Springs and Ponds - a double edged sword
Are springs a good sign when selecting a pond site?
The short answer is yes...... and no. There are many factors to consider when answering that question.
Springs are simply a connection between groundwater and surface water. Many times, the key is the elevation of the spring. If the spring is above the planned water surface elevation for the pond, it is almost always a good thing.
If the spring is below the planned water surface elevation for the pond there are far more questions to answer. Because the spring connects groundwater and surface water, it can function as a water source BUT can also serve as a drain if there is not enough pressure in the groundwater to overcome the weight of the water in the pond. Further complicating the question is the fact that groundwater pressure and flow will vary from season to season and with local rainfall.
In some cases, it is possible to locate the pond reservoir below the spring. If there is high quality clay or the builder supplements the existing soil with bentonite or other bottom sealing amendments a successful pond may be constructed. Care should be taken to evaluate the soils and complete a water budget for the pond before starting construction.
If it is not possible to avoid springs lower than the planned pond water surface there are measures that can be taken to ensure success. Most often a geomembrane liner system is used to isolate the pond water from the springs preventing the springs from draining the pond when groundwater pressure is low. The spring water can still be captured and used in the pond by installing an underliner drain which can be connected to a pump if necessary to draw the spring water from under the liner.
Careful planning is critical when springs are present at or near the planned pond location. A pre-construction pond site evaluation is highly recommended.