Spring fed pond/natural pool

Hello!

We have a bit of a unique water set on our property and I’m hoping to get some advice on how to harness it.

Our property sits in the inside walls of a small valley, with a spring running down into the lowest spot, and the house is up kind of built into the side of the southeast facing hill. The previous owner had run a hose system up from the spring so she could water gardens and such with the spring water. So, when we got here there was a hose dumping out a constant flow of water, year round, into the yard. Needless to say we were excited to find a more effective system.

Now, we’re wanting to build a relatively small pond that will feed out into some raised beds and then eventually into a drip irrigation system for a tree grove down hill further. We also have dug it out big enough so that we can sit in it in the summer when it’s hot. Okay, Done with background.

So I’ve been trying to avoid using a plastic liner, but so far what I’ve heard as an alternative to that is bentonite clay, which would be far above our budget. I’ve been thinking that our soil has enough of a clay content (just a guess from looking at it) that we could get away with puzzle piecing big flat rocks on all the surfaces since we’ve got quite a few sitting around. Maybe filling in the spaces with gravel would be enough to keep it from draining out? Or maybe we could just fill in the spaces of the rocks with b. clay so we don’t have to buy so much of it? My partner doesn’t think it’s worth the risk of going through all of that work and having it fail. I don’t disagree.

Next question, since the pond would be fed a continuous flow of clean water, would we have to worry much about gunk building up on the rocks? I know oxygen is important, and multiple depths, and plants, so we have all of that built into the design, but is all of this enough?

Here are some pictures:

personally, I would think with a constant water supply coming in, you will get some kind of pond, liner or not.

Just let the water run in, and see how well the existing soil holds water and for how long.   If not enough,
then stop the ingress of water, let the hole dry up and try a liner or clay.

As for "gunk" you're not generally going to get algae or other build up if the water is moving and not stagnant.
Some buildup of natural algae, mosses, water plants is natural of course.

The rocks you described will still leak water.
But they might be nice to sit on instead of the clay.
Running water as suggested will not become dirty water.

Maybe plant appropriate reads and plants aroind, to replicate a natural pond and establish a spillway that will not erode away.
Could be very nice in summer.

Personally I would dig out your area and if it is as you say clay like material then I would tamp the earth with a handmade wood tamp.
Or you could buy a metal tamp. That will compress the soil and create a natural bed capable of holding water long term. If once you try tamping and the bed of your pond still seems porous or brittle you would need to add something like clay, which you could find and dig up and transport to your pond. Mix clay in with your existing dirt and create a compressible layer. Then tamp that down. If hand tamping is not your thing you can rent a wacker packer, fire it up and bang it around your pond.
If that doesn't hold water still you could buy some cement mix and add it to your material. Cheaper than that fancy stuff you were mentioning.
Really it boils down to budget in the end. How much you want to spend versus how much labor you are willing to expend.
Good luck!