Pond leaks can spring for a number of reasons, including natural occurrences, the age of outlet pipe or drain structures, or even inadequate construction. The best way to avoid a leaky pond is to properly build one from the start, but even a well-constructed pond may develop leaks as it ages. Some newly constructed ponds can appear to leak severely just after construction, but this is likely due to the soil needing time to completely saturate and swell to seal against leaking.
Tree roots, ground shifting, or critters that dig into the banks or dam can also cause problems. Most of these leaks can be prevented with proper maintenance, though some things can go unnoticed. If you see a small drop in the water level it may not indicate a leak at all. Evaporation and seepage can result in a slight drop, especially in warmer climates. During the warmer months and in times of lower humidity, a pond may lose over a quarter of an inch of water in a day. If the pond doesn’t have a continuous water supply, this can be noticeable over time. Water losses over 12 inches may indicate a leak, however, and should be investigated. During droughts, the water level may drop significantly and the exposed sides may crack as they dry out, leaving them vulnerable to leaks when the pond refills.