How Much Evaporation is Normal?
We are frequently asked how much evaporation is normal in a water garden as concerned pond keepers try to determine if there is a leak in the pond. Unfortunately there are too many variables to have a formula for calculating evaporation. To add to the uncertainty evaporation is not the only normal means of water loss in the pond.
For a pond to lose ½” – 3/4” of water per day under certain extreme conditions is not terribly uncommon and probably no cause for alarm. The amount of water evaporating will depend on several factors including; cloud-cover, shade over the pond, humidity, wind, and the specifics of the waterfall or fountain. The longer a stream the more water is exposed to the air greatly increasing evaporation.
Water features can also lose water to splash out of waterfalls or fountains. This could be due to windy conditions or simply design flaws in the feature itself. Plants also will absorb some water. Another possibility short of a leak is losing water to wicking. This can occur if a plant, roots, mulch, pond underlayment or other material hangs into the pond and allows water to slowly wick out.
If you are convinced that your water feature has a leak the next step is to locate the pond leak.