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The Environmental and Social Impacts of Large Scale Dams: 

The Environmental and Social Impacts of Large Scale Dams By: Brandon Sorenson Image from:

~ Patrick McCully ~: 

~ Patrick McCully ~ “Massive dams are much more than simply machines to generate electricity and store water. They are concrete, rock and earth expressions of the dominant ideology of the technological age: icons of economic development and scientific progress to match nuclear bombs and motor cars.”


Introduction This presentation focuses on the negative impacts of large scale irrigation and hydroelectric dams from both an environmental and a social perspective. It is designed to describe how dams effect their surrounding physical environment, as well as their social impact on local people and their cultures. To do this, it focuses on the lifecycle of freshwater extraction at it largest scale: through the use of gigantic concrete mega-dams.


Life on this planet has evolved around the availability, movement, and quality of water. Like every other living being on this planet, water is essential for human survival. Because of this, civilization has traditionally been structured around the natural spatial arrangement and flow of water systems. From nomadic trade routes that travel from oasis to oasis, to large modern port cities and blooming desert metropolises, humanity is inseparably linked to water.

Dam Uses: 

Dam Uses Direct Water Usage: Private / Domestic - Household purposes, Drinking water and landscape irrigation Commercial - Restaurants, hotels, golf courses, etc. Irrigation – Crop use. Water needs at the scale that large dams provide most often feed industrial farming practices. Livestock – Use for animal raising as well as other on-farm needs Industrial – Cooling water (power generation, refineries, chemical plants), processing water (manufacturing; pulp and paper, food, high tech, etc.) Mining – hydraulic mining, various processes, settling ponds General public supply – Firefighting, public parks, municipal office buildings

Dam Uses: 

Dam Uses Indirect Uses: Hydroelectric Power – Power generation is one of the most common purposes for the construction of large dams. It is promoted as a totally “clean” form of electricity. Flood Control – Dams even out the peaks and lows of a rivers natural flow cycle by calming seasonal flooding, then storing that water for gradual release year round. Transportation – Dam locks are used to move ships past large dams. This in conjunction with flood control make transportation feasible on rivers that were traditionally wild.

Distribution of Water Resources: 

Distribution of Water Resources Global distribution of water resources varies greatly by region. Climate, topography, geology, hydrology, upstream water usage, and historic water usage all come into play in determining the availability of water in any given region. From:

Distribution of Water Resources: 

Distribution of Water Resources This is not to say that everyone in these water rich areas has consistent, affordable, quality water that is assured to them. Peru, The Democratic Republic of the Congo, and Myanmar are examples of this From:


Hmm . . . Those countries sure seem to have a lot of water, why don’t they just build lots of large dams to fix their problems?? Well, you see Mrs.Dial, It’s not quite that simple. But with lots of large dams they could provide water for their thirsty masses and clean electricity to fuel industrialization! Everyone would benefit, it would be fabulous! Oh boy . . . I think we better start at the beginning . . .

Types of Large Dams: 

Types of Large Dams Large dams are built using several different methods. For the purpose of this project I will investigate the three main types of dams that can be built at extreme scales. These types are: Gravity dams Arch dams Buttress dams

Gravity Dams: 

Gravity Dams Gravity Dams use their triangular shape and the sheer weight of their rock and concrete structure to hold back the water in the reservoir. From:

Gravity Dams: 

Gravity Dams Gravity dams are the most common type of large dam in the world because they are easy and cheap to build. They can also be built across long distances over relatively flat terrain. This makes them very applicable in non-mountainous regions. The largest gravity dam in the world is the Aswan Dam in Egypt. (24)

Arch Dams: 

Arch Dams Arch Dams utilize the strength of an arch to displace the load of water behind it onto the rock walls that it is built into. From: From:

Arch Dams: 

Arch Dams Arch dams can only be built where the walls of a canyon are of unquestionable stability. They must also be impervious to seepage around the dam, as this could be a source of dam falure in the future. (24) Because of these factors, Arch dams can only be built in very limited locations. Arch dams use less materials than gravity dams, but are more expensive to construct due to the extensive amount of expertise required to build one. (25)

Buttress Dams: 

Buttress Dams Buttress Dams use multiple reinforced columns to support a dam that has a relatively thin structure. Because of this, these dams often use half as much concrete as gravity dams From:

Composite Dams: 

Composite Dams Composite dams are combinations of one or more dam types. Most often a large section of a dam will be either an embankment or gravity dam, with the section responsible for power generation being a buttress or arch.


