2. – Crop water requirements are a critical aspect of
irrigation management, as they determine the
amount of water a crop needs to grow and produce
high yields
– The accurate determination of crop water
requirements is essential for effective and efficient
irrigation practices, and has far-reaching
implications for both agricultural production and
water resource management
– One of the key benefits of determining crop water
requirements is that it helps to ensure optimal crop
growth
– Another important aspect of crop water
requirements is water conservation
3. – Accurately determining crop water requirements
helps to reduce water waste by avoiding
overwatering or underwatering of crops, which
can lead to the loss of water through
evaporation or runoff, respectively
– Determining crop water requirements is critical
for planning and managing irrigation systems
– However, the method requires a significant
amount of data and can be time-consuming to
calculate, which can limit its practicality for some
users
4. Climate change impact on
crop water requirements
– Climate change is expected to have significant
impacts on crop water requirements, both in
terms of the amount and timing of water
needed for crop growth
– These impacts will vary depending on the
location, crop type, and climate scenario, but
some general trends can be identified
– One of the most significant impacts of climate
change on crop water requirements is an
increase in evapotranspiration rates due to
higher temperatures
– Another impact of climate change on crop
water requirements is changes in precipitation
patterns
– Changes in the timing and intensity of extreme
weather events, such as heat waves and
heavy rainfall, can also have significant
impacts on crop water requirements
5. Climate change impact on
crop water requirements
– Weather variation and climate change
continue to have an impact on delicate eco-
regions, such as the Indian Hot Arid Zone,
which has a high density of people and
animals and is heavily dependent on
climatically vulnerable industries like
agriculture and animal husbandry
– According to the IPCC's fifth assessment
report, climate change is expected to
significantly impact crop water requirements
6. Methodologies
for ET
Estimation
– There are several methods for
estimating evapotranspiration , which
is the process of water loss from the
soil surface, plants, and surrounding
atmosphere
– These methods include
– 2) Soil Water Balance 3)Crop
Coefficient 4) Remote Sensing
Method 5)Penman-Monteith Method
6) Blaney-Criddle Method
7)Thornthwaite Method 8)Turc Method
9) Hargreaves Method
7. Eddy
Covariance
– The Eddy Covariance approach for ET estimation,
the eddy covariance method is frequently used to
verify the outcomes of other ET estimate methods
– Because to the specific equipment and expertise
needed to apply the EC technique, this study
relies on the EC ET estimations for validation of
the outcomes of the other methods rather than as
a possible suggestion for wider implementation
– Latent heat flux is measured by the EC technique
as the covariance between vertical wind speed
and water vapour density over a footprint area
8. Soil Water
Balance
Soil Water Balance is a simple and widely
used method for estimating
evapotranspiration
It involves monitoring the soil moisture
content over time to estimate the amount
of water lost through evapotranspiration
Soil Water Balance was first introduced in
the early 1900s by Thornthwaite
9. Crop
Coefficient
– The crop coefficient method has been
shown to reliably estimate ET for
irrigation scheduling purposes
– The Kc method relies on the
correlation between reference ET and
actual ET at different stages in crop
development to estimate ETa
– The Kc method estimates actual ET
using the following equation ETpm is
defined as the ET rate of an idealized
reference crop that is not
waterstressed
10. Remote
Sensing
Method
– Remote Sensing Method is a technique used for
estimating evapotranspiration by measuring and
analyzing the electromagnetic radiation reflected
or emitted by the Earth's surface using remote
sensors
– The method utilizes satellite-based sensors, such
as the Moderate Resolution Imaging
Spectroradiometer and Landsat, to obtain data on
surface temperature, vegetation indices, and other
environmental variables that are used to estimate
ET
– The Remote Sensing Method is based on the
principle that the energy emitted by the Earth's
surface is proportional to the surface temperature
and vegetation cover, which are indicators of ET
11. The Penman-
Monteith method
– The Penman-Monteith method is one of the most
widely used methods for estimating
evapotranspiration
– It is considered as a standard method for
calculating reference evapotranspiration , which is
the amount of water that would be evaporated or
transpired by a hypothetical grass crop under
standard climatic conditions
– The method takes into account the effect of both
the energy balance and the aerodynamic
resistance, and is recommended by the Food and
Agriculture Organization of the United Nations for
