Hydrology & Water Resources Engineering - Vol 2 | 20. Measurement of Evapotranspiration by Abraham | Learn Smarter
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20. Measurement of Evapotranspiration

20. Measurement of Evapotranspiration

Evapotranspiration encompasses the combined processes of evaporation and transpiration, playing a vital role in the hydrologic cycle and water resource management. Accurate measurement methods, both direct and indirect, include lysimeters, water balance, and remote sensing techniques, which provide insights into water balance, irrigation planning, and drought assessment. Various factors such as climate and plant characteristics influence evapotranspiration rates, which can be quantified using mathematical models and empirical methods.

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  1. 20
    Measurement Of Evapotranspiration

    Evapotranspiration is the process combining evaporation and transpiration,...

  2. 20.1
    Evapotranspiration – Basic Concepts

    Evapotranspiration combines evaporation and transpiration processes,...

  3. 20.2
    Factors Affecting Evapotranspiration

    Multiple climatic, soil, and plant-related factors influence the process of...

  4. 20.3
    Methods Of Measurement Of Evapotranspiration

    This section outlines both direct and indirect methods for measuring...

  5. 20.3.1
    Direct Methods

    Direct methods measure evapotranspiration through actual field observations,...

  6. 20.3.1.a
    Lysimeter Method

    The lysimeter method involves using a specialized tank to measure...

  7. 20.3.1.b
    Field Experimental Plots

    Field experimental plots utilize controlled water applications and observe...

  8. 20.3.2
    Indirect Methods

    Indirect methods utilize meteorological and empirical data to estimate...

  9. 20.3.2.a
    Water Balance Method

    The Water Balance Method estimates evapotranspiration (ET) using a...

  10. 20.3.2.b
    Energy Balance Method

    The Energy Balance Method estimates evapotranspiration (ET) based on the...

  11. 20.3.2.c
    Aerodynamic Method

    The Aerodynamic Method estimates evapotranspiration using wind speed and...

  12. 20.3.2.d
    Combination Method (Penman Equation)

    The Combination Method, illustrated by the Penman Equation, integrates both...

  13. 20.4
    Empirical Methods

    Empirical methods utilize well-established equations to estimate...

  14. 20.4.1
    Blaney-Criddle Method

    The Blaney-Criddle Method is an empirical formula used to estimate...

  15. 20.4.2
    Thornthwaite Method

    The Thornthwaite Method estimates potential evapotranspiration (PET) based...

  16. 20.4.3
    Hargreaves Method

    The Hargreaves Method is a simplified approach for estimating...

  17. 20.5
    Measurement Of Pan Evaporation

    Pan evaporation measurements are crucial for estimating reference...

  18. 20.6
    Remote Sensing And Et Estimation

    Remote sensing offers advanced tools to estimate evapotranspiration (ET)...

  19. 20.7
    Use Of Lysimeters In India

    Lysimeters in India are critical tools used in agriculture to measure...

  20. 20.8
    Crop Coefficients And Reference Et (Et₀)

    This section discusses the computation of reference evapotranspiration (ET₀)...

What we have learnt

  • Evapotranspiration is a key component of the hydrologic cycle.
  • Measurement of evapotranspiration is essential for effective water resource management.
  • Both direct and indirect methods can be employed to estimate evapotranspiration accurately.

Key Concepts

-- Evapotranspiration
The total water loss from both evaporation and transpiration processes.
-- Potential Evapotranspiration (PET)
The amount of evapotranspiration that occurs with an unlimited water supply.
-- Lysimeter
A device used to measure the amount of water lost through evapotranspiration.
-- Water Balance Method
A method of estimating evapotranspiration based on the continuity equation using precipitation, runoff, deep percolation, and soil water storage changes.
-- Crop Coefficient (Kc)
A factor that accounts for the specific crop's water use compared to reference evapotranspiration.

Additional Learning Materials

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