This is the iconoclastic artist in me sprouting fresh and strange ideas as I learn to think in the medium of plants and earthworks.
Or maybe this is really old hat to the permies here. I'm relatively new to this scene, so I still think all my ideas have never been thought of before
I'm willing to have my hat handed to me. I just want to learn and grow.
I have been making plans to permacize a low and (relatively) wet depression on my land by berming up the side just before it flows onto my neighbor's property.
Flows, that is, during torrential rains when the water runs faster than it can soak in. That happens maybe 2 or 3 times a year, and only in this one spot.
But it can become quite a large pond for short periods.
Anyway, I love the idea of ponds, especially the ability they have to moderate temperatures, create heat traps, and intensify the solar effect during cooler seasons by reflecting light, ala the mighty Sepp, but I _hate_ the idea of accumulating water in one location only to watch it evaporate.
So, has anyone tried this?
Dig out your pond and seal it somehow just as an ordinary pond, probably with a bioplastic glee, then, while it's still moist, and after some testing of course, fill the damn thing up with sand.
Yes, that sacrifices the option for fish and the beauty of a natural pond with water, BUT... that doesn't seem very practical in my location. in exchange for this trade off I'd get...
1. massively improved evaporation deterrence (Molllison has touted sand as a way to basically eliminate evaporation)
2. no mosquito breeding ground
3. the additional density for thermal storage and temperature moderation is probably close to that of a regular pond.
4. solar reflection off of the light level surface would offer very similar benefits of a regular pond.
5. Plants grown around it can still take advantage of the extra moisture.
6. Water still has the potential to exceed the sand level and provide a periodic accessible water resource for animals and birds.
So, now someone will come along and bust my bubble and tell me, "oh yeah, that's known as a so and so ... and has been practiced by la la la... for more than badaba... "
But that's ok. If one has a bubble at all, I believe it's the civic duty of the community to bust it with extreme prejudice.
After all, enabling misguided ignoramuses is so last century.
I'd love to know if this has been done under any other name and what the real world results and issues are.
And if it hasn't been done, what do you think?
Would hate to find out after buying that much sand that there are hidden gotchas that aren't obvious.
Here are some results from a search for "groundwater dams":
There were many more hits that you might find helpful, so I recommend you also do your own search.
I think that the primary benefit, other than reducing evaporation losses, is circumventing rainwater storage restrictions (though one could argue, because it is sealed, it is a type of underground storage).
Andrew Parker wrote:What you propose is not a groundwater dam, but it is similar, perhaps more like a sand dam (but still different) -- but you are supplying the sand. The key to it working will be sealing the "pond". Clay might do the trick, or you could also try a synthetic liner. If it holds a lot of water for a long time, you might have problems with burrowing animals puncturing the seal.
Will burrowing animals dig through wet sand and dig deep under a heavy moist pond?
not doubting, just checking. Most of the burrowing animals around here seem to like drier hovels, but then again I don't know much about what they are given to do.
I think I'd be surprised to see them do that. (or, maybe I'd never see it).
Seems like they'd be asking for trouble.
We get rabbits and a few prairie dogs, but the cats mostly keep them at a distance.
We don't have rainwater storage restrictions here. At least not yet.
I really like the heat traps and microclimates Holzer makes, but I can't see an open faced pond being around permanently in my climate, so I was thinking the sand could allow me to have that functionality in a much drier climate. The water is nice when it comes, and when it comes it will stick around in the sand, but it isn't even strictly necessary to serve many of the heat trap functions of a pond. The sand alone could serve that role to 75% efficiency I'd guess when the water is very low.
Still kicking it around.
Thanks for the links.
lots of folks dig a hole, and fill it with rocks to store rainwater in the desert, and as flood control in the city.
havnt' heard of anyone covering with sand, but should work, you just lose the surface area for planting, and that makes it warm quicker.
there was an architect that dug a small pond, deep, and then put a metal frame over it, lay a couple layers of sandstone slabs over the metal, and put a fountain in the center.
only evaporated about a cup a week, and the birds loved it.
he also used it as an outdoor shower.