use in crop water requirements estimation
12. Blaney-
Criddle
Method
The Blaney-Criddle Method is a widely used empirical
method for estimating reference evapotranspiration
The equation for the Blaney-Criddle Method is given as:
where ETo is the reference evapotranspiration in
mm/day, H is the number of daylight hours in the day,
and tmean is the average daily temperature in °C
The method was developed by Blaney and Criddle in
1950 and is widely used due to its simplicity and the
ease of obtaining the required input data
13. Thornthwaite
Method
The Thornthwaite Method is an empirical method
for estimating potential evapotranspiration based
on monthly mean temperature data
The method was developed by C.W
The Thornthwaite Method is easy to use and
requires only monthly temperature data
14. Turc
Method
The Turc method is an empirical method used for
estimating potential evapotranspiration based on
temperature data
It is a relatively simple method that does not
require any additional weather data beyond
temperature, making it particularly useful in
regions where data availability is limited
The method was developed by Turc in 1961 and
is commonly used in arid and semi-arid regions
15. Hargreaves
Method
– The Hargreaves Method is an
empirical method used for estimating
reference evapotranspiration
– The Hargreaves Method uses
temperature data to estimate the solar
radiation received by the earth's
surface
– The Hargreaves Method has been
shown to provide good estimates of
reference evapotranspiration when
compared to more complex methods
like the Penman-Monteith Method
16. Jensen-
Haise
Method
The Jensen-Haise Method is an empirical
method for estimating potential
evapotranspiration
The JH method is based on the principle that
PET is proportional to the net radiation, and is
also influenced by the air temperature and
humidity
The JH method is suitable for areas with high
humidity and moderate temperatures, and can be
used for both short-term and long-term PET
estimations
17. Priestley-
Taylor
Method
The Priestley-Taylor method is an empirical
method for estimating evapotranspiration based
on the energy balance equation
This method uses only net radiation and air
temperature data to estimate ET
The Priestley-Taylor coefficient is a
dimensionless parameter that varies between 0
and 2, with values typically ranging from 1.2 to
1.5 for different land surfaces
18. Abtew Method
– The Abtew Method is an empirical
method developed to estimate
daily reference evapotranspiration
– It was developed by Alemu Abtew
in 1999 for use in the United
States
– The Abtew Method has been
found to be a reliable method for
estimating reference
evapotranspiration in many
regions of the United States
19. Advancement of Machine
Learning Models to estimate
crop water requirements
– The use of advanced machine learning
models for estimating crop water
requirements has been growing in
popularity in recent years due to their many
advantages over traditional methods
– One of the main advantages of advanced
machine learning models is their increased
accuracy
– Another advantage of advanced machine
learning models is that they can provide
real-time predictions of crop water
requirements
20. Potential
Evapotranspirati
on estimation for
Indian conditions
The potential evapotranspiration estimation equation used for a
particular region should be suitable for the climatic and environmental
conditions of that region
India is a vast country with diverse climatic conditions ranging from
humid tropical to arid regions, which makes it necessary to use an
equation suitable for the specific conditions
The Penman-Monteith equation is considered the most suitable
method for estimating PET in India
The study was carried out in the state of Telangana, India, where
daily weather data such as maximum and minimum temperatures,
wind speed, and relative humidity were collected for the years 2010
21. Potential Evapotranspiration
estimation for Indian
conditions
– The six empirical methods
considered in the study
were the Penman-Monteith
method, Hargreaves
method, Priestley-Taylor
method, Jensen-Haise
method, Turc method, and
the Blaney-Criddle method
22. Irrigation Scheduling
Using
Evapotranspiration
– Irrigation schedules can be done
based on evapotranspiration by using
an irrigation scheduling method called
the ET-based approach
– The first step in an ET-based irrigation
schedule is to measure actual ET
rates using an ET weather station or
other ET measurement tools
– The ET-based irrigation schedule can
be adjusted based on factors such as
soil moisture levels, rainfall, and crop
growth stage
23. Recent
advancemen
t in
estimation of
crop water
requirement
Based on the objectives of the study, mainly four
different sections of crop water requirement study
was explored which includes
2) Recent advancement in Different irrigation
system
3) Advancement in irrigation system for Tomato
24. Methods for
Estimating the
PET
– Pandey et al. : This study aimed to identify a suitable
alternative to the FAO-56 Penman-Monteith equation for
calculating reference evapotranspiration from chosen
