There are many reasons to add a waterfall. Waterfalls are beautiful to look at and the moving water adds sparkle to your pond. Waterfalls sound good, they provide a way of recycling the water and they also add valuable oxygen to the water to benefit fish. Waterfalls or moving water create white noise. White noise helps screen out unwanted sounds of the world beyond your garden. Creating a waterfall takes considerably more planning than other water features such as, fountains. You do not need a natural hillside for a waterfall or stream. The dirt you had left over after you dug out your pond can be used to buildup your waterfall. Do not pile the dirt in one spot. Blend it in around your pond to naturalize your landscape. You can also use fiberglass inserts with spillways. If you have a sloping site, a series of waterfalls can be connected to several small ponds making a dramatic ribbon of water.
To recycle water to the top of your falls, the bottom pond (reservoir pond) will have a pump connected to tubing that will run water to the top of your falls. Always make the bottom pond larger than the top pond. The volume of water needed to cause the top pond to overflow will not lower the water in the bottom pond to a point that it does not look good when the pump starts.
Every waterfall or stream must be lined to prevent water loss. The sides of your falls must be high enough to prevent water from splashing out. There will be some evaporation of water and you may need to add or “top off”your pond weekly. You can use a single piece of liner for your pond and falls but this could be awkward to work with. If you use a separate piece of liner for your falls or stream, you must overlap the upper level liner over the next level by several inches. The width of the water course needs to narrow where you plan to have it go over the falls. Rocks will help hold the liner in place. Put stones in the narrow area and use flat rocks on top of them. Your flatrock (spillstone) should slope slightly toward the lower pond and project over the foundation stones directing the water out rather than down. This will make a nice sound as it spills into the lower pond. Bring your liner up the sides of the water channel as least 12 inches. Tuck the liner back into the soil and hide it with rocks. Run water to test the flow of the falls. After you are pleased with the results, you can mortar the stones into place on top of the liner as you would to install edging.
If you are using mortar or concrete as a base of your waterfall or stream, you might be inviting leaks. Michigan’s climate has an alternating freeze-thaw. If you do use mortar to finish your construction, either scrub it down with vinegar water and rinse many times, or run water through the system for a long time until the water pH in your reservoir pond tests below 8.5 before you add any fish. A well-placed liner under the entire structure will prevent leaks and loss of water. Many pond builders use waterproof spray poly foam to fill in behind the rocks to prevent water loss. Poly foam comes in a pressurized can with a narrow tube. This was used on my falls but it turned yellow after one season, and did not hold the rocks into place any longer. I had to redo everything. Maybe there is new and improved foam that will not do this. I have not heard of any as of yet.
Streams can be set in level ground. A stream only needs a one-inch drop in elevation per ten feet to affect a flow from the top down to the reservoir. When you are digging out your stream, dig deep enough to allow for the thickness of all the rocks and up to three inches of water and 3-4 inches above that. Dig your channel wide enough to accommodate the widest section of your stream. Use one piece of liner for your entire stream bed making sure you overlap it by several inches into your reservoir. I would recommend using a double-sided tape and a special adhesive to hold your pieces together. You will need to dry this with very high heat. A hair dryer does not get hot enough to give a permanent fixing. Use a professional heat dryer. You will also need a strong enough flow to create the look you will want. Small pebbles will create a rippling affect. You can support the edge of your stream with a concrete form or board. My stream was built without any support. Every time you stepped close to the edge it slowly caved in making the stream smaller and smaller. The best solution to this problem I’ve seen was to use sand bags on the edge and bring your liner up and over them and tuck it under. Then you can place rocks or mulch right up to the stream without having it cave in.
You can set streams in circles around your trees but use an underlayment of specially treated landscape cloth that repels tree root invasion. Streams can be made to connect one pond to another. Keep streams and falls natural by using different sizes of rocks. Always set your side rocks in first because these will be your larger rocks. Rocks rarely sit fully on top of the ground. Use a pump that will pump the volume of water you want. A small pump will only send a drizzle of water over your falls or down your stream.
Safely tips: Rocks that are in your pond, stream and waterfalls become extremely slippery. Do not climb or walk up your falls. Rocks can come loose and tumble down if they are not secured.
Darlene Jennings (pond Lady) President, Mid-Michigan Pond & Water Garden Club Advanced MSU Master Gardener