Rate of Evaporation (\( E \)):

\[ E = (11 + 0.68 W) (C_s - C_d) \]

Where:

• \( E \) is the rate of evaporation, in millimeters per day (mm/day).
• \( W \) is the average wind velocity at 0.15 meters, in kilometers per hour (kph).
• \( C_s \) is the saturated vapor pressure at the temperature of the water surface, in millimeters of mercury (mm Hg).
• \( C_d \) is the actual vapor pressure of the air, calculated as \( C_s \) multiplied by the relative humidity, in millimeters of mercury (mm Hg).