are not allowed to fluctuate, the lake bottom never gets a chance to dry out. As a result, plant and other organic materials decompose and create a thick layer of muck that hampers spawning and plant growth. In addition, this soft, sludgy sediment reduces the number of invertebrates, which are vital food for young fish.

The FWC and other water managers use drawdowns to help reverse these problems. The extended periods of low water levels expose the lake bottom near the shoreline and allow it to dry out. In some cases managers use heavy equipment to remove the exposed thick muck and then plant beneficial aquatic vegetation the fish and wildlife need in the remaining firm bottom. In other cases the muck is left in place to dry and harden, and the beneficial plants return naturally.

These human-created drawdowns are designed to mimic nature, which uses extended periods of drought to naturally draw down lakes. Who can forget the severe droughts of the late 1990s? Lakes dried out, and many people complained. But those in the know understood that while the drought was causing some immediate problems, the long-term effects for the state’s lakes was great.

Why? Because while the lake levels fell, their mucky bottoms were exposed to the hot, dry air, which dried out the bottoms and hardened them so when the inevitable rains returned and refilled the lakes, the beneficial aquatic plants could take root. Those plants provided new habitat for aquatic fish and wildlife, and the hard lake bottoms gave fish suitable places to spawn. 

During drawdowns, such as the one the Florida Department of Environmental Protection is currently conducting at the Rodman Reservoir, the FWC often implements no-harvest or restricted-harvest rules primarily for black bass. During drawdowns, fish are vulnerable to both over-harvest and natural predation because the lowered water level causes them to concentrate in smaller areas. Such temporary restrictive rules are favored by anglers who have reported seeing too many large and trophy-sized bass taken out by some anglers during these vulnerable times.

In the end, although they may present a temporary setback for anglers, drawdowns, whether naturally occurring or human-induced, are a critical component to keeping Florida’s lakes healthy and alive.

JMH/CR