How is potiential evaporation measured?

To measure potential evaporation, various methods can be used depending on the level of accuracy required. One commonly used method is the Class A Evaporation Pan. Here's an explanation of how potential evaporation can be measured using this method:

Step 1: Setup -
1. Select a suitable location for the evaporation pan, preferably in an open area away from obstructions such as trees or buildings.
2. Dig a hole in the ground large enough to accommodate the pan. Ensure that the rim of the pan is level with the surrounding ground.
3. Place the evaporation pan in the hole, making sure it is stable and fully supported.
4. Fill the pan with distilled or rainwater, leaving a small gap at the top to allow for any overflow.

Step 2: Monitoring -
1. Measure the initial water level in the evaporation pan. This is your starting point.
2. Keep a record of the water level in the pan at regular intervals, preferably once a day. This can be done using a measuring stick or a calibrated rule.
3. Note down other essential parameters such as temperature, humidity, wind speed, and solar radiation, as these factors influence evaporation rates.

Step 3: Calculation -
1. Calculate the daily evaporation by subtracting the final day's water level from the initial day's water level.
Daily Evaporation = Initial Water Level - Final Water Level
2. Convert the daily evaporation to a monthly or yearly average by summing up the daily values and dividing by the number of days.
Monthly or Yearly Average Evaporation = Sum of Daily Evaporation / Number of Days
3. If desired, consider the meteorological factors collected in Step 2 and analyze their influence on the evaporation rate.

It's important to note that potential evaporation measurements serve as an estimate of the evaporation that would occur under ideal conditions. Various other methods, such as lysimeters, weather station records, and modeling techniques, can also be used to measure potential evaporation, depending on the level of accuracy required and the available resources.