Lecture 1GWH

8/12/2019 Lecture 1GWH

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Ground-water hydrology is the subdivision of the science of hydrology that deals

with the occurrence, movement, and quality of water beneath the Earth's surface .It is interdisciplinary in scope in that it involves the application of the physical,

biological, and mathematical sciences .

It is also a science whose successful application is of critical importance to the

welfare of mankind.

Because ground-water hydrology deals with the occurrence and movement ofwater in an almost infinitely complex subsurface environment, it is, in its most

advanced state, one of the most complex of the sciences .

On the other hand, many of its basic principles and methods can be understood

readily by non hydrologists and used by them in the solution of ground-water

problems .

The purpose of this report is to present these basic aspects of ground-water

hydrology in a form that will encourage more widespread understanding and use .

Introduction


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Some More Features

Ground-water hydrology, as noted earlier, deals not onlywith the occurrence of underground water but also with itsmovement .

Contrary to our impressions of rapid movement as we

observe the flow of streams in caves, the movement ofmost ground water is exceedingly slow.

The truth of this observation becomes readily apparentfrom the table, which shows, in the last column, the rate ofwater exchange or the time required to replace the water

now contained in the listed parts of the hydrosphere . It is especially important to note that the rate of exchange

of 280 years for fresh ground water is about 1/9,000 therate of exchange of water in rivers .


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Ground Water Hydrology


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Some Facts

Estimates from river outflows indicate 17 x 109

Tons/Year of material is transported into the

Ocean. Another 2 or 3 x 109 Tons/Year is

trapped in reservoirs.

80% of material transported is particulate 20%

is dissolved

0.05 mm/yr (may have been accelerated by

man, and actual rates may be much larger)


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So where does all this water Go


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Some facts about India

Geographical Area 329 Million hectare

(2.45% of world land area)

Cultivable Area 184 Mha (~ 56 %)

Forest Cover 21%

Ultimate irrigation Potential 139.9 Mha

Population 1.027 billion(16% of world population)


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Indias Water Resources

Annual average precipitation - 4000 BCM- Highly variable in space and time- Minimum - 100 mm in Western Desert

- Maximum - 11000 mm in North EasternRegion

Rainfall during June to September 3000 BCM

Average annual potential 1869 BCM

Utilisable Water Potential 1123 BCM - Surface water690 BCM- Ground water433 BCM


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IndiaPresent Status of Development

Live storage capacity increased from 15.6BCM in 1950 to 225 BCM now.Another-

64 BCM under construction

108 BCM contemplated

Foodgrain production increased from 51million tonnes in 1950 to 217 million tonnesin 2007 p.a.

Irrigation potential created by 2006 is 102.77Mha against 22.6 Mha in 1951


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Share of agriculture in GDP declined frommore than half in 1950 to less than 20%

currently but largest employment and

livelihood Irrigated agriculture has massive contribution

towards food production

Irrigation enables higher production from landspecially with use of high yielding varieties,

fertilizers and other inputs


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Agricultural production increase through:

- expansion of cultivated areas,

-shift in cropping pattern,

- enhanced productivity by irrigation

Irrigation development influences greatly

incidence of poverty and alleviation


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Development of Ground Water

Groundwater irrigating about 60% of irrigated area

also important for agricultural production.

Concerns about groundwater are-

* over-exploitation in some areas

* under-utilization in large parts of country


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Development of Ground Water

In India, ownership of groundwater

with owner of land resulting inoverexploitation in certain regions.

Priority given to exploit groundwaterwhere abundantly available


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Watershed Hydrologic Budgets

A watershed Comprises of

(drainage basin, river basin, catchment)

Area that topographically appears tocontribute all the water that flows through a

given cross section of a stream. In other

words, the area over which water flowing

along the surface will eventually reach the

stream, upstream of the cross-section.


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Horizontal projection of this area is the

drainage area. The boundaries of a watershed are called a

divide, and can be traced on a topographic

map by starting at the location of the streamcross-section then drawing a line away from

the stream that intersects all contour lines at

right angles. If you do this right, the lines

drawn from both sides of the stream should

intersect. Moving to either side


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Discharge into Lake Parabola

If there is constant volume flux Q m3/day into

the lake, how does the depth depend on time? (At time 0, the depth is Ho m).

Since there is no outflow, the charge in storage

must equal the inflow Mass-balance (waterbalance) equation


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Lake Parabola(A simple quadratic model of the cross section of a circular lake)


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Lecture 1GWH

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