The following file contains contents regarding Evaporation. Different methods to measure evaporations.
Primarily three methods are mentioned to measure Evaporation, that is Empirical Methods, Analytical Methods, and By using Evaporimeter or Pan.
This presentation will provide the knowledge on measurement of evaporation by using class A evaporation pan. In addition it will give you the knowledge regarding pan coefficient and crop coefficient.
This presentation will provide the knowledge on measurement of evaporation by using class A evaporation pan. In addition it will give you the knowledge regarding pan coefficient and crop coefficient.
Stream flow representing the runoff phase of the hydrologic cycle is the most important basic data for hydrologic studies. Runoff is generated by rainstorms. Its occurrence and quantity are dependent on the characteristics of the rainfall event, i.e. intensity, duration and distribution. This module highlights about runoff components of the hydrological cycle.
Evaporation Pan meter , Pan Evaporimeter
Advantages and Disadvantages of Pan Evaporimeter.
Power point presentation for project description with summery.
Classification for pan evaporimeter.
Methods of Evaporation measurements
Dalton’s law of evaporation
The rate of evaporation depends upon the difference between the saturation vapour pressure in the air above
E= C(es-ea)
where c – coefficient depends upon barometric pressure
Es – saturation vapour pressure
Ea - Vapour pressure above 2 m height of water
Factors affecting
Temperature
Wind velocity
Atmospheric pressure
Nature of evaporating surface
Depth of water supply
Impurities in water
Energy budget method
LOW OF CONSERVATION of energy
Energy required is estimated by incoming outgoing, and stored energy in a specific time period
Total energy received from suns radiation = energy reflected + change in energy + energy required for evaporation
Energy budget method
most accurate method (evaporation is a function of the energy state of the water system)
difficult to evaluate all terms
energy balance equation has to be simplified
empirical formulas are used (although radiation measurements are preferable)
Water budget method
Characteristics:
Simple
Difficult to estimate Qd and Qs
Unreliable, accuracy will increase as Δt increases
Measurement et -
Direct measurement –
1 . Tank & lysimeter method
2. Field experimental method- no runoff no percolation
3. Soil moisture studies – gw deep
4. Integration method – laege area
5. Inflow and outflow studies
Infiltration rate
Infiltration capacity : The maximum rate at which, soil at a given time can absorb water.
f = fc when i ≥ fc
f = f 0when i < fc
where fc = infiltration capacity (cm/hr)
i = intensity of rainfall (cm/hr)
f = rate of infiltration (cm/hr)
Horton’s Formula:
This equation assumes an infinite water supply at the surface i.e., it assumes saturation conditions at the soil surface.
For measuring the infiltration capacity the following expression are used:
f(t) = fc + (f0 – fc) e–kt for
where k = decay constant ~ T-1
fc = final equilibrium infiltration capacity
f0 = initial infiltration capacity when t = 0
f(t) = infiltration capacity at any time t from start of the rainfall
td = duration of rainfall
Double Ring Infiltrometer
Infiltration indices The average value of infiltration is called infiltration index.
Two types of infiltration indices
φ – index (PHI INDEX)
w –index
PHI INDEX
- defined as average rate of rainfall such that excess volume of rainfall represents direct runoff
- unit is cm/hr or……
W INDEX
- average rate of loss (infiltration) averaged over whole storm period
- w index = P- Q- S
T
THUS phi index has to be some what than w index
IS 4987 - 1968
IN PLAINS – 520 km2
Elevation upto 1000 m – 260 to 390 km2
Hilly area – 130 km2
It is recommended that 10% of raingauge must be self recording type
Stream flow representing the runoff phase of the hydrologic cycle is the most important basic data for hydrologic studies. Runoff is generated by rainstorms. Its occurrence and quantity are dependent on the characteristics of the rainfall event, i.e. intensity, duration and distribution. This module highlights about runoff components of the hydrological cycle.
Evaporation Pan meter , Pan Evaporimeter
Advantages and Disadvantages of Pan Evaporimeter.
Power point presentation for project description with summery.
Classification for pan evaporimeter.
