Old Filled-In Ponds
Old Filled-In Ponds
Many ponds that are 20-30 years old have filled in so extensively that they are shallow with vast areas of aquatic vegetation. Ponds are temporary features on the landscape because they accumulate silt, debris, and decaying vegetation, eventually becoming marshes and even dry land. Although filling is inevitable, some measure can be taken to slow down the successional process.
If a pond is reclaimed that has received excessive amounts of silt from erosion, soil conservation measures such as terraces, grassed waterways, and minimum tillage should be implemented. Small dams can also be built just upstream from large impoundments to act as settling basins for silt.
Livestock trampling the shoreline can cause the pond’s banks and the dam to slough in. In addition to benefiting fish production, the practice of excluding livestock from the pond also increases the life of the pond.
Aquatic vegetation settles to the bottom when it dies. Part of it decays, but a considerable amount of residue remains on the bottom, filling a pond in over several years. Vegetation control slows this process.
Ponds that are filled in can be renovated, but the process is expensive. It is often easier to build a new pond if other good sites are available. If the pond is located at the only good site available, it can be deepened by dredging with a drag line. A cheaper method is to drain or pump the water out of the pond and let the bottom dry. If the bottom muck is too deep it will dry very slowly, and the pond will fill with water before the bottom gets a chance to completely dry. In most cases, it is best to break the dam with a back hoe down to a level below the pond bottom. After drying for about a year, the pond bottom should be firm enough for a bulldozer to push out the sediments. This material can be pushed out to the back side of the dam and the break can be patched and packed with clay soil. It is important to “stair step” both sides of the break from bottom to top and compact each layer of added clay separately. The pond side of the dam should also have a new layer of soil pushed up against it and packed to be sure the dam is resealed.