The great variability of natural streams cannot be duplicated in a garden stream, but is a useful ideal to keep in mind. The more it is part of our conception, the more attractive and interesting the stream will turn out to be. We are not talking here about copying nature, which we could not do if we tried, but about being aware of the many different features that make up a stream. One thing to strive for, for example, is to construct the stream bed and banks differently in the different sections. Widenings and bends, a marshy strip several feet wide alongside the stream, a series of small dams, rocks and pebbles in the stream bed, and varying water levels all enliven the water and affect its speed. In bays and behind rocks and roots the water comes to rest, and it is especially these quiet pools that are favored by plants and animals that live in and along streams.
Planning the Stream’s Course
Paper and pencil and a long garden hose or rope are just as essential in the planning of a stream as they are for designing a pool.
The Stream’s Length: If the stream is to double as a biological filter the rule of thumb is to figure on 5 feet (1.5 m) of stream per 250 gallons (1,000 L) of pool water. To give an example: Since a pool of 60 square feet (6 m2) holds about 1,000 gallons (4,000 L), a stream connected to it should be about 20 feet (6 m) long.
Length is of less importance in a stream that is not connected to a pool. But it should not be too short, or the water will not flow properly. Figure on a minimum of at least 15 feet (5 m).
The Stream’s Course: Your stream will most likely end up longer than the minimum given here. This is because once you start marking the stream’s course you will find that even a small garden will accommodate quite a long stream. Run it along the fence, incorporate some S-curves around trees, or have it meander in wide oxbows across the lawn. Experiment with the garden hose, a long rope, or both. You will be amazed at how many feet you will lay down without it seeming to be too much.
Width and Depth of the Stream Bed: Use your spade as a measuring stick. An ideal average size for a stream bed is 1 spade’s length deep (about 10 inches or 25 cm) and 2 spades’ lengths wide (about 20 inches or 50 cm). These dimensions will work in any garden. Wider streams are suitable only for large gardens because the curves take up a lot of space. Narrower streams of about 12 inches (30 cm) are still functional, but if they get narrower than that, they become mere rivulets through which the water can be moved only with difficulty. The dimensions indicated are meant merely as guidelines.
Although the water in a garden stream is driven by a pump, its liveliness and the desired leisurely speed are the result of several features:
– Varied water depths¡ªdig the stream bed to different depths or add varying amounts of fill in different spots when you first set up the stream’s course.
– Obstacles in the stream bed¡ªadd rocks.
– Narrow channels¡ªplace rocks or containers with plants in the water along both banks.
– Bulges in the stream bed¡ªarrange small or larger marshy areas or bays (minipools) at least 3 feet (1 m) wide here and there along the stream bed.