Pond Evaporation Rate Calculator
Estimate the daily water loss from your pond or water feature based on environmental conditions.
Estimated Water Loss
Daily Loss Depth:
0.00 inches
Daily Volume Loss:
0.00 gallons
Weekly Volume Loss:
0.00 gallons
Monthly Volume Loss:
0.00 gallons
Understanding Pond Evaporation
Pond owners often worry when they notice water levels dropping, immediately fearing a leak. However, evaporation is a natural and significant cause of water loss. On a hot, dry, and windy day, a typical pond can lose between 1/4 and 1/2 inch of water depth.
This calculator uses a simplified version of Dalton's Law of partial pressures and empirical mass-transfer formulas to estimate how much water your pond is losing to the atmosphere.
Key Factors Influencing Evaporation
- Temperature: Higher air and water temperatures provide more energy for water molecules to escape into the air as vapor.
- Relative Humidity: If the air is already saturated with moisture (high humidity), it cannot easily accept more water vapor, slowing evaporation. Dry air accelerates it.
- Wind Speed: Wind moves the saturated air directly above the water surface away, replacing it with drier air and significantly increasing the evaporation rate.
- Surface Area: The larger the surface area of your pond, the more "interface" there is for evaporation to occur.
Example Calculation
Imagine a 1,000 sq. ft. pond during a summer heatwave:
- Temperature: 90°F
- Humidity: 30%
- Wind Speed: 10 mph
Under these conditions, the pond might lose approximately 0.35 inches of depth per day. Over 1,000 square feet, that equates to roughly 218 gallons of water lost every single day.
Is it a Leak or Evaporation? (The Bucket Test)
If you suspect a leak, perform the "Bucket Test":
- Fill a bucket with pond water and set it on a flat surface next to the pond (or on a pond step so it is partially submerged to maintain the same temperature).
- Mark the water level inside the bucket and the water level of the pond.
- Wait 24 hours.
- Compare the drop in both. If the pond level dropped significantly more than the bucket level, you likely have a leak. If they dropped the same amount, it is just evaporation.
How to Reduce Pond Evaporation
While you cannot stop evaporation entirely, you can minimize it by:
- Adding Aquatic Plants: Floating plants like lilies cover the surface, shading the water and reducing the area exposed to air.
- Windbreaks: Planting shrubs or installing fences around the pond can reduce the wind speed across the surface.
- Turning off Waterfalls at Night: Waterfalls and fountains increase surface area exposure; turning them off when not being enjoyed can save water.