1. What is Actual Evapotranspiration?

Actual Evapotranspiration is the quantity of water that is actually removed from a surface due to the processes of evaporation and transpiration. It represents the actual water loss from the land surface to the atmosphere through these combined processes.

2. How Does the Calculator Work?

The calculator uses the water balance equation:

Where:

• \( E_{act} \) — Actual Evapotranspiration (m³/s)
• \( P \) — Precipitation (m)
• \( \Delta S \) — Change in Moisture Storage (m)
• \( S_r \) — Surface Runoff (m³/s)
• \( G_o \) — Subsurface Outflow (m³/s)

Explanation: This equation represents the water balance approach where actual evapotranspiration is calculated as the residual term when all other water balance components are known.

3. Importance of Actual Evapotranspiration Calculation

Details: Accurate calculation of actual evapotranspiration is crucial for water resource management, agricultural planning, irrigation scheduling, climate studies, and understanding the hydrological cycle. It helps in assessing water availability and demand in various ecosystems.

4. Using the Calculator

Tips: Enter precipitation in meters, change in moisture storage in meters, surface runoff in m³/s, and subsurface outflow in m³/s. All values must be non-negative and valid measurements.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between potential and actual evapotranspiration?
A: Potential evapotranspiration is the maximum amount of water that could evaporate and transpire under ideal conditions, while actual evapotranspiration is the real amount that occurs given current environmental constraints.

Q2: Why is actual evapotranspiration important in agriculture?
A: It helps farmers determine irrigation requirements, optimize water use efficiency, and schedule watering to match crop water needs while conserving water resources.

Q3: What factors affect actual evapotranspiration rates?
A: Solar radiation, temperature, humidity, wind speed, soil moisture availability, vegetation type and density, and land use practices all influence actual evapotranspiration rates.

Q4: How is this method different from other evapotranspiration measurement techniques?
A: The water balance method provides an integrated measure over a catchment area, while other methods like lysimeters or eddy covariance provide more localized measurements.

Q5: What are the limitations of the water balance method?
A: This method assumes accurate measurement of all other water balance components and may accumulate errors from each measured parameter. It works best for closed basins with well-defined boundaries.