Methods of Evaporation measurements
Dalton’s law of evaporation
The rate of evaporation depends upon the difference between the saturation vapour pressure in the air above
E= C(es-ea)
where c – coefficient depends upon barometric pressure
Es – saturation vapour pressure
Ea - Vapour pressure above 2 m height of water
Factors affecting
Temperature
Wind velocity
Atmospheric pressure
Nature of evaporating surface
Depth of water supply
Impurities in water
Energy budget method
LOW OF CONSERVATION of energy
Energy required is estimated by incoming outgoing, and stored energy in a specific time period
Total energy received from suns radiation = energy reflected + change in energy + energy required for evaporation
Energy budget method
most accurate method (evaporation is a function of the energy state of the water system)
difficult to evaluate all terms
energy balance equation has to be simplified
empirical formulas are used (although radiation measurements are preferable)
Water budget method
Characteristics:
Simple
Difficult to estimate Qd and Qs
Unreliable, accuracy will increase as Δt increases
Measurement et -
Direct measurement –
1 . Tank & lysimeter method
2. Field experimental method- no runoff no percolation
3. Soil moisture studies – gw deep
4. Integration method – laege area
5. Inflow and outflow studies
Infiltration rate
Infiltration capacity : The maximum rate at which, soil at a given time can absorb water.
f = fc when i ≥ fc
f = f 0when i < fc
where fc = infiltration capacity (cm/hr)
i = intensity of rainfall (cm/hr)
f = rate of infiltration (cm/hr)
Horton’s Formula:
This equation assumes an infinite water supply at the surface i.e., it assumes saturation conditions at the soil surface.
For measuring the infiltration capacity the following expression are used:
f(t) = fc + (f0 – fc) e–kt for
where k = decay constant ~ T-1
fc = final equilibrium infiltration capacity
f0 = initial infiltration capacity when t = 0
f(t) = infiltration capacity at any time t from start of the rainfall
td = duration of rainfall
Double Ring Infiltrometer
Infiltration indices The average value of infiltration is called infiltration index.
Two types of infiltration indices
φ – index (PHI INDEX)
w –index
PHI INDEX
- defined as average rate of rainfall such that excess volume of rainfall represents direct runoff
- unit is cm/hr or……
W INDEX
- average rate of loss (infiltration) averaged over whole storm period
- w index = P- Q- S
T
THUS phi index has to be some what than w index
IS 4987 - 1968
IN PLAINS – 520 km2
Elevation upto 1000 m – 260 to 390 km2
Hilly area – 130 km2
It is recommended that 10% of raingauge must be self recording type
Evaporation is a process by which water changed from the liquid or solid state into the gaseous state through the absorption of heat
It is always related to the loss of water from a free surface over a fixed time interval. Either direct observation or calculation based on the factors involved in the transfer of thermal energy.
One of the fundamental component of hydrological cycle
Essential requirements in the process are
The source of energy to vaporize the liquid water (solar or wind)
The presence of gradient of concentration between the evaporating surface and the surrounding air.
Building Foundations, Soil Survey, Types of FoundationsAsmarudDin
A very brief and clear introduction to Foundation and its types along with soil investigation are provided. After studying you will be able to understand different types of Foundations and footings. Also various methods and techniques for soil investigation along with various types of soil according to the Building code of Pakistan.
Site Selection, Orientation and Ventilation Of BuildingAsmarudDin
The pdf file contains detailed information about Site selection, Orientation and Ventilation of a Building. After studying thoroughly you will grasp the concept behind the Site selection, Orientation and Ventilation of Building.
The Presentation contains a detailed description of buildings, their types, and various components of buildings. After studying you will be able to understand the Standard definition of buildings, classification of buildings on a different basis, and also components of buildings.
GIS & REMOTE sensing is very important for engineering. They are used widely for solutions to Real-world problems and also help in planning for the future.
In case of civil engineering it is in almost all disciplines of civil engineering .eg.
1. In transportation engineering used in finding best possible route
2. In earthquake engineering it is used to find the focus of the earthquake.
3. While making a survey it is very useful and RS is the heart of Aerial Surveying because without remote sensing Aerial surveying is incomplete.
4. Most importantly GIS helps us in disaster management.
Forklift Classes Overview by Intella PartsIntella Parts
Discover the different forklift classes and their specific applications. Learn how to choose the right forklift for your needs to ensure safety, efficiency, and compliance in your operations.
