Chap 1_Introduction.pdf

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Rezaul Karim

Environmental Science and Technology

Jessore Science and Technology University

Hydrology: Chapter 1 Introduction


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Introduction

hydrology defined; a brief history;

the hydrologic cycle;

hydrologic equation / the hydrologic budget;

common units of measurement;

hydrological data;

scope of hydrology;

application of hydrology to environmental problems;

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Recommended references

Tim Davie (2002) Fundamentals of hydrology, RoutledgeFundamentals of Physical Geography, 2nd ed. Routledge

270 Madison Avenue, New York, NY 10016

Viessman, W., Jr., and G.L. Lewis, 2003. Introduction to

Hydrology, 5th

Edition. Harper Collins College Publishers,New York, NY.

Raghunath, H. M. (2006) Hydrology: principles, analysis and

design. 2nd ed. New age international (p) limited, publishers

4835/24, ansari road, daryaganj, new delhi - 110002 Chaw, David and Larry, Applied Hydrology

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Hydrology

The word hydrology combines the Greek word Hudorwhich means water and the logy designates a study

of.

It is also origins in the new Latin word hydrologia.

Most specifically, the general word hydrology refers to thescientific study of water and its properties, distribution,

and effects on Earths surface, soil and atmosphere.

The study of water can mean different things to different

professions. E.g. Chemist, ground water hydrologist,hydrologic engineer, planners, environmentalists, water

managers, and meteorologists and so on.

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Defination

Hydrology is an earth science. It encompasses the occurrence, distribution, movement

and properties of the waters of the earth.

Water and environmental issues are inextricably linked'

and it is important to clear understand how water isaffected by and how water affects ecosystem

manipulations.

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Importance of Water

Water is the most common substance on the surface ofthe earth, with the oceans covering over 70 per cent ofthe planet. Water is one of the few substances that can befound in all three states (i.e. gas, liquid and solid) withinthe earths climatic range.

The chemical properties of water are equally importantfor our everyday existence. Water is one of the bestsolvents naturally occurring on the planet. This makeswater vital for cleanliness.

The capability of water to support life goes beyondbodies of water; the human body is composed of around60 per cent water.

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Other importance

In places such as Norway, parts of the USA and New Zealandenergy generation for domestic and industrial consumption isthrough hydro-electric schemes, arnessing the combination ofwater and gravity in a (by and large) sustainable manner.

Water plays a large part in the spiritual lives of millions ofpeople. In Christianity baptism with water is a powerful symbol of cleansing

and God offers streams of living water to those who believe (John7:38).

In Islam there is washing with water before entering a mosque forprayer.

In Hinduism bathing in the sacred Ganges provides a religiouscleansing.

Many other religions give water an important role in sacred textsand rituals.

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Water regulates the Earths temperature. It also regulatesthe temperature of the human body, carries nutrients and

oxygen to cells, cushions joints, protects organs and

tissues, and removes wastes.

75% of a living tree is water. Human brains are 75% water.

Human bones are 25% water.

Human blood is 83% water.

A person can live about a month without food, but onlyabout a week without water.

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Worlds water resources

Item Area Land(106 km3)

Volume(km3)

Percent oftotal water

Percent of freshwaterOceans 361.3 1,338,000,000 96.5

GroundwaterFresh 134.8 10,530,000 0.76 30.1Saline I 34.8 12,870,000 0.93

Soil Moisture 82.0 16.500 0.0012 0.05Polar ice 16.0 24,023,500 1,7 68.6Other ice and

snow0.3 340,600 0.025 1.0

LakesFresh 1.2 91,000 0.007 0.26Saline 0.8 85,400 0.006

Marshes 2.7 11,470 0.0008 0.03Rivers 148.8 2,120 0.0002 0.006Biological water 510.0 1,1 2 0 0.0001 0.003Atmospheric

water510.0 12,900 0.001 0.04

Total water 5 10.0 1,385,984,610 100Fresh water 148.8 35,029,210 2.5 100

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Major aspects of hydrology

The main jobs of a hydrologist are collection and analysis of data,and making predictions out of this analysis.

Collection of data

The hydrologic data comprises rainfall data, snowfall and snowmeltdata, runoff data, topographic maps and groundwater data

Analysis of dataAnalysis of data includes checking it for consistency and homogeneity

as well as its various statistical parameters.

Prediction

Prediction means findings design values and maximum possible floods

and drought. Various approaches for prediction of hydrologic values Statistical approach

Physical approach and

Deterministic approach

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Hydrometeorological characteristics of

basin:

(i) long term precipitation, space average over the basin usingisohyets and Several other methods

(ii) Depth-area-duration (DAD) curves for critical storms (stationequipped with Self-recording rain gauges).

(iii) Isohyetal mapsIsohyets may be drawn for long-term average,annual and Monthly precipitation for individual years and months

(iv) Cropping patterncrops and their seasons

(v) Daily, monthly and annual evaporation from water surfaces in thebasin

(vi) Water balance studies of the basin

(vii) Chronic problems in the basin due to a flood-menacing river(like Tapti or Tapi in central India) or silt menacing river (likeTungabhadra in Karnataka)

(vii) Soil conservation and methods of flood control

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Scope of hydrology

The study of hydrology helps us to know

the maximum probable flood that may occur at a given siteand its frequency; this is required for the safe design of drainsand culverts, dams and reservoirs, channels and other floodcontrol structures.

The water yield from a basinits occurrence, quantity andfrequency, etc; this is necessary for the design of dams,municipal water supply, water power, river navigation, etc.

the ground water development for which a knowledge of thehydrogeology of the area, i.e., of the formation soil, rechargefacilities like streams and reservoirs, rainfall pattern, climate,

cropping pattern, etc. are required. The maximum intensity of storm and its frequency for the

design of a drainage project in the area.

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Application of hydrology to

environmental problems It is true that humans cannot exist without water; it is also true that water,

mismanaged, or during times of deficiency (droughts), or times of surplus (floods),can be life threatening.

Furthermore, there is no aspect of environmental concern that does not relate insome way to water. Land, air, and water are all interrelated as are water and all lifeforms.

Accordingly, the spectrum of issues requiring an understanding of hydrologicprocesses is almost unlimited.

As water becomes scarcer and as competition for its use expands, the need forimproved water management will grow.

And to provide water for the world's expanding population, new industrialdevelopments food production, recreational demands, and for the preservation andprotection of natural systems and other purposes, it will become increasinglyimportant for us to achieve a thorough understanding of the underlying hydrologic

processes with which we must contend. This is the challenge to hydrologists water resources engineers; planners,

policymakers, lawyers, Economists, and others who must strive to see that futureallocations of water are Sufficient to meet the needs of human and natural systems.

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Documents

Chap 1_Introduction.pdf