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Dr. Sanghamitra Kundu

Dept. of Civil Engineering

Introduction to Hydrology and Water Resources Engineering

What is Hydrology?

Hydro means water

Logos means science

Hydrology may be defined as the science that dealswith the depletion and replenishment of our waterresources. It deals with surface as well as groundwaters, as far as their occurrence, circulation,distribution, chemical and physical properties,reactions to environment and living beings, etc., areconcerned.

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Engineering Hydrology

� Engineering hydrology is the branch of hydrologywhich deals with estimation of water resource.

� It also investigates hydrologic problems such asfloods and droughts, and develops strategies tomitigate them.

Problems in Hydrologic Studies and Water Resource Estimation

� Uncertainty of precipitation and its seasonal occurrence

� Seasonal flow of rivers, and

� Population growth and rising standards of living

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Hydrology – An interdisciplinary science

� Draws many principles from

� Physics, chemistry, geology, fluid mechanics, mathematics, probability and statistics, operations research

� Hydrometeorology, climatology

� Potamology, limnology, glaciology, oceanology

� Agronomy, hydrogeology, geohydrology

Water Cycle or Hydrologic Cycle

� A continuous process by which water is purified by evaporation and transported from the earth's surface (including the oceans) to the atmosphere and back to the land and oceans.

� It represents various stages of the transformation of water from one form to another;

� However, the total amount of water above, on and below the surface of the earth remains constant.

� Such system is a closed system having no beginning and end, and hence it is called a hydrologic cycle.

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� People tap the water cycle for their own uses.

�Water is diverted temporarily from one part of the cycle by pumping it from the ground or drawing it from a river or lake.

� It is used for a variety of activities such as households, businesses and industries;

� For irrigation of farms and parklands;

� And for production of electric power.

� After use, water is returned to another part of the cycle: perhaps discharged downstream or allowed to soak into the ground. Used water normally is lower in quality, even after treatment, which often poses a problem for downstream users.

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Elements of Hydrological Cycle

� Evaporation� Transpiration� Condensation� Precipitation� Runoff (Surface runoff)� Interception� Infiltration� Surface Detention� Depression Storage� Interflow � Groundwater flow

Ancient Hydrologic History10

� Hydrology has been a subject of investigation and engineering for millennia. � About 4000 B.C. the Nile was dammed to improve agricultural productivity of previously barren lands. [FIRST DAM]

� Mesopotamian towns were protected from flooding with high earthen walls. Aqueducts were built by the Greeks and Ancient Romans

� History of China shows they built irrigation and flood control works.

� The ancient Sinhalese used hydrology to build complex irrigation Works in Sri Lanka, also known for invention of the Valve Pit which allowed construction of large reservoirs, anicuts and canals which still function.

Loucks and van Beek, 2006

Nile RiverThe longest river in the world(6650 km)

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Ancient Hydrologic History11

� There were many Nilometers in Egypt, but the most important ones were at Elephantine Island.

� The Nilometer was important as it measured the rise of the floodwaters of the Nile. If the Nile did not rise enough, the land would experience famine conditions. If the Nile rose too high, it would flood and destroy the villages. Every temple in Egypt had a Nilometer because it was a symbol of life.

http://www.bibleplaces.com/aswan.htm

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[After Eagleson et al., 1991, p.20]

Ancient Hydrologic History

WATER

SECURITYAbundance

Security

Happiness

Suffering

Hunger

Disaster

NILOMETER READING IN ELLS

1 ELL = 1.1m

But hydrology is a young science….

