You don't need water to suggest its presence in the garden. Just build a dry creek bed that looks as though a rushing stream deposited the stones and settled them in. The bed we saw took two people only four hours (including shopping time) to complete, and cost under $300. It measures 17 feet long and widens from 1 foot to 5 feet; it's 1 inch deep at the sides and 3 inches at center.
To build one like it, you'll need 1 roll of landscape fabric; 6 boulders ranging from 1 to 2 feet across; gray cobblestones (about 4 cubic feet each of three sizes, 1 to 3 inches in diameter); and about a quarter ton of 1/2-inch gray-toned and sand-colored pebbles.
DESIGN: Gay Bonorden Gray, Mountain View, CA (650/969-9523)