Building a Pond : Digging the Hole



 

Building Garden Ponds and Waterfalls

Once the site and design for the garden pond and waterfall has been selected it is time to start building the pond by digging the hole and building up elevated areas if necessary. This is either going takes physical labor on your part or the expense of paying someone else to do the work. There is no getting around this and it is important to note that learning about building a pond correctly saves work and expense down the road.
 
My first pond, I excavated and laid the liner and plumbing myself. My second one I paid someone to dig the hole and did the rest myself. For the third pond I hired a landscaper to do the entire job. This was more expensive but it saved me an enormous amount of work since this pond is 40ft by 25ft and over 5 ft deep in the center. In all cases, I was very much involved in the design and fully understood how the pumps, filters and skimmer worked. If you enjoy working outdoors by all means do as much of the work yourself as is practical. The size of the pond, the difficulty of the terrain and what you can afford to pay drives this decision.

 

The First Step in Building a Pond – Excavation or “Digging the Hole”

1) The first step is to roughly outline the shape of the pond. You can do this with a hose, rope, chalk, wooden pegs, whatever suits you.

2) If you plan on building a pond on a slope you will need to ensure that it is level across its width and along its length. If not the water will spillover at one end and the liner will be exposed at the other. String/boards and a level can be used to measure and ensure equal elevation at all borders of the pond and a berm or retaining wall can be used to build up the lower areas. It is paramount that the berm/wall be strong enough to retain the pressure that will be exerted by the water in the pond. For steeper slopes, one large waterfall or a series of cascading ponds can address this issue with a very nice effect. (illustration below)

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Cascading Waterfalls

3) The depth of the pond can vary over its base but, a koi pond, particularly in a cold weather area, should be at least 4 – 5 feet at its deepest point. There should also be shallower areas or shelves (1 to 2 feet deep) for plants.

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Excavating a Koi Pond with Shelves for Plants

 

4) Begin building the pond by digging in the center and work outward placing the soil on the side that needs to be raised up for either the leveling described in step 2 or to incorporate a features such as a waterfall or stream. Once the hole is dug tap down the soil and remove any rocks, tree roots or other sharp objects or protrusions that could damage the liner.

5) Garden pond waterfalls or streams must be located at a higher elevation so they cascade back into the lower pond. The height above and distance from the pond is determined by the natural terrain, the amount of pipe you are willing to install and the capacity of the pump you use. Most pumps will come with a standard rating of gallons per hour and a table that adjusts that capacity for different heights and distances. Ideally, in a koi pond, you will want a pump with the capacity to turn over the full volume of the pond once an hour and no less than once every 2 hours.

 

Volume Calculator for Building a Pond

1) The volume of the pond in gallons can be calculated as: the surface area X average depth X 7.5. The surface area can be estimated as length X width for ponds that approximate a rectangle or by 3.14 X the diameter for ponds that are closer to a circle. Another approach for determining the volume is when filling the pond, measure the flow rate out of the hose and then time how long it takes to fill the pond. So if the flow rate is 5 gallons per minute and it takes 4 hours (240 minutes) to fill, the volume is 1,200 gallons. In any case the volume estimate does not have to exact and an approximation is good enough. A simple pond volume calculator follows. Enter the length, width and average depth in feet for a pond that approximates a rectangle and the diameter and average depth for a pond that is closer to a circle and the calculator will determine the volume of the pond in gallons:

 
 

This cutaway view illustrates one example of an excavated garden pond and waterfall.

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Cutaway of Excavated Pond with Plant Shelf and Waterfall

 

 

Next select and install the Pond Liner

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