I want to make a large pond in my yard. How can I make it hold water?

https://modernfarmer.com/2015/07/how-to-make-a-pond/

Try this site: https://www.popularmechanics.com/home/outdoor-projects/how-to/a661/2770526/. I have a pond in my back yard and I absolutely love it, good luck and have fun building it.

You need a pond liner. Found at any pool and pond store. Some larger nurseries carry pond supplies.

You need to purchase a heavy plastic liner to hold the water.

My 1800 gallon pond was dug out and shaped by me, and all the plumbing was installed. Then a fiberglass fabricator came in and lined everything with fiberglass. No leaks after almost 30 years!

browse through others projects....https://www.hometalk.com/categories/outdoor-living/ponds-water-features/ponds

There are liners you can get for that, either a formed plastic one, of you can dig it to the shape you want and use a rubber lining fabric.

By using a Butyl Liner. I would suggest you buy a Magazine on building a pond, or buy a book on the subject or maybe borrow from a Library, as you will need to keep referring to it as the project progresses.

You have to line the whole bottom of the hole with a rubber lining made for ponds. Or you could also use a pool liner.