Water Sources: Common questions about dry ponds
Extended dry and drought periods offer landowners a chance to inspect the bottom of their ponds and consider cleaning out sediment or fixing a pond so it holds water better. The following questions raise important issues to think about before beginning costly renovations.
Q.How much are you willing to spend to improve the pond’s usefulness?
A.Ponds are expensive, both to build and rebuild. Ponds place livestock at risk of falling through ice or getting stuck in mud while attempting to drink. Even with good construction methods, some ponds do not hold water well. Ponds require considerable ongoing maintenance. Sediment removal costs about $10 per cubic yard. The best pond maintenance practice is to fence off the pond from direct access by livestock and place a waterer below the dam to use the pond water. This minimizes damage to the dam, reduces silting into the pond, and maintains water quality. The fenced-off area and the rest of the pasture should be kept free from water-sapping trees and brush.
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Q.Is it less expensive to remove sediment from the pond or build a new pond elsewhere in the pasture?
A.The “best” pond site is generally where the existing pond is located. If another suitable site is available in the pasture, it likely to be less expensive to build a new pond rather than clean the sediment from an existing pond. When comparing costs, be sure to include fencing around the pond and a below-dam watering facility in the estimate.
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Q.Is the purpose of the pond to provide drinking water to livestock?
A.Many ponds were installed to provide drinking water for livestock. Other water sources may be available that offer reliable livestock water. Consider using a pressurized system from a public water supply or on-site well, or using a pond as a fenced-off water supply for a pressurized system. Compare costs for various options before beginning pond renovations.
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Q.Where will the sediment removed from the pond be placed?
A.Sediment from the bottom of a pond is often sludge-like and may need time to dry before it can be used. Often, the best place to put the sediment is on the back side of the dam. Other potential uses include filling nearby gullies and ruts. To avoid livestock from getting stuck, a temporary electric fence can keep livestock out of the deposited sediment until it dries. Avoid placing sediment near or upslope of the pond because it will wash back into the pond.
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Q.Can the sediment be used as a building or topsoil material?
A.Pond sediment has little soil strength, making it unsuitable for use around or under a foundation. It can possibly be used to fill in eroded sites.
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Q.Is the pond located on a site that will hold water?
A.Ponds that hold water are built on sites with appropriate soil texture (percentages of sand/silt/clay). Clay content is especially important for the pond to seal correctly. A core trench is an essential component of the dam construction for the pond to seal well. The core trench is constructed early in the pond installation process. The trench is constructed by removing soil from the ground under where the dam will be placed until a good clay soil layer is encountered. Most core trenches are at least 4 feet deep. Clay soil is added back into the trench and packed down, preventing water from seeping under the dam after it is constructed. The lack of a core trench is one of the major reasons ponds leak. When a rock layer is encountered during pond construction, 6 inches or more of a high-clay content materials must pad the rock.
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Q.Does the soil at the pond site contain enough clay to seal well?
A.You can check the clay content by performing a ribbon test. Pick up a small handful of soil (the sample), wet it with water, and squeeze into a ball. Squeeze the soil through your fingers, rubbing your forefinger against your thumb. The soil should begin to form a ribbon. Do this several times with different samples. A soil with as little as 20% clay will form a 2-inch ribbon.
Measure the length of the ribbon and think about the feel of the soil. Gritty soil that produces a short ribbon may not seal correctly. Smooth textured soils, especially those that produce a ribbon longer than 2 inches, are more likely to seal correctly.
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Q.Can pond seepage losses be reduced?
A.Pond seepage is best improved during pond construction. Even soils with adequate clay content can contain small clumps that prevent good sealing (Table 3). Dispersants cause the clumps to dissolve and should be incorporated and compacted into 6-inch layers during construction. When renovating an existing pond, the pond should be drained, scarified, sealed with a sealant, then compacted. Sealing the pond after construction may not result in an acceptable improvement in sealing.
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Q.How compacted should a pond dam be?
A.Check compaction using a soil penetrometer, driving it into the soil at a rate of 1 inch per second. Compaction should be 625 pounds per square inch or more. For large dams, a hydraulic conductivity test may be necessary, send soil samples to a commercial lab to see how fast water can pass through the compacted soil.
