Whether you're building a pond from scratch or working on pond maintenance or repairs, understanding water supply is basic to getting the job done. What follows is a brief review of pond water sources for reference in your pond projects.
Your pond may use one or more of these water types to fill and maintain good water quality.
Ground water is the most basic pond water. This is the water you find when you dig test holes to explore for a water source. Sometimes called static water level, or water table, ground water may be level with the surrounding grade, or just a few inches deep at the bottom of a test pit, or somewhere in between. The ground water level often varies during the seasons, from high in spring to low in dry summer, and then back up again with fall and winter rains and runoff. Most natural earth ponds depend on some degree of ground water to be successful, which may be supplemented by another water source to complete the fill and ideally get the pond overflowing to prevent stagnation.
Supplementing ground water are several other types of potential sources.
Watershed runoff. Any land at a higher elevation than the designed pond water level that can be directed into the pond is a potential water source. Runoff potential will depend on acreage of the watershed, slope, and type of vegetation on the terrain. And of course the amount of rain or snow melt from the watershed. Runoff is often more significant in the east than the drier west.
Springs. Ponds may have springs in the basin which contribute to the general ground water. Pond swimmers may locate springs when they encounter colder water, or as dark spots or open water in winter ice. Springs may be visible bubbling out of the ground when ponds are dug. Spring activity may vary naturally during the year, and springs can be blocked up over time under sediment buildup.
Springs outside the pond can be a good source of water supply. Ideally springs will be above the pond so they can run by gravity to the pond. Some simply run from the surface downhill via a watercourse, hose or pipe, or are captured in a dug well and piped to the pond. If the spring is downhill from the pond it may be pumped to the pond.
Wells. Where pond water shortages are acute, a well may be used for supply. Perhaps there is an existing well with enough capacity to be used for the pond. Or a new well may be dug or drilled for supply. But well drilling is often a gamble, and not cheap, so it may be a last ditch effort to gain supply. Hiring a dowser to locate and predict well capacity may improve your chances.
Roof runoff capture systems are sometimes used for water supply. Ideally the structures will be above the pond so water can run by gravity. The water may be captured by a gutter system or a foundation drain.
Streams and rivers are a traditional water source for ponds. Again, if the source is higher in elevation than the pond all the better for gravity flow. Catching the water from a stream or river can be tricky because over time intakes are liable to be buried in sediment, and require periodic cleaning.
Sometimes structures such as perforated well tiles are installed in the water to protect the intake from sediment. Such structures may work best if installed alongside the stream, catching water seepage but avoiding sediment and flood damage.
Because earth ponds are inherently leaky, a combination of the above water sources may be needed to fill supply requirements.
Topics vary from month to month and provide great information when researching where you want to build a pond, or how to keep it clean. Other areas of interest are pond use for more than swimming, and how to keep fish happy in your pond.