Chennai's water woes and

the way forward

L. ElangoProfessor

Department of Geology Anna University, Chennai

www.elango.net.in

Brain Storming Meet on Chennai Water Management, 3 August 2019

Geology of Chennai and surroundings

2

Geology of

Chennai

Groundwater occur

in

weathered/fractured

rocks and

unconsolidated

formations

3www.rainwaterharvesting.org

Water supply - Location of

reservoirs & well fields

L.Elango

Water requirement

• 8.2 millionPopulation

• 8.2 x 135 liters = 1107 MLDWater

requirement

• About 800 MLD? Now 500Water

supplied

Private sources

• The remaining?

• Private wells

Major sources

• Reservoirs – 400MLD

• Krishna – 50 MLD

• Veeranam/NLC – 200 MLD

• North/South Chennai Groundwater – 100

MLD

• Desalination – 180 MLD

• Private wells

6

Today

• Quarries about 50 MLD

7

https://www.thehindu.com/news/cities/chennai/water-supply-in-city-cut-to-525-

from-830-mld-hc-told/article28023481.ece

http://www.newindianexpress.com/cities/ch

ennai/2019/jun/25/prached-chennai-to-get-

water-from-11-more-kancheepuram-

quarries--1994856.html

•Rainfall dependent

•Extreme rainfall events – flooding

•Seawater intrusion and groundwater quality

•Urbanisation and loss of water bodies

•Reduction in groundwater recharge

•Demand supply gap – recycling of water

What are the concerns?

8

Chennai Floods – December 2015

9

Pics: Senthilkumar

Sampling wells

Sampling wells

10

Groundwater chemical quality

after floods

11

Nature Sci Data (2017)

Affected Vs Not affected wells

Nature Sci Data (2017)

12

Seawater intrusion

Envi. Ear. Sci (2013) 13

Extent of seawater intrusion

1969

2015

14

Impact of a check dam

15Parimalarenganayaki et al (2015)

16

MAR through Ponds

Before After

Raicy & Elango (2017)

Expected regions benefited by check dams

Approximate area of

impact from MAR

17

Integrated Modelling Approach

18

1. Construction of additional check dams

(existing 9, suggested 6 more)

2. 1 + 1 m increase in crest level of all

existing check dams

3. 2 + rehabilitation of defunct water bodies

4. 3 + Interlinking of A and K rivers

5. 4 + 10% increase in recharge and SL rise

Model prediction under

different scenarios

19

Extent of seawater intrusion

1969

1990

2000

2004

2010

2015

2030-recharge

structures20

Water demand for the Chennai

city with growth in population

21Paul & Elango (2018)

Water Evaluation And Planning System

www.weap21.org

Coverage of demand with the

proposed third desalination

22

Madras

Demand Site Coverage (% of requirement met)

Scenario: Reference, All months (12)

Jan

1991

Dec

1991

Nov

1992

Nov

1993

Oct

1994

Oct

1995

Sep

1996

Sep

1997

Sep

1998

Aug

1999

Aug

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Jul

2001

Jul

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2003

Jun

2004

Jun

2005

May

2006

May

2007

Apr

2008

Apr

2009

Apr

2010

Mar

2011

Mar

2012

Feb

2013

Feb

2014

Jan

2015

Jan

2016

Jan

2017

Dec

2017

Dec

2018

Nov

2019

Nov

2020

Oct

2021

Oct

2022

Oct

2023

Sep

2024

Sep

2025

Aug

2026

Aug

2027

Aug

2028

Jul

2029

Jul

2030

Perc

ent

100

95

90

85

80

75

70

65

60

55

50

45

40

35

30

25

20

15

10

5

0

Paul & Elango (2018)

Coverage with the proposed

new reservoir

23

Madras

Demand Site Coverage (% of requirement met)

Scenario: Reference, All months (12)

Jan

1991

Dec

1991

Nov

1992

Nov

1993

Oct

1994

Oct

1995

Sep

1996

Sep

1997

Sep

1998

Aug

1999

Aug

2000

Jul

2001

Jul

2002

Jun

2003

Jun

2004

Jun

2005

May

2006

May

2007

Apr

2008

Apr

2009

Apr

2010

Mar

2011

Mar

2012

Feb

2013

Feb

2014

Jan

2015

Jan

2016

Jan

2017

Dec

2017

Dec

2018

Nov

2019

Nov

2020

Oct

2021

Oct

2022

Oct

2023

Sep

2024

Sep

2025

Aug

2026

Aug

2027

Aug

2028

Jul

2029

Jul

2030

Perc

ent

100

95

90

85

80

75

70

65

60

55

50

45

40

35

30

25

20

15

10

5

0

Paul & Elango (2018)

Coverage with reuse of treated

waste water

24

Madras

Demand Site Coverage (% of requirement met)

Scenario: Reference, All months (12)

Jan

1991

Dec

1991

Nov

1992

Nov

1993

Oct

1994

Oct

1995

Sep

1996

Sep

1997

Sep

1998

Aug

1999

Aug

2000

Jul

2001

Jul

2002

Jun

2003

Jun

2004

Jun

2005

May

2006

May

2007

Apr

2008

Apr

2009

Apr

2010

Mar

2011

Mar

2012

Feb

2013

Feb

2014

Jan

2015

Jan

2016

Jan

2017

Dec

2017

Dec

2018

Nov

2019

Nov

2020

Oct

2021

Oct

2022

Oct

2023

Sep

2024

Sep

2025

Aug

2026

Aug

2027

Aug

2028

Jul

2029

Jul

2030

Perc

ent

100

95

90

85

80

75

70

65

60

55

50

45

40

35

30

25

20

15

10

5

0

Paul & Elango (2018)

Even with the various

augmentation steps?

Demand supply gap by 2050!

25

Madras

Demand Site Coverage (% of requirement met)

Scenario: Reference, All months (12)

Jan

1991

May

1992

Oct

1993

Mar

1995

Aug

1996

Jan

1998

Jun

1999

Nov

2000

Apr

2002

Sep

2003

Feb

2005

Jul

2006

Dec

2007

May

2009

Oct

2010

Mar

2012

Aug

2013

Jan

2015

Jun

2016

Nov

2017

Apr

2019

Sep

2020

Feb

2022

Jul

2023

Dec

2024

May

2026

Oct

2027

Mar

2029

Aug

2030

Jan

2032

Jun

2033

Nov

2034

Apr

2036

Sep

2037

Feb

2039

Jul

2040

Dec

2041

May

2043

Oct

2044

Mar

2046

Aug

2047

Jan

2049

Jun

2050

Perc

ent

100

95

90

85

80

75

70

65

60

55

50

45

40

35

30

25

20

15

10

5

0

Paul & Elango (2018)

Way forward

• Urban planning - need to protect

groundwater recharge areas

• Water bodies to be rejuvenated

• Supply reservoirs to be deepened

• Periodical maintenance - to be ensured

• Direct storage of rainwater in sumps

• RWH structures – annual maintenance

• Recycling of waste water

Our research in media

L.Elango

www.saphpani.eu

elango@annauniv.edu

www.elango.net.in

Thank you for your attention

Acknowledgement

28