The location of your pond should be decided. You've picked a good spot in your yard where you can see the pond from different places, and it's near enough to the house so you can see it from a window. This is really part of the fun because you can visualize the landscaping ideas you'll be incorporating into the pond area once the dig is finished.
The first thing to do is outline the perimeter of your pond. Avoid square or sharp corners because your pond liner will conform much better to a freeform round or kidney shape. You should also have made the decision by this time about the size of the design. I would strongly suggest not going too small. I changed the size of our pond two times because the first and second time just weren't big enough. Lay out the final design and size on the ground where you plan to dig with a can of spray paint.
The next thing to decide is the depth of the pond. I would suggest at least twenty four to thirty six inches. Our pond is thirty six to forty eight inches deep and the main reason is the fact that we have fish. Some of our fish are quite large, we have two Koi's that are about eighteen inches long and they definitely need the room. If you're going to have fish, or think you might get fish in the future, then don't skimp on pond depth. If you live in a cold winter climate like we do, then the fish need room at the bottom to winter over. Like I mentioned previously, we haven't lost a fish to the winter in the eight years we've had our pond.
Keep in mind that you want to keep the top 'shoreline" edges pretty level. The reason for this is that once you put the liner in and fill the pond with water you won't have a large piece of the liner showing on the high side of the hole. Also as you dig, remember that you are going to want a ledge most of the way around the perimeter of the hole, about six to twelve inches down from the top and about twelve inches wide. This will provide you with a "shelf" to set your pond plants on.
Once the hole is dug and shaped to your satisfaction and with any protruding sharp rocks removed to provide a relatively smooth surface for the liner to rest on, then you are ready to install the liner. Here are the quick calculations to figure the size of your liner:
Length: Length of the dug out area plus two feet plus the depth plus three feet.
Width: Width of the dug out area plus two feet plus the depth plus three feet.
For Example: The hole is ten feet long by six feet wide and the depth is three feet. Therefore, the liner LENGTH is 10 + 2 +3 +3 = 18 feet. And the WIDTH is 6 + 2 +3 + 3 = 14 feet. So the needed liner size is 18 feet long and 14 feet wide.
Some people have lined the dug hole with old carpet scraps to provide a little extra cushion under the liner and also a little more protection in case a sharp rock may have escaped detection. Personally, I didn't do this and we haven't had any leakage problems.
So, now it's time to install the liner. Make it easier and get some help for this operation. Position the liner over the hole, trying to keep an even overlap on all four sides. Next push the liner down into the hole as evenly as you can, keeping in mind that you want the overlap to be as equal as possible all the way around the hole. When you are satisfied that the liner is positioned correctly, place a few heavy rocks on the overlap equally spaced around the pond.
Now it's time to start filling the pond. Obviously, the smaller the pond, the quicker the fill. A large pond can take quite a while, and while it is filling use the time to disperse the liner evenly so that you don't get a lot of large folds. You're bound to get some folds but if you work on smoothing them out as the water is going in the end result will be a nicer appearance. If you have to make any moves to even out the overlap, do it before too much water is added because it gets heavy fairly quickly and once the weight of the water takes over you won't be moving anything. As the pond fills and the liner conforms to the shape of the hole and you see that your overlap around the edges is looking pretty good, then you can start to relax because the hard part is done.
Robert Dorrance has had a pond for the last eight years and would like to share his experiences with you. You can read other articles and download my free e-book, "How To Build A Beautiful Backyard Pond at http://www.Backyard-Pond-Guide.com