First dig a BIG hole. The deeper the better, since deep water runs cool and is less likely to become stagnant or choked with algae (tiny green plants). Check local regulations, however. In Saskatoon, any pond deeper than 2 1/2 feet (76 centimetres) is a pool and must be surrounded by a six foot fence with locked gates. The large orange tarpaulin keeps the soil out of the grass and is also useful for covering the hole if it rains. If you are "lucky" enough to have clay sub soil, save some. It's perfect for planting water plants (fine and low in organic matter).
Ideally, your pond should have full sun all day, so water lilies will bloom. My local pond garden supplier recommends the "chain saw" solution, but I wanted to save all the trees, especially the "Rowan Tree" (Mountain Ash) which hangs over the pond a little. I planted a shade-loving lily, which cooperated by producing nice, pink on pink blossoms. (You'll note that your's truly did his digging in the morning, when the pond was shaded.)
My pond, "The Goldie Lochs", is styled after Loch Ness, in Scotland. (More about monsters later.) It has a small basin at the left and a long main basin, 3 1/2 feet deep. Shallower shelves were fashioned to support water lilies (2 - 2 1/2 feet deep) and bog plants (six to 12 inches or 15 to 30 cm deep). Water flows from a biological filter into the small basin and falls into the larger basin. The lay of the land favours this, since it is higher on the left of the photo.
The next step is to insert a heavy rectangular, plastic liner and fill it with water. The liner folds to fit the contours of the pond. The edge of the hole is dug so as to leave a shallow ledge for the edge of the liner.
The liner is then trimed with scissors and stones are used to hold it down and hide the edges.
The pond is planted a couple of days later, so that chlorine from the local tap water (which might hurt the plants) will evaporate. Follow your pond garden supplier's recommendations about the types of plants and their care. Our cats are convinced that the pond was built entirely for them, a private water hole and fishing reserve (they never manage to catch any). Its lovely to see them lean over with their shoulders hunched while they lap the water --just like the lions in Africa. This little monster is called Malcom (Calum Beg). He's about the friendliest cat I've met (to people), but he puts dogs and cats of all sizes, off the property with great dispatch. (This excludes our other two cats and dog, with which he is very friendly.)
(Closeup photo by Elise St. George, a neighbour and artist who usually paints in oils. If you think she takes lovely photos, you SHOULD she her paintings --magic!)
The scratches in the lily pad appeared one day when I was away. Several lily pads were ripped up. My theory is that one of the cats (guess who!), leaned over too far to try to catch a goldfish.