The Evaporation Loss Calculator is designed to estimate how much liquid—typically water, fuel, or chemicals—is lost due to evaporation from open surfaces or storage tanks. This calculator is widely used in hydrology, agriculture, industrial operations, and environmental engineering to manage resources, optimize systems, and comply with environmental regulations.
By using specific variables such as surface area, evaporation rate, and correction factors for environmental conditions, the calculator helps users predict and mitigate water loss in ponds, reservoirs, or storage tanks. It also adapts to industrial applications using the API (American Petroleum Institute) standard method for volatile liquid storage.
Formula of Evaporation Loss Calculator
For Open Water or Surface-Based Evaporation:
Evaporation Loss = (A × E × K) / 1000
Where:
- Evaporation Loss = volume lost in cubic meters per time unit (e.g., day or month)
- A = surface area of the water body (in m²)
- E = evaporation rate (in mm/day or mm/month)
- K = correction factor (typically 0.6 to 1.0) based on wind, exposure, and temperature
- Division by 1000 converts millimeters to meters
If correction is not applied:
Evaporation Loss = (A × E) / 1000
For Storage Tanks Using API Standard:
Evaporation Loss = (12 × V × P × MW) / (R × T × H)
Where:
- V = vapor space volume (m³)
- P = vapor pressure of the liquid (kPa)
- MW = molecular weight of the vapor (kg/kmol)
- R = gas constant (8.314 kPa·m³/kmol·K)
- T = absolute temperature in kelvin (K)
- H = tank height (m)
This formula estimates vapor emissions due to breathing and standing losses in closed tanks.
Helpful Reference Table
Below is a reference table for estimated evaporation losses under different conditions, assuming no correction factor (K = 1.0):
| Surface Area (m²) | Evaporation Rate (mm/day) | Daily Loss (m³/day) |
|---|---|---|
| 100 | 5 | 0.50 |
| 500 | 3 | 1.50 |
| 1000 | 6 | 6.00 |
| 2500 | 2 | 5.00 |
| 5000 | 7 | 35.00 |
This table helps users quickly estimate potential losses for irrigation ponds, industrial tanks, or water reservoirs.
Example of Evaporation Loss Calculator
Let’s calculate daily evaporation loss from a water reservoir with the following data:
- Surface Area (A): 1200 m²
- Evaporation Rate (E): 4 mm/day
- Correction Factor (K): 0.9
Step 1: Plug into the formula
Evaporation Loss = (1200 × 4 × 0.9) / 1000
Evaporation Loss = 4320 / 1000 = 4.32 m³/day
Result: The reservoir loses approximately 4.32 cubic meters of water per day due to evaporation.
Most Common FAQs
The correction factor (K) accounts for environmental variations like wind speed, sunlight exposure, and humidity. These factors influence the actual evaporation rate, making the estimate more accurate for real-world conditions.
Yes. For chemical or fuel storage tanks, the API method should be used. It considers vapor pressure, temperature, and molecular properties to estimate evaporative losses more accurately.
Use mm/day or mm/month for surface-based calculations. Ensure that your surface area is in square meters to keep the output in cubic meters. For industrial tank applications, vapor pressure should be in kPa, and temperature in kelvin (K).