To build a backyard water feature, create a design plan with a budget, style, size and placement in mind before purchasing any materials. Once the materials are purchased, mark the area, and dig up the soil to suit the depth of the pond or liner. Fill the hole with sand to protect the liner from sharp rocks or debris. Fill the liner with water, and add decorative plants or materials around the water.
If the water feature is particularly large, you need to budget for equipment to dig a deeper hole and other considerations, such as extra labor and maintenance. Use sand to outline the boundaries of the water feature to make digging the area easier. Once the hole is leveled and protected with sand, place the preformed mold or liner into the hole and fix any areas where the liner does not fit properly. Use marginal plants, rocks, slate, bricks and other material to decorate the water feature. Buy materials that suit the size of the feature.
Add outdoor lighting around the decor for use at night. Consider adding a fountain, waterfall or fish, but plan for power source access for water filters and UV lights. If necessary, use conduits, and bury them in a trench in the ground leading up to the water feature. Install any fountains, waterfall or filters according to the manufacturer's construction manual. Some smaller systems only need a small submersible water pump.