Once you have a garden pond, you're probably going to want to build a waterfall in it. After all, what looks any nicer than cascades of sparkling water falling over the rocks or sounds any more natural? In addition to looking and sounding lovely, a waterfall is also very functional in circulating water and allowing it to oxygenate which enables your fish to breathe well. Although you may be thinking that your yard is too flat to support a waterfall feature, you'll find that it's simple enough to build one yourself, and the waterfall you create will greatly add to the atmosphere you've developed in your yard.
While creating a stream will only require a drop of 1" per ten feet, you will need considerably more drop for a waterfall. If you have extra soil left from digging your pond, you can use it to create a natural landscape that has fall. By all means, don't just pile the dirt in an unsightly hump. Level and blend the soil into gradual dips and falls. If you're lucky enough to have a yard with natural slopes, you can take advantage of it by building a series of ponds with waterfalls flowing into each of them them. If you do this, take care that the top pond holds the least water and the lowest pond holds the most. If you don't have the natural fall, you might want to buy a fiberglass insert that will "mold" your landscape for you.
Be sure to build your waterfall with sides that are high enough to keep your water from splashing out. You will also need to line the sides so that the water doesn't just soak away into the ground. When you build a waterfall you will create a pumping system to recycle water back up to the top of your falls. While some of your water will evaporate as you might expect, you can slow the decrease in water flow by taking these preventive measures. If you can afford to have water piped to your water garden, this won't be a problem for you. Otherwise, you need to be prepared to add water to your pond on at least a weekly basis. Use rocks to keep your liners in place and to provide a natural-looking setting for your water garden.
There is a lot of planning that goes into building a great waterfall, but if you use the techniques and methods you'll find on the Internet, you can successfully add a waterfall to your water garden and make your yard the showplace of the neighborhood.