INTRODUCTION TO GROUNDWATER

Riddhi Singh Lecture 1b

Email: riddhi@civil.iitb.ac.inImage: https://www.flickr.com/photos/savethechildrenusa/5597515441

CE 626

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Today we will learn about…

• The need to study groundwater

hydrology

• Groundwater in the hydrologic cycle

• History of groundwater hydrology

• Groundwater resources of India

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MOTIVATION

WHY STUDY GROUNDWATER?

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http://www.rainwaterharvesting.org/Rural/Traditional3.htm#kul

The distribution of water resources is rather skewed…

Image: http://penangmonthly.com/wp-content/uploads/2012/06/pg-water-supply-diag01.gif

Numbers from Chow et al. (2010)

1.7%

0.76%

Soil moisture: 0.0012%

Atmosphere: 0.001%

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Groundwater is water under positive (greater than atmospheric)

pressure in the saturated zone of earth.

5Image: http://nile.riverawarenesskit.org/English/NRAK/RS_L3/assets/images/Figure_3.1.7_Groundwater_Cycle02.gif (left)

http://penangmonthly.com/wp-content/uploads/2012/06/pg-water-supply-diag01.gif (right)

~30% of all freshwater

~99% of liquid freshwaterGroundwater provides storage beneath the ground.

It is a critical component of the hydrologic cycle, sustaining flow

in rivers during periods of no rainfall

6Image: http://www.fws.gov/mountain-prairie/ea/images/CO%20Partners%201.Full%20Sizejpg%20%281%29.jpg

We understood this in the past, and constructed many

structures to recharge the groundwater

7Image: http://www.rainwaterharvesting.org/Rural/img/Eri-img.jpg

Eri

Approximately one-third of the irrigated area of Tamil Nadu is watered by

eris (tanks). Without eris, paddy cultivation would have been impossible.

In the18th century about 4-5 per cent of the gross produce of each village

was allocated to maintain eris!

http://www.rainwaterharvesting.org/Rural/Traditional3.htm#kul

Groundwater supplies 2 billion people with drinking water

and ~1/3rd of land mass with irrigation water

8https://blogs.egu.eu/network/water-underground/2016/12/20/limits-to-global-groundwater-use/

The year when groundwater falls below 100 m depth, often used as

an indication of economic infeasibility.

But today, it is the most unregulated part of the human

withdrawals in India. We don’t know how much we are using!

9Image: http://ibnlive.in.com/news/rural-water-supply-schemes-suffered-due-to-unregulated-extraction-of-ground-water-cag/501326-3.html

Due to unregulated use, this precious resource is running out in

many parts of the country. Efforts to preserve it are needed.

10Image: http://ej.iop.org/images/1748-9326/4/3/035005/Full/9925403.jpg

Knowledge of groundwater is needed to:

• Solve problems related to groundwater supply and control

– Is there enough water?

– Is the quality acceptable?

– How much will it cost to pump it?

• Groundwater control: projects requiring excavations below

groundwater table

• Aquifer protection:

– Contamination prevention by zoning of recharge areas

– Insuring adequate recharge to maintain groundwater

reserves

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GROUNDWATER IN THE

HYDROLOGIC CYCLE

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The hydrologic cycle refers to the movement of water

between ocean, land and atmosphere

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Numbers from Chow et al. (2010)

What is(are) the driving force(s) behind this movement?

Image: http://www.miwaterstewardship.org/Portals/0/images/hydrologic_cycle.323px.jpg

424

385

39

61100

38

1

Some terms:

• Evaporation

• Precipitation

• Interception

• Infiltration

• Overland flow

• Subsurface flow

• Streamflow

• Groundwater

• Recharge

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Image: http://www.miwaterstewardship.org/Portals/0/images/hydrologic_cycle.323px.jpg

Definition

Groundwater hydrology may be defined as the science of the

occurrence, distribution and movement of water below the

surface of the earth.

Todd , 1980

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Subsurface water flows beneath the land surface

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6Image: http://www.sfu.ca/geog355fall01/awhall/runoff_paths.jpg

Based on Figure 4.1.1 in Chow et al. (2010)

Subsurface outflow

Groundwater

outflow

Soil moisture

Saturated flow

unsaturated flow

Schematic showing subsurface water zones and flow processes.

Capillary forces saturate the porous medium for a short distance

in the capillary fringe

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7Image: http://www.sfu.ca/geog355fall01/awhall/runoff_paths.jpg (left)

http://www.amiadini.com/NewsletterArchive/141007-NL176/envEnl-176_clip_image008.jpg (right)

Based on Figure 4.1.1 in Chow et al. (2010)

Schematic showing subsurface water zones and flow processes.

Systems diagram of the hydrologic cycle

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Figure 1.2.1 in Chow et al. (2010) Block-diagram representation

of the global hydrologic system

EvaporationPrecipitation

Interception

Transpiration

Runoff to streams and ocean

Surface runoff

Subsurface flow

Groundwater flow

Groundwater recharge

Infiltration

Overland flow

Atm

osp

heri

c W

ater

Subsu

rfac

e W

ater

Surf

ace

Wat

er

An alternative view by Fetter

19Figure 1.4 in Fetter’s book

Atmosphere (water vapor)

Land surface (ice, snow, depression

storage)

Vadose zone (soil moisture)

Zone of saturation (groundwater)

Lakes, ponds, streams and rivers

(surface water)Ocean

(seawater)

Lithosphere (magmatic water)

EvapotranspirationPrecipitation Precipitation Precipitation Evaporation

Overland flow

Interflow

Baseflow

Subsea outflow

Infiltration Vapor movement

Capillary riseGravity drainage

Runoff Risin

g magm

a in vo

lcano

Sea floor ventSubduction

Evaporation

In class exercise: Residence time calculation

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Q. Given that that total volumes of groundwater available as

freshwater and saline water are 10,530,000 km3, and 12,870,000

km3, respectively. Estimate the residence time of groundwater if

groundwater discharge from land to oceans is 2200 km3/yr.