temperature and radiation-based models utilizing monthly
meteorological data from 30 destinations in diverse agro-
ecological regions of the Northeast India i.e., Assam Bengal
Plain , eastern Himalaya , and the northeastern hilly region
– The study concluded that radiation-based IRMAK3 was
most appropriate in the ABP region
– The study area was located in the Bhadarabad region of
Hardwar district in Uttaranchal State, India
– The study concluded that using geomatic tools the irrigation
water requirement is less to the tune of 83.93 ha mm
25. Methods for
Estimating the
PET
– The authors evaluated the performance of
these methods using data from 330
weather stations around the world, covering
a wide range of Köppen climate classes
– The authors found that the Hargreaves-
Samani method performed the best overall,
with the lowest error in estimating
evapotranspiration across all Köppen
climate classes
– Brown et al. used simulated annealing for
on-farm irrigation scheduling considering
seasonal water limits
26. Recent advancement
in Different irrigation
system
– Kadbhane and Manekar : This study is about the
Agro-Hydrological Evaluation of Farm Pond for
Supplemental Irrigation in Nashik District, India
– The study looks at the potential of farm ponds to
provide supplemental irrigation in the Nashik
District of India, and evaluates their feasibility from
an agro-hydrological perspective
– The study begins by providing a brief overview of
the water resources of the Nashik District, and
then examines the potential of farm ponds for
providing supplemental irrigation
– Kadbhane and Manekar : This paper presents an
experimental study that looked at the effects of
two different irrigation systems on a grape orchard
in India
27. Recent advancement
in Different irrigation
system
– The authors discuss how
evapotranspiration is an important
process in the hydrological cycle and
affects the availability of water
resources
– The authors conclude that using GIS
and remote sensing for estimating pan
evaporation and actual
evapotranspiration is a viable and
cost-effective option for water
resource development in India
28. Advancement in
irrigation system for
Tomato
– Singh et al. : This paper examines the effects of
drip irrigation and black polyethylene mulch on the
growth, yield and water-use efficiency of tomatoes
– The study was conducted in an experimental field
in India, where the tomatoes were grown with drip
irrigation and without drip irrigation, with or without
black polyethylene mulch
– The results of the study showed that the tomatoes
grown with drip irrigation and black polyethylene
mulch had a higher yield and higher water-use
efficiency than those grown without drip irrigation
and without black polyethylene mulch
– The study concluded that drip irrigation and black
polyethylene mulch can be used to increase
tomato yields and water-use efficiency
29. Advancement in
irrigation system for
Tomato
– The researchers tested
different irrigation
scheduling and fertigation
regimes on a tomato crop
over a period of five years
30. Impact of Climate
Change on
Agriculture
– Arora : examines the impact of climate change on
agricultural production, and provides sustainable solutions
to mitigate the negative effects
– The author argues that climate change has had a major
impact on agricultural production, leading to a decrease in
crop yields and an increase in pest outbreaks
– The paper also identifies several sustainable solutions to
address these issues, such as using climate-smart
agricultural practices, investing in climate-resilient crops,
and promoting sustainable water and soil management
– The authors use a panel dataset from 31 provinces over the
period 2000-2015 to examine the impacts of climate change
on agricultural productivity in China
31. Impact of Climate
Change on
Agriculture
– The authors find that climate change has had negative
impacts on agricultural productivity in both the short and
long run
– The authors analyze the effects of climate change on crop
yields, water availability, and food security in the region
– The authors conclude that climate change is likely to have a
negative impact on agricultural productivity and food
security in the region, and suggest that policies to help
farmers adapt to climate change should be implemented
– The study uses data from a variety of sources including
existing studies, interviews with farmers and experts, and
surveys of local communities in order to identify and
analyze the various adaptation strategies
32. Author Year Objective Findings Conclusion
Pandey et al.
(2016)
2016 To identify a suitable alternative to the FAO-56 Penman-
Monteith equation for calculating reference
evapotranspiration (ET0) using temperature and
radiation-based models in diverse agro-ecological
regions of Northeast India
The radiation-based IRMAK3
model was found to be the most
appropriate in the Assam Bengal
Plain (ABP) region
The radiation-based IRMAK3
model can be used as an
alternative to the FAO-56
Penman-Monteith equation for
calculating ET0 in the ABP
region
Singh et al.
