Question

The instrument which is used to measure evapotranspiration in the field condition is:

• A. Evaporimeter
• B. Current meter
• C. Lysimeter
• D. Pyrometer

Hint:

Don't confuse Evaporation with Evapotranspiration. An Evaporimeter (like a Class A pan) measures potential evaporation from a water surface, while a Lysimeter measures actual evapotranspiration from a soil and plant system.

Answer 1

The Correct Option is C

Step 1: Define Evapotranspiration (ET). Evapotranspiration is the sum of water evaporation from the soil surface and transpiration from plants. It is a key component of the hydrologic cycle.
Step 2: Analyze the function of each instrument.
- Evaporimeter (or Pan Evaporimeter): Measures the rate of evaporation from an open water surface. It provides an estimate but does not directly measure ET from a vegetated surface.
- Current meter: Measures the velocity of flowing water in a river or channel.
- Lysimeter: A measuring device used to measure the actual evapotranspiration released by plants. It consists of a block of soil with vegetation, placed in a container, allowing for the measurement of water input (precipitation, irrigation) and output (drainage), with the difference representing ET.
- Pyrometer: Measures temperature, typically high temperatures, from a distance by detecting thermal radiation.
Step 3: Conclude the correct instrument. Based on the functions, the Lysimeter is the specific instrument designed to directly measure evapotranspiration under field conditions.