Irrigation companies here use it in the canals when they've got a leak. The companies will drop the level of the canal (reduce flow) and sprinkle bentonite liberally. Let settle then resume the previous flow.   It does work.

If all else failsl,, get the pond level down and find the stickiest, heaviest, gumbo clay you can and spread 3-4 inches deep in bottom of pond. Don't have to drain pond just get it down so the hoe operator can "sorta see" where the clay is dropped set in and smear it around.

Course depends on size of pond.. :-)

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