For more technical information, visit our website https://intellaparts.com
Quality defects in TMT Bars, Possible causes and Potential Solutions.PrashantGoswami42
Maintaining high-quality standards in the production of TMT bars is crucial for ensuring structural integrity in construction. Addressing common defects through careful monitoring, standardized processes, and advanced technology can significantly improve the quality of TMT bars. Continuous training and adherence to quality control measures will also play a pivotal role in minimizing these defects.
Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
Automobile Management System Project Report.pdfKamal Acharya
The proposed project is developed to manage the automobile in the automobile dealer company. The main module in this project is login, automobile management, customer management, sales, complaints and reports. The first module is the login. The automobile showroom owner should login to the project for usage. The username and password are verified and if it is correct, next form opens. If the username and password are not correct, it shows the error message.
When a customer search for a automobile, if the automobile is available, they will be taken to a page that shows the details of the automobile including automobile name, automobile ID, quantity, price etc. “Automobile Management System” is useful for maintaining automobiles, customers effectively and hence helps for establishing good relation between customer and automobile organization. It contains various customized modules for effectively maintaining automobiles and stock information accurately and safely.
When the automobile is sold to the customer, stock will be reduced automatically. When a new purchase is made, stock will be increased automatically. While selecting automobiles for sale, the proposed software will automatically check for total number of available stock of that particular item, if the total stock of that particular item is less than 5, software will notify the user to purchase the particular item.
Also when the user tries to sale items which are not in stock, the system will prompt the user that the stock is not enough. Customers of this system can search for a automobile; can purchase a automobile easily by selecting fast. On the other hand the stock of automobiles can be maintained perfectly by the automobile shop manager overcoming the drawbacks of existing system.
Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two type of water scarcity. One is physical. The other is economic water scarcity.
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
In this month's edition, along with this month's industry news to celebrate the 13 years since the group was created we have articles including
A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
Democratizing Fuzzing at Scale by Abhishek Aryaabh.arya
Presented at NUS: Fuzzing and Software Security Summer School 2024
This keynote talks about the democratization of fuzzing at scale, highlighting the collaboration between open source communities, academia, and industry to advance the field of fuzzing. It delves into the history of fuzzing, the development of scalable fuzzing platforms, and the empowerment of community-driven research. The talk will further discuss recent advancements leveraging AI/ML and offer insights into the future evolution of the fuzzing landscape.
Hybrid optimization of pumped hydro system and solar- Engr. Abdul-Azeez.pdffxintegritypublishin
Advancements in technology unveil a myriad of electrical and electronic breakthroughs geared towards efficiently harnessing limited resources to meet human energy demands. The optimization of hybrid solar PV panels and pumped hydro energy supply systems plays a pivotal role in utilizing natural resources effectively. This initiative not only benefits humanity but also fosters environmental sustainability. The study investigated the design optimization of these hybrid systems, focusing on understanding solar radiation patterns, identifying geographical influences on solar radiation, formulating a mathematical model for system optimization, and determining the optimal configuration of PV panels and pumped hydro storage. Through a comparative analysis approach and eight weeks of data collection, the study addressed key research questions related to solar radiation patterns and optimal system design. The findings highlighted regions with heightened solar radiation levels, showcasing substantial potential for power generation and emphasizing the system's efficiency. Optimizing system design significantly boosted power generation, promoted renewable energy utilization, and enhanced energy storage capacity. The study underscored the benefits of optimizing hybrid solar PV panels and pumped hydro energy supply systems for sustainable energy usage. Optimizing the design of solar PV panels and pumped hydro energy supply systems as examined across diverse climatic conditions in a developing country, not only enhances power generation but also improves the integration of renewable energy sources and boosts energy storage capacities, particularly beneficial for less economically prosperous regions. Additionally, the study provides valuable insights for advancing energy research in economically viable areas. Recommendations included conducting site-specific assessments, utilizing advanced modeling tools, implementing regular maintenance protocols, and enhancing communication among system components.
