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Building Waterfalls for Residential Properties

Description/Purpose:

The addition of a waterfall to an existing water garden can provide excitement and relaxation through the sight and sound of moving water. In addition, a waterfall may also serve as a filtering system or a means to oxygenate the water. Although a waterfall may be constructed from concrete or a preformed liner, the use of a flexible liner covered with natural stone will work best for the cold winter climate of the upper Midwest.

Liner Length


Liner Width



Amount, Specifications & Supplies:

Butyl rubber and EPDM (ethylene propylene diene monmer--a synthetic rubber) are the two best flexible liners for water garden construction. Each of these materials is UV stable and should last 20 years or more. EPDM and butyl rubber are generally available in 45 mil and 60- or 30-mil thicknesses, respectively. While the 60 mil thickness may provide better resistance to punctures, the thicker material is more difficult to work with and is not necessary if the excavation has been prepared properly. PVC liners may also be used for waterfall construction, however this material is not as durable and should not be expected to last as long as butyl rubber or EPDM liners. To determine the length of the liner needed, include the total length of the water course plus two times the maximum depth of the channel, plus two times the depth of each pool within the water course and an additional one foot which will overlap the existing pond liner. The width of liner is calculated by adding the width of the channel at its widest point and twice the depth of the channel at its deepest plus an additional one foot (six inches of overlap on each side).

Channel Excavation


Anatomy of a Waterfall Water Course



Underlays are recommended beneath liners unless the excavation is free of sharp rocks and any other potential puncture producing objects. Newspaper (one inch thick), cardboard, old carpet padding and fiberglass insulation have all been successfully used as underlayment. In addition, special fabric underlays or geothermal textiles are usually available where pond liners are sold. While the special fabrics may be more expensive than the other material, they are usually easier to install.

Stone of varying sizes will cover the liner when the watercourse is complete. Small river rock from 3/8" to 3" will be used to cover most of the horizontal surfaces between the falls; one ton will cover approximately 100 square feet to a depth of 2 inches. Larger field stone will be used for the sides of the channel and the spill rocks for the falls. There are approximately 40 6"-12" field stones per ton. The falls may also be constructed of flagstone, slate or other flat rock. This material is generally much more expensive and the coverage is determined by the thickness of the stone. In most cases the supplier from whom the stone is purchased will help determine the quantity of material needed.

A pump will be needed to recirculate water from the main pond through the water course. Pump size is usually based on the gallons of output per hour at one foot of height (lift). To establish the pump size required to achieve the desired effect use the following procedure: using a garden hose, adjust the flow rate until desired level of water action over the falls is attained. Fill a five gallon bucket at the determined rate, timing the number of seconds it takes to fill the bucket. Divide 3600 (number of seconds in an hour) by the number of seconds it took to fill the bucket, multiply that number by 5 (the number of gallons in the bucket) to determine gallons per hour required. It is usually recommended that the pump size (flow rate per hour) not exceed the volume of the main pond. If the lift of the falls is greater than one foot you will need to use the following chart to approximate the pump size needed. Submersible pumps are suitable for most residential water features, However, surface pumps will generally provide the highest outputs. Consult with a professional when selecting pumps where high output is required.

GPH @ 1', 3', 5' & 10' Lifts
1' 3' 5' 10'
120 70
170 140 100
205 168 120
300 255 205 70
325 300 270 130
500 435 337 210
600 580 517 414
710 690 670 580
810 790 745 613
1200 1170 1100 1000
Nash, p. 139

Systems combining surface skimming, filtration and waterfalls are available. If these systems are to be used follow the manufacturers' instructions for installation.

Tubing will be needed to move the water from the main pond to the water course. Check the dimension of the pump outlet before purchasing the pipe. In general, a ½" pipe will deliver up to 120 GPH, ¾" pipe up to 350 GPH, 1" pipe up to 1000 GPH and a 1¼" pipe up to 1500 GPH.

Electricity will be required for the pump. Outlets should be at least four feet from the pond and should be enclosed in a waterproof casing. Surface pumps require a dedicated circuit. If underwater or above ground lighting is going to be used it should also be wired at this time.

