Pond and Lake Leak Location and Repair
Perhaps nothing is more frustrating that finally constructing the pond or lake of a lifetime only to find that it doesn’t hold water. Just as frustrating are repairs and repair theories that do not hold water.
We will focus our leak location and repair strategies in 2 main areas – 1) SYNTHETIC LINED BASINS from small garden ponds to multiple acre ponds and lakes. 2) NATURALLY LINED BASINS – can be excavated ponds or lakes with no dam embankment or a pond or dam excavation Mornington peninsula lake constructed with a dam.
First things first – how do you locate the leak? This can be exceptionally simple or painfully difficult depending on the situation. Let’s state the obvious and move on from there – look for the wet spots around the pond. A soil probe will allow you to find moisture below the surface. If you do not have access to a soil probe, a ditch shovel will work just fine. Probe or Dig as deep as you can in the suspect area and examine the soil for moisture content. The best time to look for moist areas around the pond is after an extended dry period – preferably a week or more. If you find significant moisture, you are likely in the vicinity of the leak and can narrow your search. Pay attention to vegetation around the pond. Lush green vegetation during extended dry periods can help you narrow the search as well.
Once you’ve narrowed the search or if you just can’t narrow the search, allow the pond water surface to fall without replenishing the water until the water level stabilizes. Mark this level and investigate the pond around this elevation. For a synthetic liner pond, you have found the elevation of the leak, careful inspection of the liner at this elevation should allow you to find the leak.
If you have an EPDM rubber liner (Firestone Pondgard or similar) the repair is quite simple once you’ve found the leak. Purchase an inexpensive EPDM Repair Kit and apply per the instructions. If this is the only leak in your pond, you may refill and enjoy!
If the pond is a natural bottom or unlined pond, the search becomes a little more complex. As with the lined pond, it is worth examining the pond at the elevation where the water level stabilized. There are 2 reasons that the water level may have stabilized at this level. One, this is the elevation of the leak or two, this is the natural groundwater elevation (water table). A simple pump test will determine with reasonable certainty whether or not the pond bottom has intercepted and is connected to the water table.
To accomplish the pump test, select a pump that will allow you to draw down approximately 6 inches of water from the pond surface in less than 3 hours. Mark the starting water surface elevation and ending water surface elevation. Over the next 6-8 hours monitor the water surface carefully. If the water surface rebounds toward the starting point, the pond has most likely intercepted the water table. If the water surface stays at the same elevation, the initial water surface elevation is the elevation of the leak.