The sound of falling water is incredibly soothing--reason enough to install a waterfall in your yard in these stressful times. But a waterfall also has some other benefits. Falling water attracts birds, which are great for controlling insects in the yard and garden, and it increases local humidity so you can indulge ferns and other humidity lovers nearby. It also gives you the opportunity to diversify with aquatic plantings, and makes a restful place to enjoy them.
For a simple, natural waterfall, build two pools. Purchase a prefabricated double pool with an incorporated waterfall and follow manufacturer's instructions to install, or dig your own. Lay out both using a garden hose to outline each shape, making one higher than the other. Dig and level each excavation. Install a pool liner, overlapping the rubber or vinyl of the bottom pool with that of the top pool. Line with stones, plants, etc. and fill with water. Put in a recirculating pool pump to move water from the lower pool to the high pool, and enjoy as it tumbles back into the lower pool to start again. For detailed information, visit Perma-Culture's tutorial, "How to Build a Backyard Waterfall."
Set almost any odd bit of old farm machinery in a pool of water, run a length of plastic tubing invisibly up through it, and hide a pump in the base below it (submerged) and you have a quirky waterfall sculpture. An old well auger bit is a particularly inspired waterfall as the water follows the turnings of the "screw" from top to bottom with a pleasant rippling and bubbling sound until it reaches the pool below. Set a large brace (a specialized drill) bit in a saucer-shaped bird bath for a miniature version.
Build a pump waterfall for a bit of cottage charm. Old hand pumps are still available from suppliers to religious groups who eschew electricity or pick one up from a flea market. Use a recirculating pump (hidden in the bottom of a deep bucket, or watering trough) to pour an endless water stream into a container that never fills. Plant cottage flowers around it, and toss a flower-embellished straw hat---rakishly cocked to one side---on the top of the pump to complete the picture.
Use an antique grinding stone or pour your own faux version from concrete using a large round rubber feed bowl (available from farm supply stores) as a mold for cement. Fasten a pipe flange and short length of pipe to the bottom of the bowl and pour cement around it. It will resemble a big tube pan for Bundt cakes. When you have your "stone," place it in the center of your pool, propped on bricks (with the submersible pump hidden in the center and a short pipe length---just enough to come to the top of the center hole of the grinding stone---attached to the pump). With the stone a few inches above the water surface of the pool, the water will cascade gently across the stone and trickle down on all sides. Rounded stones, arranged artfully on top, complete this sophisticated effect.