The document discusses the impacts of large dams on the environment and climate, using the Tehri Dam in Uttarakhand, India as a case study. It summarizes that the Tehri Dam provides benefits like hydroelectric power, flood control, irrigation, and tourism, but also resulted in mass displacement of people, deforestation, and impacts on biodiversity. Mitigation efforts were undertaken for afforestation, erosion control, and protecting displaced communities and the environment.

1. WELCOME

2. IMPACT OF LARGE DAMS ON
ENVIRONMENT AND CLIMATE

3. INTRODUCTION
A dam is essentially an artificial wall constructed across a river which converts a
running water ecosystem into a lake type ecosystem.
Dams are also known to cause environmental impacts which ranges from effects on
flora and fauna and natural flow of water. Dams are also known to be prone to
earthquakes and other natural disasters.

4. • PURPOSE OF STUDY: To bring out the positive and
negative impacts of large dams in their real perspectives.
• CASE STUDY: Tehri Dam, Uttarakhand, India
• METHODOLOGY: Analysis of financial, technical,
environmental and social data and weigh the same
impartially
OUTLINE

5. CASE STUDY: TEHRI DAM
• LOCATION: On Bhagirathi river, near Tehri in Uttarakhand,
India (30°22´40˝N, 78°28´50˝E)
• CONSTRUCTION BEGIN: 1978
• OPENING: 2006
• COST: US$ 1 Billion (approx.)
• OWNER: THDC India Ltd.

6. SITE SELECTION
1. Presence of s-shaped narrow gorge followed in upstream by a
considerable broad valley
2. Extensive terrace of the valley
3. Uniform geo-mechanical characteristics of disposed strata
4. Absence of any major tectonically active feature
5. Location at downstream of confluence of Bhagirathi and Bhilangana
rivers

7. TECHNICALASPECTS
1.Dams and Spillways
2.Reservoir
3.Power Station
4.Structural Design

8. DAM AND SPILLWAYS
Type of dam: Embankment, earth
and rock-fill
Impounds: Bhagirathi river
Height: 260.5m (855 feet)
Length: 575m (1886 feet)
Width(crest): 20m(66 ft)
Width(base): 1128m (3701 ft)
Spillway type: Gate controlled
Spillway capacity: 15,540 m3/s
(549,000 cu. ft/s)

9. RESERVOIR
Total capacity: 4.0 km3 (3,200,000 acre-feet)
Surface: 52 km2 (20 sq. m)
POWER STATION
Turbines: Vertical Francis turbines
Installed capacity: 1000 MW (1,300,000 hp)
Maximum planned: 2,400 MW

10. STRUCTURAL DESIGN
1. U/S slope=2.5:1 and D/S slope=2.0:1
2. Crest=20m, which increases to 25m at its contact with abutments
3. Free board=9.5m above FRL
4. The D/S filter is capable of preventing migration of finest particles
(clay flocks) in the event of its cracking
5. Compaction of dam shell material=2.36 tons/m3
6. The dam embankment is founded directly on bedrock, after removal of
all loose, semi compact overburden
7. Provision of access galleries at three different levels

11. MAIN DAM CROSS-SECTION

12. SOCIALASPECT
1. MASS DISPLACEMENT: 109 villages (full or partial) and the
Tehri town population were displaced.
Mitigation: Rehabilitation and Resettlement Program, for rural and
urban population
2. PUBLIC HEALTH: Comprehensive study of water-borne
diseases made and dust pollution level at construction site monitored.

13. ENVIRONMENTAL ASPECTS

14. ENVIRONMENTAL IMPACTS
1. Deforestation
2. Risk of soil erosion
3. Risk of water-logging and salinity
4. Impact on biodiversity
5. Water quality

15. MITIGATIONS
1. Compensatory afforestation to counter deforestation
2. Undertaking of Catchment Area Treatment and creating green-belt to
prevent soil erosion
3. Common Area Development Plan to prevent water-logging
4. Counter-measures undertaken to protect biodiversity
5. Water Quality Monitoring to control BOD and dissolved oxygen levels

16. ECONOMIC ASPECT
1. Hydro Power
2. Road network
3. Prevention of flood
4. Industry
5. Tourism
6. Irrigation
7. Drinking water supply

17. HYDRO-POWER

19. HYDRO-POWER: TODAY & TOMORROW

20. 0
500
1000
1500
2000
2500
3000
3500
4000
4500
2006-07 2007-08 2008-09 2009-10 2010-11 2011-12 2012-13 2013-14
TARGET (MU)
ACHIEVEMENT (MU)
GENERATION FROM TEHRI HPP

21.  MUNICIPAL WATER SUPPLY: Water from the Tehri Dam is supplied to
the Municipalities in Delhi NCR, Uttar Pradesh and Uttaranchal
 IRRIGATION: Uttar Pradesh and Uttaranchal shares water from the dam for
irrigation.
 FLOOD CONTROL: The presence of the Tehri Dam reduced the effect of
the catastrophic flood of June 2013 and protected Hrishikesh from disaster.
 TOURISM: The Tehri Dam has become a major source of employment
generation as tourist attraction in Uttaranchal.

22. CONCLUSION
“ Dams are the temples of modern India.”
-Pandit Jawaharlal Nehru
First Prime Minister of Independent India

23. THANK YOU
PRESENTATION BY:
PRASAD MUKHERJEE, B. TECH (CIVIL ENGINEERING)
UNIVERSITY OF ENGINEERING AND MANAGEMENT, JAIPUR
(Rajasthan)