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� Ven Te Chow has classified the historical development of hydrology into 8 periods� Period of speculation (Ancient times to 1400 AD)� Period of observation (1400 AD to 1600 AD)� Period of measurement (1600 AD to 1700 AD)� Period of experimentation (1700 AD to 1800 AD)� Period of modernization (1800 AD to 1900 AD)� Period of empericism (1900 AD to 1930 AD)� Period of rationalisation (1930 AD to 1950 AD)� Period of theorisation (1950 AD to 1965 AD)� Period of mathematical modelling and computerisation(1965 AD – till date)

Ancient Hydrologic History

After Berner and Berner, 1987

Oceans

97%

Water on land

3%

74%

11%

14%

1%

Ice caps and glaciers

Shallow groundwater(<750 m)

Deep groundwater(750-4000 m)

Lakes, soil moisture,atmosphere, rivers

Inventory of water on Earth

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Sources: Asian Development Bank; BBC; Earth Observatory; UNEP; UNESCO

Why Hydrology is Important

� Of total world water, 97.5% is salty water and only 2.5% is freshwater of which useablefreshwater accounts for about 0.5%

� Of the 0.5% useable freshwater, irrigation accounts for 70%, industry 20% and household10%

� Demand for and use of freshwater has tripled over the past half century, as worldpopulation has grown from 2.5 to 6.45 billion people

� By 2025 global water needs will increase with 40% more required for cities and 20% forgrowing crops

� The satellite photos show major freshwater depletion taking place on all continents, notablyin the Dead Sea, the Aral Sea, Lake Chad, the Mesopotamian Marshlands, the Evergladesand other water sources

� According to UNESCO estimates, by 2030 global demands for fresh water will exceed thesupply with potentially disastrous consequences

Sources: Asian Development Bank; BBC; Earth Observatory; UNEP; UNESCO

Why Hydrology is Important

� Water withdrawals are causing major rivers—such as the Colorado, the Nile, the YellowRivers—to run dry in sections, lakes to vanish and groundwater tables and aquifers to dropin many places

� Over the next 20 years, average water supply per person is estimated to drop by a third,potentially endangering human health, agriculture and the environment

� Water volume in the Aral sea has dropped by about 80% since 1960s, due to extensiveirrigation primarily for cotton production

� Current water levels in Lake Victoria are below normal and the lowest level sinceSeptember 1961

� In 2002, around 3.16 billion people (82%) in the Asia Pacific region had access toimproved water supplies, up from 74% in 1990

� Water pollution is a serious threat to the world’s water supply

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The Lake Aral disaster

Significance of HC?

� Design of Hydraulic Structures like� Dams, Bridges, Head-works, Spillways and Culverts etc.

� Municipal and industrial water supply� Irrigation Projects� Hydroelectric Power Generation� Flood Control Projects

� Reservoirs, levees, channel improvements and channeldiversions

� Environmental Pollution Control� Navigation� Erosion and sediment control

� E.g. River Kosi (http://ihrrblog.org/2011/07/12/re-addressing-the-problem-of-flooding-on-the-kosi-river/)

� Water resource sustainability

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Water resource sustainability

� It is the ability to use water in sufficient quantities and quality from the local to the global scale to meet the needs of humans and ecosystems for the present and the future to sustain life, and to protect humans from the damages brought about by natural and human-caused disasters that affect sustaining life.

� Availability of freshwater supplies

� Infrastructure

� Institutions for water supply and water excess management

Challenges to water resources sustainability

� Urbanization� Transformation on undeveloped land into urban land (including transportation corridors)� Reduced groundwater recharge due to paved surface areas and storm sewers

� Increase in volume of runoff with higher pollutant concentrations that reduces receiving water dilution effects

� Increased energy release (i.e. greenhouse gases, waste heat, heated surface runoff)

� Increased demand on water supply (municipal and industrial)� Increased groundwater discharge by pumping wells

� Decreased groundwater recharge due to export of wastewater collection by sanitary sewers

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Challenges to water resources sustainability

� Droughts and floods

Without demands, there is no drought, whether a given

supply of water is big small, or even zero

� Storage buffers

� Soil root zones

� Aquifers

� Lakes

� Reservoirs

� Surface stream flows

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� Climate change

� Consumption of water

“It is difficult to imagine that to produce one cup of coffee requires 140 litres of water and to produce 1 kg of beef requires 16,000 litres of water”

� Virtual water � Volume of water required to produce a commodity or service

�Water footprints�Water required to sustain a population

� Internal water footprint

� External water footprint

Challenges to water resources sustainability

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Contribution of different crops to the global water footprint (from Hoekstra and Chapagain, 2007)

Contribution of major consumers to the global water footprint (from Hoekstra and Chapagain, 2007)

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Irrigation

� Process of supplying water to land by artificial mean for the purpose of cultivation.

