Green Horizons

Resources threatened by this year's drought include ponds that depend on surface runoff for water. Fish are at risk from high water temperatures, oxygen depletion, increased disease potential and other problems as water levels drop in ponds through lack of runoff and evaporation.

Ponds potentially most at risk are those that depend on water from surface runoff within a watershed that may be too small to maintain a pond's water level even during years of average rainfall. They typically need a surrounding watershed that is about 15 times larger than the area of the pond.

A new MU Extension publication, developed in collaboration with Lincoln University, explains how to monitor your pond and respond to problems. The four-page guide, "Managing Fish Ponds During an Extended Drought", is available online and as a PDF download at www.extension. missouri.edu/p/G9401.

During an extended drought, watershed ponds can lose a lot of water to evaporation and seepage, reducing both the oxygen supply and the amount of living space for fish populations. Long stretches of scorching temperatures make the problem worse. Warmer water can't hold as much oxygen as cool water. A combination of drought and extreme heat can leave ponds with dangerously low levels of dissolved oxygen.

The MU Extension guide, co-written by Charles Hicks, an aquaculture specialist at Lincoln University, describes warning signs of oxygen depletion and discusses how to put more oxygen into a pond with aerators, pumps or, in an emergency, an outboard motor.

"The simplest solution is to use an electric aerator that provides about 3/4 horsepower of aeration per acre of pond area," Hicks said.

Falling water levels also leave a pond's fish with less and less living space. Crowding makes fish more vulnerable to stress and disease. Nutrients and waste products become more concentrated as the pond shrinks, further increasing the risk of oxygen depletion, disease outbreaks and other problems, said Hicks.

Landowners can reduce the chance of fish kills by keeping livestock out of the pond and avoiding the overuse of fertilizer in the watershed. Wise watershed management and proper design and construction of the pond can lessen the impact of drought, said Pierce.

Although the summer drought has taken its toll, there may be some upsides to these conditions that have lowered pond and lake levels, particularly in ponds deep enough for fish to survive. The low water conditions this fall will provide optimal conditions for pond owners to make improvements, such as deepening pond edges to discourage unwanted vegetation and repairing pond dams to prevent water seepage.

For more information, contact your local MU Extension center. Detailed information on pond management is available from the Missouri Department of Conservation at www.mdc.mo.gov/node/3311.