DeerTexas,

I hope your photo is a test pit, rather than a pond. I have only seen "ponds" with those dimensions used for water storage for fire fighting, or irrigation recovery, etc. Even then, they were either excavated in impermeable clay or had an artificial liner installed. (As you said, there is no way to get material to stick to the sides of such a pit.)

Most typical ponds with "steep banks" are built with about a 3:1 slope - for every three feet you move horizontally, the pond bottom goes down one foot.

That is about the steepest that you can easily pack clay on a slope. (It can be done with steeper slopes, but you need better material, expert crews, etc. to work past the normal boundaries.) Further, some shallow water is good. That is the access for terrestrial wildlife, and the plant community in the shallow water is the start of the food chain for your aquatic wildlife.

The caliche is not a problem, IF you have good clay on location. You must cut and slope back any caliche layers and cover with a compacted clay blanket. A 12' deep pond would probably need about 18" of clay on the bottom and up the side slopes. It needs to watered to the correct moisture content and compacted in 6" lifts.

If you can see horizontal layers in the topography of your property, AND your pond location is in the same "layer" as your neighbors', then your subsoils will probably be similar. However, if you are in a different layer, then you could have quite different materials. Further, a modern caliche layer can be developed based upon the groundwater level and the level of the roots of your cover vegetation. It can therefore cut right across geologic layers in certain conditions.

You definitely need to excavate some test pits in your preferred pond location. You can wet some of your material and see if you can make a cohesive golf ball with some of the stuff you think might be clay. If so, find your best layers and send some of that off to the soil lab to determine the clay content. (Frequently called a "grain size analysis".)

If you do NOT have good clay, and have lots of hard caliche, I believe it will be difficult to seal your pond even with bentonite. The caliche may exhibit large pores and fractures that are very difficult to seal. In that case, you might need to install an artificial liner.

Finally, the size of the pond is not the sole controlling factor to avoid going dry during droughts. The pond actually needs to be "right sized" for the watershed area that drains into the pond combined with the annual rainfall amount. (That is only the first approximation. The slope of the land, cover vegetation, soil type and permeability, and several other factors are also important.) If your pond is too small for your drainage area, then a big rain can blow out your dam. If your pond is too large, then it will only be full during the peak of the rainy season, and will be low or dry during drought periods.

I hope that helps with a few more items for you to evaluate.

Good luck with your new pond project!