HYDROLOGY (GROUP 3)

BASED ON QUIZ 3

Evaporation

What is the process by which water is converted from liquid to vapor?

Philippines

Which present-day country is known for its tropical islands with high humidity?

1210 mm

What is the standard diameter of a Class A Evaporation Pan in mm?

Temperature, Wind Speed, Humidity

Give three factors affecting evaporation.

Solar Energy

What is the primary energy source for evaporation?

• Class A Evaporation Pan

• ISI Standard Pan

• Colorado Sunken Pan

• USGS Floating Pan

Four (4) types of evaporation pans.

0.7

What is the pan coefficient for a Class A Land Pan?

460 mm

What is the depth of a Colorado Sunken Pan in mm?

• Transformation

• Atmospheric Moisture

• Cloud Formation

• Precipitation

Give one role of evaporation in the water cycle.

Evaporation

is the process by which water is converted from its liquid form to its vapor form and thus transferred from land and water masses to the atmosphere.

Temperature

The rate of evaporation is directly dependent on the temperature it's exposed to. The more the temperature, the more liquid it's exposed to.

Surface Area of the Liquid

The rate of evaporation is directly dependent on the area the liquid is exposed to.

Humidity of the Air

Evaporation depends greatly on the water vapor present in the air. The lesser the water vapor, the quicker the cloth gets dried.

Wind Speed

The more the wind blows, the greater is the rate of evaporation

Intermolecular Attraction

The viscosity of elements or compounds often affects the rate of evaporation.

Vapor Pressure Difference

The rate of evaporation clearly depends on the vapor pressure of the air or the rate at which the air leaves the surface.

Atmospheric Pressure

• It was noticed that places on earth where the atmospheric pressure is lesser, the process of evaporation is more.

• Thus the more the atmospheric pressure, the lesser is the rate of evaporation.

Depth of the body (of water) where Evaporation occurs.

• The water body from where the water is evaporated is the main factor in how evaporation occurs.

• Thus, if the depth of a pond is too much, the rate at which the water will be evaporated will be more.

Presence of Solute in Solution

When salt is present inside water, the rate of evaporation increases.

Influence of Magnetic Field in Evaporation

• The influence of the magnetic field affects the rate of evaporation.

• The magnetic field affects the viscosity of the liquid and increases water tension.

Class A Evaporation Pan

It is a standard pan of 1210 mm diameter and 255 mm depth used by the US Weather Bureau.

ISI Standard Pan

• Also known as modified class A pan, consist of a pan 1220 mm in diameter with 255 mm of depth. the pan is made of copper sheet of 0.9 mm thickness, thinned inside and painted white outside.

• The evaporation at this pan is found to be less by about 14% to that from unscreened pan

Colorado Sunken Pan

This pan, 920 mm square and 460 mm deep is made up of unpainted galvanized iron sheet and buried into the ground within 100 mm of the top.

US Geological Survey Floating Pan

With a view to stimulate the characteristics of a large body of water, this square pan (900mm side and 450mm depth) supported by drum floats in the middle of a raft (4.25m x 4.87mis set afloat in a lake.

0.8

What is the pan coefficient of ISI Standard Pan?

0.78

What is the pan coefficient of Colorado Sunken Pan?

0.8

What is the pan coefficient of USGS Floating Pan?

Empirical Formulas

are mathematical equations derived from experimental data rather than theoretical principles.

1. Water Resource Management

2. Agriculture

3. Meteorology and Climate Studies

4. Engineering Projects

5. Hydrology

What are the Five (5) Uses of Empirical Evaporation Formulas?

Dalton’s Law of Evaporation

These empirical formulas for evaporation were largely influenced by ________________, which was first proposed by John Dalton in the early 19th century.

1. Fitzgerald’s Equation

2. Meyer’s Equation

3. Rohwer’s Equation

4. Horton’s Equation

5. Lake Mead’s Equation

Give the Five (5) Empirical Formulas

Fitzgerald’s Equation

Moderate – Works well in general but lacks temperature correction.

Meyer’s Equation

Moderate to High – Common in engineering applications.

Rohwer’s Equation

High – More precise because it includes atmospheric pressure effects.

Horton’s Equation

Moderate – Similar to Fitzgerald’s but with an exponential wind function

Lake Mead’s Equation

High – Best for locations where air-water temperature difference is important.

Water Budget Method

• also known as the Storage Equation

• estimates evaporation (E) from a reservoir or water body by balancing all the inflows and outflows, along with changes in storage.

Energy Budget Method

This method is based on the application "of the law of the conservation of Energy in the form of heat".