Here the state has experts who will come out for free to evaluate pond sites to tell you if it will hold water, for instance. They call them the conservation experts or something like that, through the farm service, I think.
If a pond is leaky the old wisdom is to pen pigs there to dig in the mud and compact it all down. I've never tried it but mine can make a shallow wallow hold water longer than I'd think possible.
You want your pond at least 7 feet deep to protect fish from cranes. It also helps them regulate their temperature, and keeps weeds from taking over.
Shade is good over a pond, if you want to plant some weeping willow, be sure to do it on the side away from the dam, since folks here have told me the
roots can open up leaks. You can get them for free - just find one you can get some cuttings from once it's dormant - pencil-thickness will do, and stick them in the soil, or you can pot them and water them and they'll start growing in a few weeks (more fun for the kids). Plant them outside when you see the other willows growing leaves.
You can pick up some watercress in the grocery store and throw it in your pond and it should just start growing there, ready for you to harvest for salads and stir-fries. Elderberries like to grow where it's wet, so maybe you could plant some of them wherever you find water seeping out below the pond.
Some pretty awesome wildlife will find your pond all by themselves. They say in Kentucky almost every pond gets a snapping turtle. Frogs and toads breed in them, and then leave to eat slugs and bugs all year for you. Also dragonflies and damselflies breed there. The adults are predators that eat hundreds of mosquitoes every day plus other insect pests. Water draws wildlife to come drink - I see footprints around my pond from raccoons, possums, and cranes. Even box turtles like to drink out of a pond.
If the pond currently has no fish, get some minnows like they
sell for fish bait to put in there. They'll breed freely and eat any mosquito larvae that try to grow there. If you decide later to put in some bass or sunfish, they can eat the minnows.
Bamboo can become invasive, I'd be very cautious about planting some.