Adding natural water features such as small ponds is becoming more popular. On both the homeowner and farm level, as well as urban beautification it allows for introduction of a natural environment that encourages wildlife and may give recreation opportunities as well. Contrary to common belief it is not quite as simple as digging a hole and waiting for it to fill with water. A qualified engineer can help determine the requirements for a specific location and purpose to build a small pond.
The most important consideration is the type of ground you want to build it on. Clay, sand, soil, and rock all have very different properties in regards to ability to hold water. In a very sandy area no amount of water will ever keep a pond from simply seeping away. Excavating a hole in soil and filling it with water will result in a mud pit as opposed to a pond. This is why a site survey must be done to determine what will be needed to result in a stable clean pond.
In addition to what the top of the ground is, what is underground will impact the pond design. One key piece of information is how far down until the bedrock. This is impost as it determines depth of pond usually. Taking it down to the bedrock when practical ensures a stable bottom for the pond that will usually hold water with little additional material or fill. Breaking through the bedrock, in addition to being very labour intensive, may make it impossible for the pond to hold water as opposed to draining off in the water table.
The level of the water table can be used to benefit as well. Sometimes a small hole or series of holes can be drilled into the water table to ensure a steady amount of fresh natural ground water in the pond. This is particularly useful if planned for wildlife use or to introduce fish to the pond.
Before You Dig
Prior to getting used excavators onsite and digging out a pond get a proper site survey. Then you will have the proper natural materials on hand to line the bottom of the pond if needed while the excavators are on site to spread it. It will be a far simpler job to do correctly the first time than to try to drain off and fix later. It can also prevent mishaps like the hole filling rapidly with groundwater before excavation is complete.