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Advanced Hydrology(Web course)

Subhankar Karmakar

Assistant Professor

Centre for Environmental Science and Engineering (CESE)

Indian Institute of Technology Bombay

Powai, Mumbai 400 076

Email: skarmakar@iitb.ac.in

Ph. # +91 22 2576 7857

mailto:skarmakar@iitb.ac.inmailto:skarmakar@iitb.ac.in

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Hydrologic Cycle

Prof. Subhankar KarmakarIIT Bombay

Module 1

3 Lectures

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The objective of this module is to introduce the

phenomena of weather, different stages of the hydrologic

cycle, hydrologic losses and its measurements.

Module 1

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Topics to be covered

Weather

Introduction to Hydrology

Different stages of Hydrology or water cycle

Hydrologic losses and measurements

Analytical Methods

Empirical Methods

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Lecture 1: Weather and hydrologic cycle

Module 1

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Weather & Climate

Weather- the state of the atmosphere with respect to heat or cold, wetness

ordryness, calmorstorm, clearness or cloudiness.

Cl imate the average course or condition of the weather ata place usually

over a period of years as exhibited by temperature, wind velocity, and

precipitation.

(Wikipedia)

Weather refers, generally, to day-to-day temperature and precipitationactivity, whereas climate is the term for the average atmospheric conditionsover longer periods of time.

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Atmosphere

Troposphere

Most of the weather occurs.

Stratosphere

19% of the atmospheres gases;

Ozone layer

Mesosphere

Most meteorites burn up here.

Thermosphere

High energy rays from the sun areabsorbed;

Hottest layer.

Exosphere

Molecules from atmosphere

escape into space; satellites orbit here.(http://www.windows.ucar.edu/tour/link=/earth/Atmosphere/layers_activity_print.html) Module 1Lecture 1

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Winds and Wind belts

Exist to circulate heat and

moisture from areas of heating

to areas of coolingEquator to poles

Low altitudes to high

altitudes

Three bands of low and high

pressure above and below the

equator (area of low pressure)

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Cloud Types

Cloud is a visible set of drops of water and fragments of ice suspended inthe atmosphere and located atsome altitude above the earths surface.

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Classif ication of Precipitation events

Based on the mechanism by which air is lifted.

Frontal lifting:

Warmer air is forced to go above cooler air in equilibrium with a cooler surface.

Orographic lifting:

Air is forced to go over mountains (and its the reason why windward slopes

receive more precipitation).

Convective Lift ing:

Warm air rises from a warm surface and progressively cools down.

Cyclonic Lifting:

A cyclonic storm is a large, low pressure system that forms when a warm air

mass and a cold air mass collide.

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Frontal lifting

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Orographic lifting

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Convectional lifting

(climateofindia.pbworks.com)

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Cyclonic lifting

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Factors affecting Indian cl imate

Related to Locat ion and Rel ief Related to Air Pressure and Wind

Latitude

Al titude

Relief

Distance from Sea

The Himalayan Mountains

Distribut ion of Land & water

Surface pressure & wind

Upper air circulation

Western cyclones

Module 1

Factors affecting Indian climate

Lecture 1

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Seasons

Cold weather

Hot weather

South west monsoon

Retreating monsoon

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It extends from December toFebruary.

Vertical sun rays shift towardssouthernhemisphere.

North India experiencesintense cold

Light wind blow makes thisseason pleasant in south

India.

Occasional tropical cyclonevisit eastern coast in thisseason.

Tropical Cyclone

Cold Weather Season

Seasons

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250C

250C

200C

200

C

200C

150C

200C

100C`

Temperature-January

(climateofindia.pbworks.com)Module 1

Seasons

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Pressure-January

(climateofindia.pbworks.com)

1014

HIGHPRESSURE

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Seasons

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RAINFALL DUE

TO WESTERN

DISTURBANCES

RAINFALL DUE

TO NORTH EAST

WIND

Winter Rainfall

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Seasons

Lecture 1

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It extends from March toMay.

Vertical sun rays shifttowards Northern

hemisphere.

Temperature rises graduallyfrom south to north.

Highest Temperature

experiences in Karnataka inMarch, Madhya Pradesh inApril and Rajastan in May. March 300C

Apri l 380C

May 480C

Hot Weather Season

Module 1

Seasons

Lecture 1

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Temperature-July

250C

300C

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Seasons

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Pressure-July

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Seasons

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LOO

KALBAISAKHI

BARDOLI

CHHEERHA

MANGO

SHOWER

BLOSSOM

SHOWER

Storms in Hot Weather Season

(climateofindia.pbworks.com) Module 1

Seasons

Lecture 1

S

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It extends from J une toSeptember.

Intense heating in northwest India creates low

pressure region.

Low pressure attract thewind from the surroundingregion.

After having rains for a fewdays sometime monsoonfails to occur for one ormore weeks is known asbreak in the monsoon.

South West Monsoon

LOW PRESSURE

HIGH TEMPERATURE

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Seasons

Lecture 1

S

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INTER TROPICAL CONVERGENCE ZONE

Arabiansea Branch

Bay ofBengal

Branch

Monsoon Wind

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Seasons

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Onset of SW Monsoon

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Seasons

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It extends from October toNovember

Vertical sun rays start shiftingtowards Northernhemisphere.

Low pressure region shiftfrom northern parts of Indiatowards south.

Owing to the conditions ofhigh temperature andhumidity, the weatherbecomes rather oppressive.

This is commonly known asthe October heat

LOW PRESSURE

Retreating Monsoon Season

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Seasons

Lecture 1

S

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Withdrawal of Monsoon

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Seasons

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Seasons

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> 200cm

100-200cm

50-100 cm

< 50cm

Distr ibut ion of Rainfall

(climateofindia.pbworks.com) Module 1

Seasons

Lecture 1

Seasons

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The variability of rainfall is computedwith the help of the following formula:C.V.= Standard Deviation/ Mean * 100

Variability 50% found in Western

Rajastan, J & K and interior parts ofDeccan.

Region with high rainfall has lessvariability.

Variability of Rainfall

Seasons