About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
1. Civil Engineering Department, University of Engineering and
Technology Peshawar
CE-431
Engineering Hydrology
Presented By
Asmar ud Din
ceasmar163@gmail.com
“EVAPORATION”
2. How Evaporation Occurs
Before rainfall reaches the outlet of a basin as runoff, certain demands of the
catchment such as interception, depression storage, and infiltration must be met.
Besides these, evaporation and transpiration processes transfer water to the
atmosphere as water vapor. Evaporation from water bodies and the soil mass together
with transpiration from vegetation is called evapotranspiration (ET). That portion of
Precipitation that is not available as surface runoff is termed “loss”.
3. Evaporation
Evaporation is the process in which a liquid changes to the gaseous state as the free
surface, below its boiling point, through the transfer of energy. Evaporation is a
cooling process- the latent heat of vaporization (~585 cal/g of evaporated water)
must be provided by the water body.
4. Factors Affecting Evaporation
The rate of evaporation depends on
Vapour pressure
Temperature
Wind speed
Humidity
Soluble Salts
Surface Area
Depth of Storage
5. Vapour Pressure
The rate of evaporation is proportional to the difference between the saturation
vapor pressure (SVP) at the water temperature ew and the actual vapor pressure in
the air ea.
EL = C (ew – ea )
Here
EL = Rate of Evaporation(mm/day)
C = constant
ew and ea are in mm of Hg
6. Temperature
The rate of evaporation increases with an increase in water temperature. Although
there is an increase in the rate of evaporation with an increase in air temperature, a
high correlation does not exist between them. For the same mean monthly
temperature, evaporation from a lake may be different in different months.
0
50
100
150
200
250
300
350
400
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Evaporation
Temperature(K)
Evaporation vs Temperature
7. Wind
The rate of evaporation increases with an increase in wind velocity up to
some limit (critical wind speed) and thereafter any further increase in
wind velocity does not have any effect on the evaporation rates.
0
50
100
150
200
250
0 5 10 15 20 25 30 35
Evaporation
Wind
Wind Vs Evaporation Asmar
8. Humidity
The rate of evaporation decreases with an increase in humidity. The lower the
relative humidity, the drier the air, and the higher the evaporation rate. The more
humid the air, the closer the air is to saturation, and less evaporation can occur.
9. Soluble Salts
When a solute is dissolved in water, the vapor pressure of the solution is less than
that of pure water and hence it causes a reduction in the rate of evaporation. The
percentage reduction in the evaporation rate approximately corresponds to the
percentage increase in specific gravity. Under identical conditions evaporation from
seawater is about 2-3% less than that from freshwater.
10. Surface Area
Evaporation increases with an increase in the surface area.
If the surface area is increased, then the amount of liquid that is exposed to air is
larger. More molecules can escape with a wider surface area. For e.g. We spread out
clothes to dry. We do that because that speeds up the process of vaporization.
11. Depth of Storage
Deep water bodies have more heat storage capacity than shallow water bodies. A
deep lake stores radiation energy received in summer and releases it in winter
resulting in less evaporation in summer and more evaporation in winter when
compared to a shallow lake exposed to similar situations.
13. Evaporimeter
These are pans containing water that is exposed to the atmosphere. Loss of water by
evaporation from these pans is measured at regular intervals (daily). Meteorological
data such as humidity, wind velocity, air and water temperatures, and precipitation
are also measured and noted along with evaporation.
15. Class A Pan
A pan of diameter 1210mm and depth 255mm.
Depth of water is maintained between 18 and 20cm.
The pan is made of an unpainted GI sheet.
The pan is placed on a wooden platform of height 15cm above ground level to
allow free air circulation below the pan.
Evaporation is measured by measuring the depth of water in a stilling well with a
hook gauge.
16. ISI Standard Pan
A modified form of Class A pan.
A pan of diameter 1220mm and depth 255mm.
The pan is made of a copper sheet 0.9mm thick, tinned inside, and painted white
outside.
The pan is placed on a square wooden platform of width 1225mm and height
100mm above ground level to allow free air circulation below the pan.
A fixed-point gauge indicates the level of water.
17. Colorado Sunken Pan
920mm square pan made of unpainted GI sheet, 460mm deep, and buried into the
ground within 100mm of the top.
Main advantage of this pan – its aerodynamic and radiation characteristics are like
that of a lake.
