Aquaculture Engineering

Maintenance of ponds - Evaporation

Unit 5- Construction of Fish ponds

Maintenance of ponds

Evaporation

Definition
Evaporation is the process by which water is converted into gaseous stage and is returned to the atmosphere as vapour. The water is continuously evaporating from the water surface of natural and artificial sources like river, streams, ponds, reservoir etc.,water evaporates from the surface of the soil also. As such a part of the precipitation reaching the earth’s surface is lost through evaporation.

Evaporation depends upon several factors such as temperature, humidity, wind velocity, atmospheric pressure, salinity of water and surface area. The rate of evaporation increases with the increase of temperature as well as wind velocity and vice versa. The rate of evaporation decreases with increase of humidity and increases of dissolved salts in water. Evaporation increases when the surface area increases. Rate of evaporation is increases with decreasing of atmospheric pressure.
To find out the rate of evaporation commonly used methods are

• Empherical formula.
• Direct measurement with the help of evaporation pan.