Script for the large dam PPT
Slide 1
The first slide is used to explain the concept of a dam. Emaphasisisng :
1- creates a reseroir by changing the course of flowing water in turn submerging
land
2- downstream river is affected as water is held back in the reservoir
Slide 2
Before introducing slide 3 it may be a good idea to throw the question open to the class
and get responses from them. The question posed will be
“Why do you think dams are built?”
The answers should be put on the black board and then slide 2 should be used to show all
the uses of a dam.
Slide 3
Poses the question
“Do dams do a lot of good?”
The idea is to hear back from the class.
Slide 4
Introduces the idea that all dams don’t do good.
Slide 5
Before the discussion moves further there is a need to clarify what a large dam is. That
the further discussion will focus on large dams and not the small dams which do not
create many of the prblems to be discussed in the session. Following is an extract from
the World Comission on Dams (WCD)* explaining what a large dam is:
From the WCD Report :
What is a large dam?
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According to the International Commission on Large Dams (ICOLD), a large dam is 15 m
or more high (from the foundation).
If dams are between 5-15 metres and have a reservoir volume of more than 3 million
cubic metres they are also classified as large dams.
Using this definition, there are more than 45 000 large dams around the world.
Slide 6
India fact sheet : The idea of running thru the fact sheet is to make the sudents realise the
significance of the large dam issue in India.
• 4,300 dams
• India is one of the world’s major dam building countries
• land area submerged by large dams = about 37,500 square kilometers
• People displaced = about 42 million
Slides 7- 13
Look into the impact large dams have in terms of
1- Cost over runs
2- Social Impact :Displacement and Rehabilitation issue
3- Environmental Impact
Explaining slides 7-11 : Construction of the dam leads to submergence and diplacement
of people with insufficient compensation and rehabilitation.
Displacement : 40-80- million people have been displacen by the 45000 large dams built
all over the world. India has 9% of the world’s largest dams and so we have a substantial
displaced population. Displacement causes unique problems for those who are displaced,
let us consider these problems :
1- They loose their land which is their primary source of livelihood. More often than
not they are not given land for land as there isn’t enough land. Millions of
hectares of fertile farmland is drowned by the dam and is lost forever, we can not
manufacture new land. Without a source of livelihood the displaced are left with
no food security. Many are reduced to doing manual labour work in urban area eg
the Bargi dam oustees moed into Jabalpur slums to take up all kinds of odd jobs
like construction work, rickshaw pulling.
2- Community relationships are broken : breaks community bonds as the displaced
are scattered and struggling to survive
3- Displaced often meet with state repression and human rights violation – as the
project affected are often poor and indigenous peole in most cases.
4- Those affected are not part of the decision making process as to whether the dam
should or should not be built.
Slide 12
But the displaced are not limited to those whose land are drowned by the reservoir but
there are also accruing forms of secondary displcement. These are :
1- those living downstream and depend on the river for their livelihood either
through fisheries or using the fertile river banks for farming. These people loose
their livelihood as the damming of the river changes the flow in the downstream
area.
2- Those displaced by the irrigation canals
Most of these people are not considered project affected and therefore neither given any
rehabilitation nor considered displced.
Slide 13
Environmental Impact :
Point 1 : GHG (Green House Gas Emmission)
Extract from the WCD to explain the point: The Commission found that reservoirs
sampled so far by scientists all emit greenhouse gases, as do natural lakes, due to the
rotting of vegetation and carbon inflows from the catchment. The scale of such emissions
is highly variable. Preliminary data from a Case Study hydropower dam in Brazil show
that the gross level of these emissions is significant, relative to emissions from equivalent
thermal power plants.
However, in other reservoirs studied (notably those in boreal zones), gross emissions of
greenhouse gases are significantly lower than the thermal alternative. A full comparison
would require measurements of the emissions from natural pre-impoundment habitats.
More research is needed on a case-by-case basis to demonstrate the capacity of
hydropower to offset climate change.
Point 2 : Reservoirs drown forests i.e.substantial levels of wildlife habitat adversely
affecting wildlife
Point 3 : Reduces biodiversity Many species of fish are lost as intermixing of upstream
and downstream fish species is not possible anymore ith the Dam coming up as an
artificial barrier to any intermixing.
Point 4 : Causes degradation of coastal deltas because of reduction in sediment deposits
slide 14-19
Slide 15
The next 5 slides have been based on the findings of the WCD with regard to planned
versus actual performance of large dams. Therefore there is a need to briefly explain what
the WCD* is.
Slide 16-19
The need here is to emphasise the fact that large dams never seemed to meet the promises
they make. If we look at the next 4 slides the following are often repeated words “fallen
short” “below target” . The slides are more or less self explanatory.
Some of the points that need to come out of this slide or need to be run through when this
slide is presented are :
• Produce electricity - Hydroelectricity is not cheap or clean as is claimed!
