Evaporation Rate Calculator
Calculate water evaporation rates for pools, ponds, and water bodies
Evaporation Rate Calculation
Surface Area
Surface area of water body exposed to air
Air Speed (Wind)
Wind speed above water surface (check weather report)
Air Temperature
Air temperature at water surface
Relative Humidity
Percentage of maximum humidity (0-100%)
Results
Calculation Breakdown
Humidity Analysis
Example Calculation
Garden Pond Evaporation
Given:
• Surface area: 20 ft² (1.86 m²)
• Air speed: 5 mph (2.24 m/s)
• Temperature: 68°F (20°C)
• Relative humidity: 70%
Solution
Xs = 3.733×10⁻³ + 3.2×10⁻⁴×20 + 3×10⁻⁶×20² + 4×10⁻⁷×20³
Xs = 0.01501 kg/kg
X = 0.01501 × 0.70 = 0.01051 kg/kg
gh = (25 + 19×2.24) × 1.86 × (0.01501 - 0.01051)
gh = 67.56 × 1.86 × 0.0045 = 0.565 kg/hr
Result: 1.25 lb/hr or 0.15 gal/hr
Factors Affecting Evaporation
Temperature
Higher temperature = faster evaporation
Humidity
Lower humidity = more evaporation
Wind Speed
More wind = faster evaporation
Surface Area
Larger area = more total evaporation
Typical Rates
Understanding Water Evaporation
What is Evaporation?
Evaporation is the process where water molecules at the surface of a liquid gain enough energy to escape into the air as water vapor. This process occurs continuously but at different rates depending on environmental conditions.
Evaporation Formula
The evaporation rate formula accounts for wind speed, surface area, and humidity difference:
gh = (25 + 19 × v) × A × (Xs - X)
Where wind enhances evaporation by removing water vapor from the surface
Humidity Ratios
Humidity ratios measure the amount of water vapor in air compared to dry air. The difference between maximum and current ratios drives evaporation.
Practical Applications
Pool Management:
Calculate water loss for refilling schedules
Agriculture:
Estimate irrigation water requirements
Weather Studies:
Understand local water cycle patterns
Environmental Impact
Understanding evaporation rates is crucial for water conservation, climate studies, and efficient management of water resources. Seasonal variations in temperature, humidity, and wind patterns significantly affect annual water loss from open bodies.
Note: The empirical formula is most accurate for temperatures between 0-30°C (32-86°F). For extreme temperatures, additional corrections may be needed.