Insulation foam is used in place of mortar or concrete to fill gaps between stones or between stones and the liner. The foam need only be used in those instances when water needs to be diverted in a specific direction.

Tools and Equipment:

  • Gravel shovel for excavation of the water course
  • Flat-backed shovel for finishing the sides of the channel and the face of the falls
  • Rake to level the horizontal surfaces
  • Carpenter's level for checking the sides of the header pool and the spill rocks
  • Hand tamper to tamp freshly excavated soil which is to become part of the water course
  • Stone chisel to shape rocks and carve grooves
  • Insulation gun for applying poly foam
  • Goggles to protect eyes from flying stone chips
  • Wheel barrow to haul rock and soil
  • Garden hose for water
  • 1 lb. hammer to chisel rocks

Site Considerations:

A grade change of some extent is required for a waterfall feature. Often this grade change is nothing more than the soil from the pond excavation. Freshly dug soil will need to be tamped in 2 to 3 inch layers to provide adequate support for the water course. To create a natural looking waterfall, the falls should start eight to ten feet from the pond. This will allow for the construction of a header pool and a primary falls that does not flow directly to the main pond, thereby minimizing the disturbance to plants which dislike moving water.

Step-By-Step Process:

1. Drain water from the existing pond. Remove any rocks in the immediate vicinity of the proposed waterfall.

2. Lay out the proposed water course with wooden stakes and string. Make certain to carefully mark the header pool and each area where the grade changes.

3. Excavate the channel for the water course. Begin at the existing pond and work back toward the header pool. A gravel shovel can be used for moving most of the soil, while the straight back spade will be used for shaping the side and base of the trench. A garden rake will be used to level the base and to remove stones and other debris from the base of the trench. Use the level to check the side of the header pool and lip of each waterfall. Except for the area of the header pool the entire area should slope towards the main pond. The header pool and any other pools within the water course will actually slope towards the back of the pool.

Waterfall Channel



4. Cover the excavation with the chosen underlay material. The underlayment does not need to extend further than the top of the pool or sides of the channel.

5. Lay the flexible liner over the water course excavation. Unrolling the liner and lying it flat in the sun for about one half hour prior to setting in the trench will allow the liner to better conform to the shape of the water course. A minimum of six inches of the liner should overlap the existing pond liner. Pleat any large creases as necessary.

6. With the liner in place run water through the water course to check levels and possible leakage. Once satisfied with the performance of the liner remove the water from the liner and proceed to the next step.

7. Lay stone in the water course beginning at the lower end and working towards the top. The first stone laid is the foundation stone, this stone will need to be flat on the top and bottom since it sits on the shelf of the pond and is the base for the spill stone of the falls flowing directly into the pond. Keep the following in mind as the remainder of the stone is laid:

The stone on either side of the spill stone should be higher than the spill stone to force the water to flow over the spill stone.

Spill stones should slope gently towards the main pond.

Use poly foam to adhere the spill stone to the liner; a hand full of sand thrown on the foam immediately after application will camouflage the foam. Poly foam should be used anywhere water must run over the stone rather than under or around them.

After the vertical surfaces of the water course are covered with large stones, the horizontal surfaces may be covered with a layer of river rock and small cobbles.

8. Using the garden hose fill the header pool and allow the water to run the entire course. Make final alterations as necessary. Install lighting if desired.

9. With an adequate length of delivery pipe attached to the submersible pump, lower it into the main pond. Run the delivery pipe along the water course and up to the header pool. Plug in the pump and check to make sure the pump is large enough to give the desired effect. After testing the pump, bury the delivery pipe several inches below the surface. The delivery pipe should enter above the level of the header pool; careful placement of rocks should conceal the pipe.

References:

Nash, Helen. The Complete Pond Builder. Sterling Publishing, New York (1996).

Robinson, Peter. The American Horticultural Society Complete Guide to Water Gardening. DK Publishing, New York (1997).

Folsom, Kieth M. "Building a Waterfall." Carolina Gardener. Vol. 9 no. 6, August, 1997, pp. 20-24.

Aquascapes Designs Inc. Advanced Construction Techniques. Aquascape Design, West Chicago, IL.

This implementation report was developed by Michael Buechner, Environmental Horticulture Student.

 
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