There are many reasons for the water table in a pond to drop. Possible causes should be considered -- such as high water use from neighboring vegetation like willow trees, excessive evaporation due to high temperatures, or drought conditions resulting from low rainfall -- before determining that the culprit is a leak. Walking around the berm and dam of a pond to look for soggy areas can help diagnose if seepage is what is lowering the water level. However, sometimes the only visible sign of a leak is a pond that will not hold water.
Things You'll Need
- Pump and hose
- Excavator or tractor with a bucket and disk or rake attachment
- Powdered bentonite clay: 1 to 3 lbs. per square foot
- Sheepsfoot roller
- Mulch hay
Drain the pond fully using the pump and hose and allow the soil to dry until optimum compaction moisture is achieved. Soil compaction can be determined by pressing a handful of soil into a ball. If the soil crumbles, it is too dry. If water leaks out of the ball, it is too wet.
Clear the pond area of all trees and stumps filling any holes. Disk or rake the top 8 to 10 inches of soil, removing any rocks or tree roots that are disturbed during this process.
Apply powdered bentonite over the soil surface at a rate of 1 to 3 lbs. per square foot. Coarse soil should receive the heaviest application rates.
Disk in the bentonite clay to a depth of 6 inches, again removing any rocks or tree roots.
Compact the soil under proper moisture conditions using the sheepsfoot roller. Four to six passes of the roller should be sufficient to compact the soil to a depth of 8 inches, which is sufficient for a water depth of 10 feet. If the pond water depth is greater than 10 feet, soil may need to be compacted in layers to achieve a compaction of 8 inches per layer with two or more layers.
Protect treated areas from drying by mulching with hay during the final compaction stage.
Fill the pond. Bentonite will swell from eight to 20 times its original volume to seal pores between soil particles.
Tips & Warnings
- Bentonite will shrink and crack when dry, so it is not recommended for ponds in which the water level will fluctuate widely through draining or excessive evaporation.
- Bentonite can be expensive. Treatment efforts can be concentrated around suspected problem areas, rather than the entire pond.
- Using heavy equipment on ponds with steep sides is not recommended due to the danger of tipping.
- "Alabama Cooperative Extension System"; Pond Building: A Guide to Planning, Construction, and Maintaining Recreational Ponds; Chris Hyde and Perry Oakes, August, 1998
- Penn State Cooperative Extension: NRCS Pond Construction Manual
- Photo Credit Jupiterimages/Photos.com/Getty Images
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