When trying to emulate a natural water feature, designers and contractors walk a fine line: The end result can't look like a masonry product, nor can it completely lack order. Success begins with the right rock choice and placement. Photo: Tumber and Associates In the entire universe of pools, spas, and water features, you'll find many installations built to evoke a natural lake, pond, or stream. But you'll rarely find a good one.

That's because many people believe that nature is random. When you hike up a mountain and find a stream, you may think there's no rhyme or reason to dictate how each rock is placed. While it's true that Mother Nature doesn't paint by the numbers, she does follow the simple rules of cause and effect: Smaller rocks break off larger ones, larger ones erode, and water takes the easiest path down a stream. Because of these things, you'll find that the stones are placed in certain ways.

Here are some basic rules to follow to boost the realism of your own rock water elements.

Choose weathered rocks. On your hike, you won't likely find stones that are shiny and new. So don't choose such specimens for your masterpiece.

On your trip to the stone yard or quarry, select rocks taken from the surface of a formation. These were exposed to the elements and have some discoloration and etching. Don't use quarried rocks that were chipped from below ground. Those will look brand new, with too-vivid coloration.

Mix them up. Mother Nature isn't a brick layer. It's hard to be convincing when all the stones you've chosen are, say, 1 foot in diameter. If you create a pile from these, it leaves the feeling of a stone wall or that you took a truckload of rock, dumped it in place, and grouted it as it fell.

Choose rocks of different sizes. Put the emphasis on larger specimens and let them anchor the waterscape. You want to avoid creating piles using a lot of small, baseball-sized pieces.

Don't place the stones uniformly. When it comes to rocks around the pond or pool perimeter, Japanese pond expert Doug Roth often speaks of the “necklace effect.” This refers to a single string of like-sized specimens placed in a straight line around the water feature, like a pearl necklace. Avoid this like the plague. Use different sizes and set them in a zig-zag pattern, with some creeping farther into the water than others. Go two or three stones deep every once in a while.

Provide a believable setting. Nothing says “manmade” more than a mound of rocks that spring up like a boil. Waterfalls don't erupt from the ground so create a convincing sense of context. If the back of the waterfall will be exposed, have it rise gradually from the back. Use plantings that are large and plentiful enough to conceal where the back of the waterfall meets the ground. If you're short on space, try planting large bushes or trees immediately behind the water feature. This makes viewers think that the water originated from far away.

Avoid flat weirs. Some designers will choose large, flat stones as waterfall weirs because they're the easiest to spill over. They require the least flow and create an impressive sheet. Some even go so far as to take a piece of flagstone that you'd normally use for a deck and incorporate it into a boulder fall.