I have this reservoir, located in an all-stone wedge in the terrain. The water is held back by a small dam, consisting of granite boulders held together by a mortar.

dam wall

As is evident from the water level, it's not doing its job very well.

How would I go about waterproofing it?

A great number of compounds and membranes seems to exist, of which I do not know the efficiency, but keeping the water food grade seems to limit the options considerably.

Another idea is to just pile up peat, which I have in great supply, in front, but that would be a waste of time if any actual solution would require removing it again first.

  • I have no experience whatsoever about building dams. But beavers do it without mortar all the time. :) And the water is still drinkable. Maybe some wildlife research might provide a decent water-safe solution. Commented Jan 1, 2022 at 14:20
  • 1
    Don't drink from beaver ponds. It's not the dam materials (sticks and mud,) it's the parasites in the beavers, in the water, and then in you...
    – Ecnerwal
    Commented Jan 1, 2022 at 14:39

1 Answer 1


Plenty of water stored in cement tanks, so a better job of mortaring should do.

Bentonite clay is a different approach, commonly used to seal around drinking water wells and to seal ponds, etc.

Stock treatment of a drinking water pool of this sort would also be to cover it to prevent insects and animals/leaves from fouling it.


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