The Bloemhof Dam on the Orange River of South Africa is an excellent example of a gravity/buttress dam. From: Gravity Dam Buttress Dam


Wow! That’s great, now you’ve shown me all the amazing techniques that I need to bring fresh water to those people!! Yahoo! Let’s Go! Hold on there everyone! You see, there are quite a few environmental and social problems associated with these here dams . . . Lets start with the materials that they’re made of


Materials Large amounts of soil, sand, stone and aggregate and concrete are need for dam construction. If available, these materials will be collected as near to the site of the dam as possible. The extraction of these materials requires large amounts of fossil fuels to operate the machinery. Air and water pollution result from the dust and mud that is created from this process

Materials continued: Concrete: 

Materials continued: Concrete Concrete is the primary ingredient in any large scale dam. Concrete is basically a mixture of two components: aggregates and paste. The paste is usually composed of Portland cement and water, and it binds together the fine and coarse aggregates. (20) A typical mix is about 10 to 15% cement, 60 to 75% sand/ aggregate, 10 to 20% water and 5 to 8% air. (20) Producing one ton of cement results in the emission of approximately one ton of CO2, created by fuel combustion and the calcination of raw materials (21)

Physical Impacts of Large Dams: 

Physical Impacts of Large Dams The physical impacts of large scale dams fall into several categories Upstream On-site Downstream Global Scale

Physical Impacts: Upstream: 

Physical Impacts: Upstream Loss of Land Destruction of peoples property in the reservoir zone. Loss of possible agricultural, range or forest lands. Stagnant Water Table: Water from unnatural reservoirs seeps down into the water table. This excess water can overload the natural watertable, slowing down its flow, so that it ultimately may go stale. This can be damaging to surrounding flora, and has the potential to harm the well water of surrounding peoples. Habitat Destruction : The area that is covered by the reservoir is destroyed, killing whatever habitat existed there beforehand. Habitat destruction also happens far upstream from a dam. Migratory fish can no longer travel upstream past large dams in order to reach their spawning grounds.

Physical Impacts: On-site: 

Physical Impacts: On-site Change in Water Characteristics Temperature – Large reservoir of water heat up as more water is exposed to the sun for longer periods of time. Aquatic life that is sensitive to temperature cannot adjust to this change in their aquatic climate. Salinity – The rise in a rivers salinity due an unnatural reservoir is due to increased evaporation rates. Sediment Load – Sediments that wash down the river settle into large reservoirs. In rivers that have high sediment loads this usually determines the life Nutrient content – Natural nutrients build up in reservoirs, causing eutrophication. O2 content – each of these elements results in a lower oxygen content, further harming aquatic life.

Physical Impacts: On-site: 

Physical Impacts: On-site Dust, Noise pollution from Construction Water Pollution Industrial and residential pollutants, as well as agricultural runnoff (including high nitrate loads, fertilizers and pesticides). On lake sources such as boats and jet skis add oil and other chemical pollutants to waste water. These chemicals build up to toxic levels in reservoirs, especially during dry seasons when little water leaves. Habitat Destruction Loss of local ecosystem covered by the reservoir. Damage caused by improved access to humans: roads, transmission lines, increased migration

Physical Impacts: On-site: 

Physical Impacts: On-site Exotic species introduction Aggressive, non-native species of fish are often introduced to reservoirs for farming and sport fishing. Disease Vector borne diseases increase in tropical areas due to the creation of large areas of still water. This encourages mosquito breeding, the main vector for the transmission of malaria and dengue. Schistostomaiasis is a water borne disease that comes from snails that breed on the upstream side of dams.