(2016)
2016 To evaluate irrigation scheduling using geomatics tools
and compare irrigation water requirements between
conventional and geomatics techniques in the
Bhadarabad region of Hardwar district, India
The use of geomatics tools
resulted in a reduction of
irrigation water requirement by
83.93 ha mm
Geomatics tools can effectively
optimize irrigation scheduling
and reduce water requirements
Almorox et al.
(2015)
2015 To compare the performance of five temperature-based
approaches for estimating evapotranspiration in different
climate classes
The Hargreaves-Samani method
performed the best overall in
estimating evapotranspiration
across all climate classes
The Hargreaves-Samani method
can be recommended for
estimating evapotranspiration in
different climate classes
Brown et al.
(2010)
2010 To optimize on-farm irrigation scheduling with a
seasonal water limit using simulated annealing and
maximize farm profit
Simulated annealing-based
optimization improved irrigation
scheduling and maximized farm
profit under seasonal water limits
Simulated annealing can be a
useful tool for optimizing on-farm
irrigation scheduling
Granata et al.
(2020)
2020 To examine the use of artificial intelligence-based
methods to estimate actual evapotranspiration in
wetlands
Artificial intelligence-based
methods using remote sensing
data and machine learning
algorithms accurately estimated
evapotranspiration in a wetland
Artificial intelligence-based
methods can be applied to
estimate evapotranspiration in
wetland environments
Important Literature on Methods for Estimating the PET
33. Recent advancement in Different irrigation system
Author Year Objective Findings Conclusion
Kadbhane and
Manekar (2013)
2013 Agro-Hydrological Evaluation of
Farm Pond for Supplemental
Irrigation in Nashik District, India
Farm ponds have the potential to
provide supplemental irrigation
in the Nashik District
Farm ponds could be a viable source of
supplemental irrigation in the Nashik
District
Kadbhane and
Manekar (2017)
2017 Experimental study comparing drip
irrigation and surface irrigation on
grape orchards in India
Drip irrigation was more effective
than surface irrigation in terms of
water utilization, soil moisture
conservation, and yield
Drip irrigation is a more efficient and
effective irrigation system for grape
orchards
Rathod and
Manekar (2017)
2017 Use of GIS and remote sensing to
estimate pan evaporation and actual
evapotranspiration in water resource
development in India
GIS and remote sensing are
viable and cost-effective options
for estimating evapotranspiration
in water resource development
Using GIS and remote sensing is a viable
and cost-effective option for water
resource development in India
Kaur & Sharma
(2022)
2022 Effects of different irrigation
management systems on rice
productivity and water use efficiency
in north-western India
Surface irrigation had the
greatest effect on rice
productivity and water use
efficiency, followed by sprinkler,
drip, sub-surface, and shallow
tube-well irrigation
Different irrigation management systems
can be used to increase rice productivity
and water use efficiency in north-western
India
Ghosh et al. (2010) 2010 Study of water user associations
(WUAs) and their role in managing
group dynamics under different
irrigation systems in an eastern
Indian state
WUAs can be effective in
managing group dynamics and
achieving consensus in water
resource management
The effectiveness of WUAs is influenced
by factors such as membership size, trust
among members, and presence of
external stakeholders
34. Advancement in irrigation system for Tomato
Author Year Objective Findings Conclusion
Singh et
al. (2009)
2009 Effects of drip irrigation and black
polyethylene mulch on tomatoes
Drip irrigation and black
polyethylene mulch increased
tomato yield and water-use
efficiency
Drip irrigation and black polyethylene
mulch can be used to increase tomato
yields and water-use efficiency
Gupta et
al. (2015)
2015 Potential of drip irrigation and
fertigation technology in hybrid
tomatoes
Drip irrigation and fertigation
technology can increase yields,
improve quality, and reduce water
and fertilizer use in hybrid
tomatoes
Drip irrigation and fertigation technology
offer potential benefits and should be
further researched and implemented
Singandh
upe et al.