- Costs over runs for dams are high – 30% of World Bank funded dams have cost
over runs due to
- Large dam reservoirs produce gases leading to global warming showing hydro
electricity is not clean as claimed
• Supply Water- Canal irrigation through large dams causes :
– Water wastage through mis management
– Salinisation and water logging destroying fertile soil -20% irrigated land is
affected by salinity
– Found to favour large land holders as against small land holders
• Control Floods – Incapable of controlling large floods which when they occur
cause more harm after the dam is built.
Slides 20 through 24
Discuss alternatives to large dams
Slides 21-22 (Some useful notes for explaining slide21 given at the end)
Focus on harnessing new, economic and sustainable forms of generating elctricity
Slides 23-24
Focus on changing consumption patterns
* The understanding of what the WCD is needed only around the time slide 12 is used –
but it is used much before in our slide explaining what large dams mean. At this point
only the teacher needs to understand what the WCD is all about.
What is the WCD ?
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World Commission on Dams formed in 1997, started work in 1998 – it was
establishe after various big dams were challenged across the world – th
comission arose to look into the controversial issues related to the
construction of large dams.
Final report brought in Nov 2000
Formed by the World Bank
Composed of 12 independent commissioners including Medha Patekar of the
Narmada Bachao Andolan
Terms of reference :
1- review the development effectiveness of large dams and assess
alternatives for water resources and energy development; and
2- develop internationally acceptable criteria, guidelines and standards,
where appropriate, for the planning, design, appraisal, construction,
operation, monitoring and decommissioning of dams
http://www.damsreport.org/report/wcd_overview.htm
Some useful notes to explain slide 21 if need felt :
1- What is a micro hydel project?
Small Scale Hydro Power
Hydro power is available in a range of sizes from a few hundred watts to over 10GW. At
the low end of the spectrum, small hydro power can be divided into three categories. The
definitions of the categories vary, but are broadly: micro (less than 100kW), mini
(100kW-1MW) and small (1MW-10MW) hydro [8]. This section focuses on micro-hydro
systems, which are generally stand-alone systems, ie they are not connected to the
electricity grid.
Micro-hydro systems operate by diverting part of the river flow through a penstock (or
pipe) and a turbine, which drives a generator to produce electricity (see Fig.7). The water
then flows back into the river. Micro-hydro systems are mostly "run of the river" systems,
which allow the river flow to continue. This is preferable from an environmental point of
view as seasonal river flow patterns downstream are not affected and there is no flooding
of valleys upstream of the system [9]. A further implication is that the power output of
the system is not determined by controlling the flow of the river, but instead the turbine
operates when there is water flow and at an output governed by the flow. This means that
a complex mechanical governor system is not required, which reduces costs and
maintenance requirements. The systems can be build locally at low cost, and the
simplicity gives rise to better long term reliability. However, the disadvantage is that
water is not carried over from rainy to dry season. In addition, the excess power
generated is wasted unless an electrical storage system is installed, or a suitable ‘offpeak’ use is found.
Figure 7 A low-head micro-hydro installation
(Image adapted from Stockholm Environment Institute [10].)
Micro-hydro systems are particularly suitable as remote area power supplies for rural and
isolated communities, as an economic alternative to extending the electricity grid. The
systems provide a source of cheap, independent and continuous power, without degrading
the environment.
It is estimated that in 1990 there was an installed capacity worldwide of small hydro
power (less than 10MW) of 19.5GW [8].
There are two main types of turbines used in micro-hydro systems, depending on the flow
and the head, namely impulse turbines and reaction turbines. Typical impulse turbines are
the Pelton wheel and the Turgo wheel, and these are generally used for medium to high-
head applications. Reaction turbines are generally used at low (propeller turbine) or
medium head (Francis turbine) [10].
Electrical energy can be obtained from a micro-hydro system either instantaneously or
through a storage system. In an instantaneous power demand system, the system provides
240V AC power to the load via a turbine which must be sufficiently large to meet the
peak power demand. These systems require a large head and/or flow. In a storage system,
the micro-hydro generator provides a constant DC charge to a battery system, which then
supplies power to the load via an inverter. The battery system must be sized to the daily
electrical demand. However, the turbine is significantly smaller than for an instantaneous
demand system, and it operates at a constant power output.
(From AID India website http://www.aidindia.org/tamu/bilgaon/ )
2- What is pedal power ?
Pedal Power is a cheap way of obtaining power in a developing country such as India. A
single machine costs about $100 (Rs 4000) , including a battery pack. This renewable
source compares very favorably with approximately $10 (Rs 400) paid by every family
each month for kerosene and dry cells. In terms of performance, initial versions
generated 40 Watts. Current versions of the machine provide about an hour of 70 Watts
energy for 15-20 minutes spent pedaling. Being used in the Narmada valley where
struggle against the large Sardar Sarovar dam is ongoing.