When we dug our tank the guy who dug it said well I got good and bad news... This clay you have will hold water like a cup, but it only runs 6-7 foot deep.

Our tank is 5 foot in the middle and it does hold water really well, but its to shallow and small to make it through big droubts and it has to rain over 2 inches most of the time to generate enough run off for it to catch something.

thats a big pond

No clay, all calichie. It probably won't ever hold water very well. A tank liner is about the only way it will work unless you can have clay hauled in.
We have dug about 30 tanks and if we don't find good clay we just fill them back in and move on.
Before you build the next one get a backhoe out and dig some test holes to see if there is clay.

I would have cut a core trench if possible and filled it with clay. There is good clay in some Hill Country counties. Look for old seeps or springs and that is a good place to start for a new build or getting clay.

My brother has spent the last ten years working on our biggest tank. It's deep, but barely holds. A couple of smaller ponds hold well. It's the darn Caliche. Need to get a liner IMO.

I am doing my part to conserve our natural resourses. I am building as many recharge dams as I can. Out of 12 built so far 3 hold water. Good thing I am not doing this for a living. On this one I cored it about 8' deep. This was a few years ago when it used to rain. A spring started flowing and filled up my core. It stayed like that for a few months. I tried pumping it out but it would fill back up over night. I know it will never hold but I was just wondering how deep the old creek was originally. One of these days if it ever gets back to normal it will be a heck of a swimming hole when the spring flows again.