Once you’re satisfied with the placement of your stream and waterfalls, lay down some cushioning underlayment (if necessary) and fit the liner to the entire excavation site. Try using a single piece of liner for the most problem-free design possible. If you must use more than one section of liner, make sure that you start at the lowest end of the stream and overlap the pieces on your way up. Lap each upper section over the lower piece and seal the seams with adhesive or tape made for use with pond liner. (Make sure the liner sections are dry before attempting to seal them.) Sealing will allow the water to flow over the seams without any leakage.

As a rule of thumb, overlap the liner for the stream bed by 6 – 12 inches on each side. That will leave you enough extra material to work with should your trial run show that you need to make some adjustments to the height of the banks or the sweep of the curves.

Taking a Trial Run
After laying out the liner, sealing the seams, and making sure that everything is in place, set your pump into the lowest part of your pond. Place it on bricks or on a flat rock so that it won’t take in silt from the pond’s bottom. Attach the pump to the supply and outlet lines, and fire it up.

The pump will quickly begin moving the water to the top of your stream bed, where it will begin running downhill, filling up the stream and any pools or deeper pockets along the way. If the water gets too close to the top edge of the liner at any location, build up the bank at that point with rocks, stones, or soil. Remember that nature will provide for some settlement over the course of time: you don’t want the settling to be on the banks, where water could escape your system.

This is a good time, too, to check out your falls and spillways. Make adjustments in the rocks, and be sure that the water going over the falls remains inside the liner. (Waterfalls have a nasty habit of wanting to allow water to sneak out over the liner's lip.)

At this point, you’re going to be tempted to trim off the excess pond liner on each side of the stream. Don’t do it. Instead, begin disguising the liner by folding the excess under and covering with soil, rocks, plantings, and any other landscape or hardscape elements you wish. You can always come back and trim away the excess afterwards. Remember: it’s easy to cut away; it’s a lot more difficult to replace!

Gravel, Stones and Rocks
Once you’re satisfied that your stream is functioning properly, finish laying rocks along the outer banks. These rocks, called edging, will help hold the liner in place while disguising its presence. They will also help create an optical transition from the stream bed to the surrounding landscape.

Edging stones can be flat or round, laid in one course or stacked, depending upon your personal tastes. Although we prefer to use free-standing stones so that they can be moved around whenever desired, you can also set stones in mortar, should you so wish. Mortar prevents water from flowing under and around the edging and softens the sound of the flowing water. Make sure that you rinse away any excess mortar and drain the pond completely of all sediment before adding fish. Uncured mortar is toxic. Always wait at least one week before adding fish to a water feature containing freshly cured concrete.

If you want to give your waterfall a spillway (a series of flat, stacked rocks over which the water from the falls flows), begin laying the rocks from the bottom up. Leave a few overlapping rocks for the water to spill from one level to the next. Tilting the spillway stones slightly forward will keep the water moving toward the stream bed and increase the volume over the face of the spillway.


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