� To supplement the natural supply of water to land so as to obtain an optimum yield from the crop grown out of land

Necessity of irrigation

� Inadequate rainfall

� Uneven distribution of rainfall

� Growing a number of crops during a year

� Growing superior crops

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Scope of irrigation engineering

� Engineering aspect

� Development of the source of water for irrigation

� Surface water (rivers, lakes, ponds, tanks)

�Groundwater

� Arrangement for the conveyance of water from the source right upto the agricultural fields

Scope of irrigation engineering

� Agricultural aspect� Timely and systematic application of irrigation water to the agricultural fields by choosing suitable irrigation methods

� Proper leveling and shaping of the agricultural fields

� Soil investigation and classification of the agricultural land

� Consolidation of small and scattered holdings of the farmers

� Provisions of field channels

� Choosing the proper cropping pattern to suit the local soil and climatic conditions

� Introduction of improved hybrid and high-yielding varieties of crops

� Assessment of water requirement of the crops and distribution of water according to the needs of the crops grown

� Conservation of soil against erosion

� Provision of drainage system to control the water logging of the agricultural land

� Reclamation of saline and alkaline land to make it suitable for cultivation

� Plan the development of ancillary inputs such as fertilizers

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� Management aspect� Successful implementation and efficient management of both the engineering as well as agricultural aspects of the project

� Emphasis on scientific manner of cultivation with due control on all inputs so as to obtain the maximum yield

� Proper training and education of farmers through regular organization of courses

� Proper management of distribution of water to farmers by using some kind of rotation system as wara bandi

� Consolidation of land holdings of small farmers to increase irrigation efficiency

� Proper arrangement for the measurement of water used by farmers should be made to facilitate the collection of water charges from the farmers

� Suitable measures to be adopted to minimize the ill effects of irrigation

Scope of irrigation engineering

Benefits of irrigation

� Increase in Crop Yield

� Protection from Famine

� Cultivation of superior crops

� Elimination of mixed cropping

� General prosperity of the farmers

� Increase in the wealth of the country

� Generation of hydro-electric power� Ganga and Sharda canals in UP

� Domestic and Industrial water supply

� Inland Navigation

� Additional facilities for communication

� Canal plantations

� Increase in ground water storage

� Overall Development of the Country

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Ill-Effects of Irrigation

� Waterlogging

� Breeding places for mosquitoes

� Unhealthy climate

� Pollution of river flows and groundwater

History of irrigation development in India

� Earliest form� Inundation or flood irrigation

� Flood plains of Ganga, Indus and various other rivers of south and central India

� Wells and tanks were built in the drier regions

� Hindu and Muslim rulers constructed irrigation works

� First efforts of irrigation development� 1800-1836

� Directed towards the improvement and utilization of old indigenous works

� Western Yamuna Canal, Eastern Yamuna Canal and Cauvery Delta system renovated and opened for use

� 1836-1866� Upper Ganga Canal, Upper Bari Doab Canal, The Krishna and the Godavari Delta system constructed

� Agra Canal, Betwa Canal, Periyar Canal, Khadakwasla Storage Dam, Sone Canal system

� Beginning of 20th Century� Appointment of the First India Irrigation Commission

� Godavari Canal, Sarda Canal, Krishnaraja Sagar, Nizam Sagar

� Post-Independence� Bhakra Nangal, Gandak, Hirakud, Chambal, Nagarjunasagar, Damodar Valley, Koshi, Mahi, Indira Gandhi Nahar, Ramganga etc..

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Types of irrigation systems

� Classification based on the availability of irrigation water

� Flow irrigation

� Direct irrigation system

� Reservoir or Tank or Storage irrigation system

� Lift irrigation

� Classification based on the duration of irrigation

� Inundation irrigation

� Perennial irrigation