The first consideration to find a safe location for your water feature. For safety, you must first make sure that there are no underground utilities where you'll be digging and excavating for the installation. If you're uncertain, check with your local utility company before you dig. The location for our water garden is a lawn area at the rear of a local school. The space we will need is about 10 feet by 12 feet. Another important consideration is sun exposure. To grow healthy aquatic plants, you'll need adequate sun exposure. Most aquatic plants require four to six hours of sunlight per day to ensure healthy growth. Consider the slope of the land and the location of the pond in order to avoid rainwater runoff. If the pond is located in a low-lying area, lawn fertilizers and other chemicals could wash into the pond and harm the fish and plants.
Once you have a good general plan for your water garden, it's important to get your design on paper. Make a drawing on paper of a design that you like (Image 1). The design drawing is critical because it will allow you to make an accurate estimate of the amount of materials you'll need. The diagram also allows you to plan for all of the components of the design -- such as placement of the pump and skimmer, calculating the amount of plumbing you'll need to connect those components together. At this point, you should also plan for the amount of plant material that you may need for landscaping behind or around the pond (Image 2). Be sure to place the waterfall tank and the skimmer on opposite ends of the pond. This arrangement will ensure good water circulation and flow throughout the body of the pond. The waterfall not only serves to add visual interest and a pleasant sound, it also provides a functional role in filtration and oxygenation of the water.
A common mistake made by beginners when building a pond is the failure to consider the large amount of soil that will be removed during the excavation. Finding a use for a sizeable amount of excavated dirt -- or finding a method for disposing of it -- is an important consideration. For our project, we incorporated this factor into our overall design, opting to use the dirt to build up a berm at the rear the pond (between the pond and the exterior wall of the building) for landscaping. The berm will help in the placement of plants to create a natural look, and will also create a slope behind the waterfall to help create the illusion of a natural stream.
When you begin the design process, and after you've sketched out your basic design, use a garden hose laid out on the ground to experiment with the size and shape of your water garden. Our overall pond design calls for a shape that is roughly oval, with basic dimensions of 12 feet long and 10 feet wide. The depth is 18 inches at one end, sloping down to 24 inches at the other end. The skimmer is located at the shallow end, and the waterfall at the deeper end. The berm will provide a good backdrop for landscaping behind the pond and for creating the illusion that the cascade of the waterfall flows from a stream. As you decide on the size of your pond, be sure to take into consideration the rocks and aquatic plants you'll be adding later. Another common mistake among beginners is building a pond that seems big enough at first, but then appears too small once the rocks and plants are added.
Once you've arrived at the shape and dimensions that work best for you, use a spray marker to trace the boundary of your pond on the grass or dirt surface. Simply follow the outline of the garden hose you used to lay out the shape and dimensions of the pond. Spray-markers can be purchased from home centers or you can rent them. When you get ready to you purchase the liner material for your pond, be certain to take the depth of the pond into consideration. Taking our pond as an example, a 10'x12' pond needs a liner substantially larger than 10'x12' in order to also cover the sloping sides that drop to a depth of up to 24 inches.