Building a pond mix of science, art

The best site for a pond is a spot where the smallest dam possible impounds the largest possible amount of water.

Once you identify that site, other considerations come into play, said Scott Jones, small impoundment extension specialist for the University of Arkansas Pine-Bluff. Soil composition and substrate characteristics are crucial.

“Preparing the basin is as important as preparing the dam site,” Jones said. “Make sure the soil will actually hold water.”

The first step is to remove all of the topsoil in the impoundment area. Make sure there’s no rock formations, and make sure there is enough clay. Clay composition of 20%30% is ideal, Jones said, but too much clay is bad because it is too erodible. In northern Arkansas, rock veins can compromise a basin, especially limestone that dissolves when it is inundated.

“You want a mix of some gravel, clay and sand to make a soil that’s fairly stable, that compacts and holds water,” Jones said.

Next, a soil sample will tell you if you need to fertilize your pond. Soil in Central Arkansas is acidic, so ponds in Central Arkansas are acidic. Acidity limits productivity.

“If you’ve got a Ph in the 5 or low 6 range, a lot of times you can benefit from applying agricultural lime to that basin before it fills up,” Jones said. “It’s a lot easier to do that treatment when a pond is being built.”

To compact the soil in the basin, Jones recommends a spiked roller like that’s used in road construction. A bulldozer does not compact soil efficiently, Jones said, because the machine is designed to distribute its weight over a large area. A bulldozer spreads dirt. It does not compact dirt.

Also, you need to slope the banks properly. Jones recommends 3:1 slope, meaning that depth increases 1 foot for every 3 feet of distance from the bank.

“That is stable, and you don’t have to deal with vegetation as much,” Jones said. “Anything steeper than that, and the bank erodes. Wave action will tear the bank up faster.”

A pond need not be deeper than 12 feet, Jones said. During hot weather, water stratifies, and the deepest layers of the water column become anoxic, containing no oxygen. Fish do not inhabit anoxic water. Also, the bacteria that break down plant matter are aerobic, requiring oxygen. In an anoxic environment, leaf litter, pine needles and all the other plant matter that enters a pond accumulates on the bottom, gradually decreasing depth.

“That’s where all the junk is that needs be recycled, but there’s no decomposition going on,” Jones said. “A pond that’s reproductive for 10 or 15 years gets shallower and shallower. Weeds become a problem, and eventually it reverts to a swamp. Nature wants to take a pond or lake back to wetland and eventually back to land.”

Installing aerators will prevent anoxic problems and increase productivity throughout the water column.

Depth provides fish refuge from sun and heat in the summer. Installing cover and structure concentrates fish. When preparing your basin, you will remove large rocks, tree trunks and stumps. You can put them back, Jones said, after you prepare your basin. It’s better, he added, to build a few big structures rather than distribute a lot of small structures around a pond. You can also build spawning beds around the lake at the 3-foot depth mark, keeping in mind that spawning habitat requirements for bluegill are different than those for bass.

Properly managed and maintained, a pond can provide excellent fishing for decades.