Disadvantages – difficult to detect leaks, expensive to install, extra care is needed
to keep the surrounding area free from tall grass, dust etc.
18. Pan Coefficient (Cp)
Evaporation pans are not exact models of large reservoirs. Their major drawbacks
are the following:
They differ from reservoirs in the heat storage capacity and heat transfer
characteristics from the sides and the bottom.
The height of the rim in an evaporation pan affects wind action over the water
surface in the pan.
Also, it casts a shadow of varying sizes on the water’s surface.
The heat transfer characteristics of the pan material are different from that of a
reservoir.
Hence evaporation measured from a pan must be corrected to get the evaporation
from a large lake under identical climatic and exposure conditions
19. Pan Coefficient (Cp)
Mathematically,
(Evaporation)site = Pan Coefficient × (Evaporation)pan
or
Pan Coefficient = Cp =
(Evaporation)site
(Evaporation)pan
The value of the pan coefficient is different for different pan types as given below.
S.No Pan Type Pan Coefficient
1 Class A 0.7
2 ISI Standard 0.8
3 Colorado Sunken 0.78
4 US Geological Survey Floating Pan 0.8
20. Evaporation Station
World Meteorological Organization (WMO) suggests the following minimum
number of Evaporimeters for a particular area.
For Arid Zone one station per 30,000 km2 is enough.
For the Humid zone one station per 50,000 km2 is a suitable option.
For Cold Zone one station per 100,000km2 is required.
21. Empirical Methods/Equations
Most of the available empirical equations for estimating lake evaporation are
Dalton-type equations of the general form.
EL = K F (u) (ew – ea )
Here,
EL = Evaporation (mm/day)
K =Constant
F(u)= Wind speed correction function
ew = Saturation vapour pressure at the water surface temp:
ea = Actual vapour pressure of overlaying air at a specified height
22. Empirical Methods/Equations
We will discuss only two empirical equations or empirical formulae.
Meyer’s Equation/Formula
Rohwer’s Equation/Formula
QuizTime
what could be the disadvantages of
Colorado Sunken Pan?
23. Meyer’s Equation/Formula
Meyer’s formula/equation for calculating evaporation is given below.
EL = Km (ew – ea) (1+
U9
𝟏𝟔
)
Here,
EL = Lake Evaporation (mm/day)
Km = Meyer’s constant
Normally for deep lakes Km = 0.36 and for Shallow lakes Km = 0.5
ew = Saturation vapor pressure at water surface temp:
ea = Actual vapour pressure of overlaying air at a specified height
U9 = Monthly Mean Velocity(km/hr) at 9m above ground
24. Rohwer’s Equation/Formula
Rohwer’s formula/equation for calculating evaporation is given below.
EL = 0.771(1.465-0.000732Pa)(ew- ea)(0.44-0.0733uo)
Here
EL = Lake Evaporation (mm/day)
Po = Mean barometric reading in mm of Hg
Uo = Monthly mean velocity (km/hr) at ground level
Note:( Important)
Uh = Ch1/7
C = constant
Uh = Wind velocity at height ‘h’
25. Analytical Methods/Equations
We can also estimate the Evaporation by using analytical methods. Two
of the most common analytical methods are.
Water Budget Equation
Energy Budget Equation
26. Water Budget Equation/Formula
The formula or equation for the water budget method is given below.
We know that
∆S = Inflow - Outflow
∆S = (P + VIG + VIS ) – (VOS + VOG + EL + TL )
Here
∆S = Change in Storage
P = Precipitation
VIS = Surface inflow to the lake
VOS = Surface outflow to the lake
VIG = Groundwater inflow to the lake
VOS = Groundwater outflow from the lake
TL = Transpiration loss
EL = Evaporation
27. Energy Budget Equation/Formula
The formula or equation for the Energy budget method is given below.
EL =
Hn –Hs –Hi –Hg
ρ(𝟏 β
Here
Hn =Net heat received by water surface, Hn = Hc (1-γ)-HB
Hb = Back Radiations
He = Heat used up in evaporation
Hg = Heat flux into the ground
Ha = Sensible heat transfer from water to air
Hi = Net heat going out of a system by water flow
Hs = Net Heat Stored in water