Evaporation Loss Per Month Calculator

Meyer's Formula:

\[ E_m = C \times (V - v) \times \left(1 + \frac{u}{16}\right) \]

Meyer's Constant:

Maximum Vapour Pressure:

cm Hg

Actual Vapour Pressure:

cm Hg

Mean Wind Velocity:

m/s

Evaporation Loss Per Month:

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is Meyer's Evaporation Formula?

Meyer's formula is an empirical equation used to estimate evaporation loss from water surfaces. It accounts for vapor pressure differences and wind velocity to provide monthly evaporation estimates.

2. How Does the Calculator Work?

The calculator uses Meyer's formula:

\[ E_m = C \times (V - v) \times \left(1 + \frac{u}{16}\right) \]

Where:

\( E_m \) — Evaporation loss per month (m)
\( C \) — Meyer's constant (1.1 for deep water, 1.5 for shallow water)
\( V \) — Maximum vapour pressure (cm Hg)
\( v \) — Actual vapour pressure (cm Hg)
\( u \) — Mean wind velocity (m/s)

Explanation: The formula calculates evaporation based on the vapor pressure deficit and wind speed enhancement factor.

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 vapor pressures in cm Hg, wind velocity in m/s, and select appropriate Meyer's constant. All values must be valid (vapor pressures > 0, wind velocity ≥ 0).

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between deep and shallow water constants?
A: Deep water (1.1) applies to large, deep water bodies with stable temperatures, while shallow water (1.5) applies to smaller, shallower water bodies with more variable temperatures.

Q2: How accurate is Meyer's formula?
A: Meyer's formula provides reasonable estimates for monthly evaporation but may have limitations in extreme climatic conditions or for very short time periods.

Q3: What are typical evaporation rates?
A: Evaporation rates vary significantly by climate, ranging from 1-3 m/year in arid regions to 0.5-1.5 m/year in temperate regions.

Q4: How does wind affect evaporation?
A: Wind increases evaporation by removing saturated air from the water surface and replacing it with drier air, enhancing the evaporation process.

Q5: When should Meyer's formula not be used?
A: The formula may be less accurate for very small water bodies, in extreme temperature conditions, or when precise daily evaporation estimates are required.