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Drought impacts pond water, oxygen levels
By Chance McDavid
MISSISSIPPI STATE -- Decreased water and oxygen levels in Mississippi's drought-damaged ponds could lead to trouble for cattle and fish.
Muddy pond bottoms that occur when water levels fall can cause problems for cattle. Roy Higdon, area livestock agent with Mississippi State University's Extension Service, said cattle sometimes get stuck in the mud while looking for water to drink.
“When cattle get stuck, it is sometimes a challenge to get them out. It's a good idea to try and dig them out first,” he said.
Higdon said reacting too quickly and trying to rope cattle out incorrectly can harm them.
“If a rope must be used, it's best to place the rope behind the front shoulders to limit the amount of pressure on the neck and vertebrae,” he said. “Trying to pull cattle out by the legs puts too much pressure on the joints.”
Water quality issues are often a concern for cattle when water levels get too low.
“Some breeds of cattle like to stand in the water a long time,” he said. “Water quality decreases because low water levels aren't able to dilute cattle urine and feces as effectively.”
Jimmy Avery, Extension professor and aquaculture leader at the Thad Cochran National Warmwater Aquaculture Center in Stoneville, said warm water holds less oxygen for fish than cooler water.
As oxygen levels drop, fish may be seen swimming close to the pond surface at sunrise, appearing to gasp for air. Fish kills can occur when too little oxygen is available for the fish.
“The mechanism that drives oxygen levels is the production of oxygen by algae in the pond,” he said. “The algae produces oxygen during the day and uses some of this oxygen at night.”
Pond algae usually locate within a couple feet of the water's surface. As ponds lose water volume during hot, dry weather, less oxygen is stored during the day.
“Even though less oxygen is stored for nighttime use, the demand for nighttime oxygen is still the same,” Avery said. “This causes a shortage of oxygen for fish.”
Pond managers can improve oxygen in small ponds by using surface-spraying aerators. It is usually difficult, however, to increase oxygen levels in ponds larger than 2 or 3 acres.
“Spraying pond water into the air exposes water droplets to oxygen,” he said.
“To increase oxygen levels enough to make a real difference, it is important to break the water droplets into a fine mist and expose the mist to the air.”
People often try a number of methods to get more oxygen in pond water, but they don't always work. For example, letting water from a well or other source run into a pond through a hose doesn't have much impact on oxygen levels.
“Before adding well water to a pond, it should fall through a series of screens so the water will break into much smaller droplets that contain more oxygen,” Avery said.
Another problem the drought can cause is unwanted aquatic pond plants. These plants can begin to grow in shallow areas of the pond where the water was too deep before, and they can be hard to control once established.
Even though a drought can cause pond owners some headaches, Avery said there are positive points to consider.
“Low water levels give predators like largemouth bass better access to forage species such as bluegill. This situation is similar to a winter drawdown,” he said. “It's also a good time to make repairs to docks or pond levees and get shoreline weeds under control before water levels rise, making control more difficult.”
For more information on pond management, ask for Extension Publication 1428, Managing Mississippi Farm Ponds and Small Lakes at the local Extension Service offices.