Koi Pond Design : Form And Function

KOI POND DESIGN --What is a koi pond, exactly? Definitions vary, but generally any ornamental body of water that is intended to provide the proper habitat to support koi falls into that classification. And although koi ponds lend serenity and peace to outdoor landscapes, many factors need to be considered to create these oases. Location, drainage issues, water depth, the presence of water features and filtration all need to work cohesively to achieve the perfect balance of aesthetics and functionality.

CHOOSING THE RIGHT LOCATION
Siting the location of a pond is initially determined by the anticipated  use of the space. Flow and sightlines are also key factors in determining the most suitable location. If, for example, the water feature is located in a far corner of the yard, then the space will feel separated from the home and landscape. Most people select the lowest point in the yard to locate their pond. It is, after all, where rain water tends to collect. Aesthetically this can prove to be the ideal location since in nature, water is found at the lowest point with its surroundings sloping
down to meet it. In residential situations, however, other factors need to be considered. Pollutants such as fertilizer collect in low-lying areas, which can affect water quality and potentially fish health. These areascan be used, however, as long as drainage and grading
considerations are taken into account during the design phase. (On very large-scale projects this becomes less of an issue, as sizeable volumes of water are less prone to fluctuations from pollutants.)

RESOLVING DRAINAGE ISSUES
When a low-lying area is determined to be the most suitable location for a pond, it is critical to consider drainage beyond its surrounding area. Ground water naturally tends to increase in lower-lying areas and can also collect under the lining material of the main basin, which can compromise the pond’s integrity. When enough hydrostatic p ressure is created below the mainbasin, it will heave upward. In rubber liner applications there appears to be a large “air bubble” below the liner; this bubble is actually filled with water. Using stone to hold the liner in place is not an effective solution, since the hydrostatic pressure, if great enough, will simply

RESOLVING DRAINAGE ISSUES
When a low-lying area is determined to be the most suitable location for a pond, it is critical to consider drainage beyond its surrounding area. Ground water naturally tends to increase in lower-lying areas and can also collect under the lining material of the main basin, which can compromise the pond’s integrity. When enough hydrostatic pressure is created below the main basin, it will heave upward. In rubber liner applications there appears to be a large “air bubble” below the liner; this bubble is actually filled with water. Using stone to hold the liner in place is not an effective solution, since the hydrostatic pressure, if great enough, will simply heave the boulders on top of the liner. Concrete basins are just as prone to heaving. The best remedy is to incorporate a relief system under the main basin using a series of perforated drainage pipes that are buried with washed gravel. Ground water then flows to a vault where it can be captured and used for irrigation or make up water to top off the pond.

DECIDING ON THE IDEAL DEPTH
The water depth of the main basin can vary. In the Midwest, a minimum depth of 3 feet is ideal, although for serious koi collectors, deeper is better. Deeper ponds not only increase the water volume, which then dilutes minor pollutants, but they also provide more vertical swim space for koi, promoting growth. In larger systems, treatments and quarantine typically need to occur in a separate system for both cost and effectiveness. The excavation design for the main pond should reflect appropriate depths. In both formal and natural koi pond designs this means factoring in rock and plant shelves, considering the slope of the vertical walls and the pitch of the floor, and siting ground water relief, bottom drain suction lines, pump returns and aeration supply lines.