1. What is Meyer's Evaporation Formula?

Meyer's formula is an empirical equation used to estimate evaporation loss from water surfaces. It considers factors such as vapor pressure difference and wind velocity to provide a monthly evaporation estimate.

2. How Does the Calculator Work?

The calculator uses Meyer's formula:

Where:

• \( E_m \) — Evaporation loss per month (Meter)
• \( C \) — Meyer's constant (1.1 for deep water, 1.5 for shallow water)
• \( \delta V \) — Change in vapour pressure (Pascal)
• \( u \) — Mean wind velocity (cm/s)

Explanation: The formula accounts for the combined effects of vapor pressure deficit and wind speed on evaporation rates from water surfaces.

3. Importance of Evaporation Calculation

Details: Accurate evaporation estimation is crucial for water resource management, irrigation planning, reservoir operation, and hydrological studies.

4. Using the Calculator

Tips: Enter Meyer's constant (typically 1.1 or 1.5), change in vapor pressure in Pascal, and mean wind velocity in cm/s. All values must be valid positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What are typical values for Meyer's constant?
A: Meyer's constant is typically 1.1 for deep water bodies and 1.5 for shallow water surfaces.

Q2: How is change in vapor pressure measured?
A: Change in vapor pressure is calculated as the difference between saturation vapor pressure and actual vapor pressure at the given temperature.

Q3: What is the significance of wind velocity in evaporation?
A: Wind velocity helps remove saturated air from the water surface, allowing more water molecules to evaporate, thus increasing evaporation rates.

Q4: Are there limitations to Meyer's formula?
A: The formula is empirical and may not be accurate for all conditions. It works best for average conditions and may require local calibration.

Q5: Can this formula be used for daily evaporation estimates?
A: While primarily designed for monthly estimates, it can be adapted for shorter periods with appropriate adjustments.