(2003)
2003 Effects of fertigation and irrigation
scheduling on tomato crop yield in a
drip irrigation system
Proper irrigation scheduling and
fertigation can maximize tomato
crop yield
Irrigation scheduling and fertigation have
a significant impact on tomato crop yield
Kumar
and
Khanna
(2019)
2019 Comparative study of different
irrigation methods on tomato crop in
western Uttar Pradesh, India
Drip irrigation was the most
effective method, followed by
furrow irrigation, basin irrigation,
and traditional irrigation
Drip irrigation is the most suitable method
for tomato crop cultivation in western
Uttar Pradesh, India
35. Impact of Climate Change on Agriculture
Author Year Objective Findings Conclusion
Arora (2019) 2019 Impact of climate change on agricultural
production and sustainable solutions
Climate change negatively affects crop yields,
increases pest outbreaks. Sustainable solutions
include climate-smart agricultural practices,
resilient crops, and water and soil management.
Public policies and international cooperation are
essential.
Climate change negatively impacts agriculture, but
sustainable solutions and policies can mitigate its
effects.
Chandio et al.
(2020)
2020 Short and long-term impacts of climate
change on agriculture in China
Climate change negatively affects agricultural
productivity in China. Rising temperatures and
extreme weather events reduce yields, while
increased precipitation has a positive effect. Long-
term impacts are more pronounced. Mitigation
policies and technologies should be developed.
Climate change has negative impacts on agricultural
productivity in China, necessitating the development
of mitigation policies and technologies.
Bocchiola (2019) 2019 Impact of climate change on agricultural
productivity and food security in the
Himalayas
Climate change negatively affects crop yields,
water availability, and food security in the
Himalayas. Adaptations, such as new crop
varieties and increased irrigation, should be
implemented.
Climate change has a negative impact on agricultural
productivity and food security in the Himalayas.
Adaptation policies are crucial.
Aryal et al. (2020) 2020 Effects of climate change on agriculture
in South Asia and adaptation strategies
for smallholder farmers
Smallholder farmers need to adapt to mitigate
climate change effects. Various adaptation
strategies exist, but barriers such as resource
access and financial capability must be addressed.
More research is needed for better understanding
and appropriate adaptation strategies.
Smallholder farmers in South Asia should adopt
adaptation strategies to mitigate climate change
effects. Further research is necessary to develop
effective strategies.
Guntukula (2020) 2020 Impacts of climate change on Indian
agriculture, focusing on crop yields
Climate change negatively affects crop yields in
India, particularly in Punjab and Haryana.
Temperature and precipitation have the greatest
impact. Incentives for climate-smart agricultural
Climate change significantly reduces crop yields in
India, particularly in northern and central regions.
Incentives for climate-smart practices are necessary.
36. Research Gap
– Based on the above literature review fallowing points were observed and addressed in this study:
There is a need for accurate estimation of potential evapotranspiration (PET) in India due to the country's
reliance on agriculture and the need for efficient irrigation systems.
The use of empirical methods for PET estimation has limitations, such as the lack of representation of local
climatic conditions.
The Penman-Monteith method (PM) is considered the most accurate method for PET estimation, but it
requires extensive data input, which may be a challenge in data-scarce regions.
Remote sensing and machine learning techniques have shown potential for PET estimation, but there is a
need for further validation and comparison with traditional methods.
The impact of climate change on PET and crop water requirements is an important research gap that needs
to be addressed, given the potential effects on agricultural productivity and water resource management.
In addition to PET estimation, it is also observed that, there is need of scientific exploration of irrigation
method suitable for irrigation particularly in Maharashtra to have optimum usage of water.
37. Conclusion
• Estimating potential evapotranspiration is crucial for proper irrigation management,
especially in water-scarce regions like India.
• Various empirical and AI-based models are available for estimating potential
evapotranspiration.
• The accuracy of these models varies depending on climatic conditions and the availability of
input data.
• The Penman-Monteith method is considered the most accurate and reliable model for
estimating potential evapotranspiration.
• However, it requires extensive meteorological data and can be time-consuming to apply in
the field.
• There is a need to improve the accuracy of empirical models by calibrating coefficients and
improving input data quality.
• AI-based models like M5Tree and Random Forest should be explored further to enhance the
accuracy of potential evapotranspiration estimation.
• The development of more efficient irrigation systems should be promoted to reduce water
usage and ensure sustainable agriculture.
• The impact of climate change on agriculture should be considered in the development of