In class exercise: Residence time calculation

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Q. Given that that total volumes of groundwater available as

freshwater and saline water are 10,530,000 km3, and 12,870,000

km3, respectively. Estimate the residence time of groundwater if

groundwater discharge from land to oceans is 2200 km3/yr.

Groundwater basins

22,00 km3/yr? 10,530,000 km3 + 12,870,000 km3

( )10,530,000 12,870,00010,000

2200Residence time years

+=

HISTORY OF GROUNDWATER

HYDROLOGY

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Groundwater use predated understanding of its physics

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Image: By Amada44 - Own work, Public Domain,

https://commons.wikimedia.org/w/index.php?curid=3269373

A gently sloping tunnel is dug through alluvial

material leads water by gravity flow from beneath

the water table at its upper end to a ground surface

outlet and irrigation canal at lower end.

Vertical shafts dug at closely spaced intervals provide

access to the tunnel. (Todd)

More details: https://whc.unesco.org/en/list/1506/(Top image) Author: S.H. Rashedi; Copyright: © S.H. Rashedi;

Permanent URL: whc.unesco.org/en/documents/141554

(Bottom image) Author: ICQHS Archive; Copyright: © ICQHS;

Permanent URL: whc.unesco.org/en/documents/141563

Qanats: horizontal wells

Tank systems evolved in Peninsular India due to

its physio-climatic setting

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Image from: http://www.dhan.org/development-matters/wp-content/uploads/2012/10/article05_07.bmp

Kunds of Thar

25Image from: http://www.rainwaterharvesting.org/methods/traditional/kund2.jpg

These are primarily rainwater harvesting structures that store the rainfall of the

monsoon months to provide water in the rest of the year. They are typically 5 m deep

and 2.5 m in diameter and takes 25 days to build and cots about Rs. 12,000. A lid is

placed on the top after construction.

Control parameters: slope of catchment area, vegetation, cleanliness

The widely held belief was that the

subterranean source of springs and

rivers were the seas.

From Athanasius Kircher’s Mundus

Subterraneus, ca. 1664.

Source: Adams (1938, 437).

Another belief was that air

condenses water in cool caves,

which contributes to spring water

the ‘infiltration theory’ first

proposed by Roman architect

Vitruvius, reiterated by French

philosopher Palissy, was generally

ignored until Renaissance.

Source: http://sciencevsaging.org/fr/node/425 26

Pre-renaissance concepts of source of groundwater

Modern concept of the water cycle was first established in

‘Origin of fountains’ printed in Paris in 1674

Dooge (2001)

By measuring rainfall and flow in the river under consideration, the author established that

rainfall was more than sufficient to provide water to the river.

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Earlier developments in groundwater

hydrology…

Homer, Thales and Plato

Springs by seawater

Vitruvious

Infiltration

Palissy (1580)

Reiterates the

infiltration theory

Groundwater hydrology by Todd.

Rene Descartes (1596-1650)

Reiterates seawater idea

Perrault (1611-1680)

Proves that rainfall

has sufficient volume

to support stream

flows

Mariotte (1684)

Reiterates Perrault’s observations

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Halley (1693)

Seawater

evaporation

sufficient to account

for all springs and

streamflow

Modern developments…

Poiseuille (1839)

Capillary flow

Darcy (1856)

Porous media flow

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Green & Ampt (1911)

Infiltration

Richard (1931)

Unsaturated flow

Horton (1933-1945)

Infiltration theory,

drainage processes

Boussinesq (1904)

2D groundwater

flow in an aquifer

Dupuit (1863)

The famous ‘approximation’

related to slope of phreatic surface

Thiem (1906)

Radial flow to

wells

Dachler, Imbeaux, Keilhack, Koehne, Kozeny, Prinz,

Schoeller, G. Thiem, Hazen, King, Slichter, Chamberlin,

Darton, Lee, Mendenhall, Meizner, and many more

GROUNDWATER RESOURCES OF

INDIA

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Groundwater resources of India

31Suhag, R., 2016. Overview of Ground Water in India, available at India-

WRIS website.

In Class

The estimated usable surface water and groundwater

resource of India are 690 BCM/year and 433 BCM/year,

respectively. If this water was spread across the country,

what would be the depth of each resource?

Compare this with the average annual rainfall in India that

ranges from 300-650 mm/year, according to Wikipedia.

(Hint: use surface area as 3.3 million km2)

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Groundwater resources of India: exploitation statistics

33Suhag, R., 2016. Overview of Ground Water in India, available at India-

WRIS website.

High development in Delhi, Haryana, Punjab and Rajasthan (>100%), annual

groundwater consumptive > recharge

Critical regions: Himachal Pradesh, Tamil Nadu, Uttar Pradesh, Puducherry (>70%).

Overall development 58% in 2004 and 62% in 2011.

Groundwater resources of India: exploitation statistics

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Suhag, R., 2016. Overview of Ground Water in India, available at India-

WRIS website.

Major contributor to irrigation…

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Suhag, R., 2016. Overview of Ground Water in India, available at India-

WRIS website.