Hydrology & Water Resources Engineering - Vol 2 | 21. Evapotranspiration Equations: Penman and Blaney & Criddle Methods by Abraham | Learn Smarter
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21. Evapotranspiration Equations: Penman and Blaney & Criddle Methods

Evapotranspiration is a crucial process in the hydrological cycle, combining evaporation and transpiration, significantly influencing water resource management. The Penman and Blaney & Criddle methods are key techniques for estimating evapotranspiration, with distinct applications based on data availability and climate conditions. Understanding these methods is essential for effective irrigation scheduling, water resource planning, and hydrological modeling.

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Sections

  • 21

    Evapotranspiration Equations: Penman And Blaney & Criddle Methods

    This section covers the essential concepts of evapotranspiration (ET) and introduces the Penman and Blaney & Criddle methods for estimating ET.

    Learning Practice

  • 21.1

    Concept Of Evapotranspiration

    Evapotranspiration (ET) is the combined process of evaporation and transpiration, essential for understanding water loss in hydrological systems.

    Learning Practice

  • 21.2

    Penman Method

    The Penman Method estimates potential evapotranspiration (PET) using a combination of energy balance and aerodynamic principles.

    Learning Practice

  • 21.2.1

    Introduction To Penman Equation

    The Penman Equation estimates potential evapotranspiration (PET) using energy balance and aerodynamic principles, making it essential for accurate water resource management.

    Learning Practice

  • 21.2.2

    Components Of Penman Equation

    This section details the key components of the Penman Equation used for estimating potential evapotranspiration (PET), specifically net radiation, aerodynamic terms, and temperature/vapor pressure parameters.

    Learning Practice

  • 21.2.2.a

    Net Radiation (Rn)

    Net Radiation (Rn) is the balance of incoming and outgoing radiation at a crop surface and is crucial for estimating potential evapotranspiration.

    Learning Practice

  • 21.2.2.b

    Aerodynamic Term

    The aerodynamic term plays a crucial role in the Penman equation for estimating potential evapotranspiration, accounting for wind speed and vapor pressure deficits.

    Learning Practice

  • 21.2.2.c

    Temperature And Vapor Pressure Parameters

    This section discusses the computation of saturation vapor pressure and actual vapor pressure in relation to temperature and humidity.

    Learning Practice

  • 21.2.3

    Advantages And Limitations Of Penman Method

    The Penman Method for estimating potential evapotranspiration (PET) has significant advantages, including its accuracy under varied conditions, yet it also presents limitations such as the requirement for detailed meteorological data.

    Learning Practice

  • 21.3

    Blaney And Criddle Method

    The Blaney and Criddle method is an empirical approach for estimating crop evapotranspiration based on temperature and daylight hours.

    Learning Practice

  • 21.3.1

    Introduction

    The Blaney and Criddle method estimates seasonal crop evapotranspiration using temperature and daylight hours, making it suitable for regions with limited climatic data.

    Learning Practice

  • 21.3.2

    Blaney And Criddle Equation

    The Blaney and Criddle Equation estimates crop evapotranspiration based on temperature and daylight hours.

    Learning Practice

  • 21.3.3

    Calculation Of The P Factor

    The p factor is crucial for estimating crop evapotranspiration in the Blaney and Criddle method, calculated based on daylight hours and monthly considerations.

    Learning Practice

  • 21.3.4

    Crop Coefficient (K)

    The crop coefficient (k) is a dimensionless value that varies based on crop type, growth stage, and climatic zone, essential for calculating evapotranspiration.

    Learning Practice

  • 21.3.5

    Limitations Of Blaney And Criddle Method

    The Blaney and Criddle method has significant limitations, including its inability to consider humidity, wind speed, or radiation, making it less accurate in regions with high climatic variability.

    Learning Practice

  • 21.4

    Comparison Of Penman And Blaney & Criddle Methods

    This section provides a comparison between the Penman and Blaney & Criddle methods for estimating evapotranspiration, highlighting their differences in approach, data requirements, and applicability.

    Learning Practice

  • 21.5

    Applications In Civil Engineering

    This section discusses the key applications of evapotranspiration methods in civil engineering, focusing on their importance in irrigation scheduling, water resource planning, urban hydrology, climate impact studies, and drought analysis.

    Learning Practice

References

Chapter_21_Evapo.pdf

Class Notes

Memorization

What we have learnt

  • Evapotranspiration is the t...
  • The Penman Method combines ...
  • The Blaney & Criddle Method...

Final Test

Revision Tests