I'd like to create a pond in a wet spot in my yard so that I can plant some beneficial water plants and possibly attract frogs and toads to help control pests. Is it possible to seal the pond so that it consistently and naturally holds water with out using a plastic pond liner or something like conrete? Ideally I'd like shore plants to be able to get their roots into the water.
Sepp Holzer seals ponds without using liners. Check out this video [which has pretty bad audio].
Summary of the technique (I haven't tried this, but I would expect that the devil is in the details...):
- dig out the pond
- while water is in the pond, compact the bottom -- he talks about using an excavator or backhoe with a vibrating attachment
- if the soil is rocky/gravelly, you need to remove extra soil to get rid of the rocks, then replace it with finer soil that will compact better
- it may require multiple compactions
Clay. Cheap, simple, abundant. Any soil with a clay content in excess of 40% makes a darn good water retention layer. One dump truck load of locally sourced high clay should be all you need.
See "Water Content‐Density Criteria for Compacted Soil Liners.” in the Journal of Geotechnical Engineering, Volume 116, Issue 12 (December 1990) by D. Daniel, ASCE. and C. Benson, ASCE.
You can seal a pond by putting pigs in it. They'll compact the bottom so much that it stops leaking. It may take a few years though. See http://www.makeitmissoula.com/2012/07/paul-wheaton-can-pigs-build-ponds/