On-Site Impacts:Reservoir-Induced Seismicity: 

On-Site Impacts: Reservoir-Induced Seismicity There is a correlation between the creation of a large reservoir, and an increase in seismic activity in an area The physical weight of unnatural reservoirs can cause seismic activity. While not the direct cause of earthquakes, the weight of reservoirs can act as a trigger for seismic activity. Although not much direct research is available on the subject, the proposed explanation is that “when the pressure of the water in the rocks increases, it acts to lubricate faults which are already under tectonic strain, but have been prevented from slipping by the friction of the rock surfaces”. As of now, it is not accurately possible to predict which large dams will produce RIS or how much activity will be produced. Earthquakes that are produced as the result of dams are not usually major, but they still pose a major threat to dam stability and the safety of people living downstream.

Physical Impacts: Downstream: 

Physical Impacts: Downstream Flow Reduction: The downstream impacts of the net flow reduction due to extraction upstream can be extensive. They include habitat destruction far downstream at the mouth of the river, natural water table reduction. Change in water characteristics: The changes in water characteristics that are mentioned above continues in the water that is discharged downstream. The cumulative effect of many dams on a single river magnifies each of these factors.


In Central Asia the Aral Sea shrank by half of its original volume after the Soviets began diverting water for electrical generation, as well as for cotton and other crops. Although this may be one of the most visible example, overextraction of water resources and the resulting drops in local water tables are happening worldwide. From:

Physical Impacts: Downstream: 

Physical Impacts: Downstream Change in natural flood patterns: Natural floods inundate downstream regions with nutrient rich sediments. Traditional farming systems in countries like Egypt (the Nile) and Bangladesh (the Ganges) were dependant upon seasonal floods to wash nutrient rich sediment upon the lower shores of the river. They also seasonally clear out blocked waterways, which prevents larger floods from causing massive damage.



“Named China’s Sorrow for its history of ruinous floods, the Yellow River now barely trickles in its lower reaches – and in recent years has gone dry due largely to heavy irrigation upstream. It’s not alone: The once mighty Nile, Ganges, and Colorado Rivers barely reach the sea in dry seasons.”: 

“Named China’s Sorrow for its history of ruinous floods, the Yellow River now barely trickles in its lower reaches – and in recent years has gone dry due largely to heavy irrigation upstream. It’s not alone: The once mighty Nile, Ganges, and Colorado Rivers barely reach the sea in dry seasons.” China

Social Impacts: Access to Water: 

Social Impacts: Access to Water From:


India Water flows past these squatters in gigantic pipes on its way to high paying customers in Delhi. Where they can, they get water from leaks in the pipe. Otherwise they retrieve it from the Ganges River (in the background). This water is often of substandard quality, and seasonal floods pose the threat of washing out this entire settlement. (10)

Matamoros, Mexico: 

Matamoros, Mexico With no public funds left for waste-water treatment plants, Matamoros’ canal system is filled with raw sewage and industrial pollution. In 2001, the overused Rio Grande dropped below the city’s water intake pipes, leaving the city with no municipal fresh water for almost a month. (10)

Social Impacts: Price of Water: 

Social Impacts: Price of Water From:

A drained aquifer, an inadequate water supply system in its outer regions, and massive amounts of poverty have left Mexico City as one of the most water impoverished metropolitan areas in the world. People are forced to pay almost 200% of what wealthy residents with existing water connections are charged. As shown in this picture, the water is often stored in old barrels that had previous industrial uses. (10): 

A drained aquifer, an inadequate water supply system in its outer regions, and massive amounts of poverty have left Mexico City as one of the most water impoverished metropolitan areas in the world. People are forced to pay almost 200% of what wealthy residents with existing water connections are charged. As shown in this picture, the water is often stored in old barrels that had previous industrial uses. (10) Mexico City

Social Impacts: Quality of Water: 

Social Impacts: Quality of Water From:

Santiago, Chile: 

Santiago, Chile By reducing the need for new water sources, wastewater treatment plants offer a solution to building large dams, for those who can afford it. Worldwide, 2/3 of municipal wastewater doesn’t get treated, much less recycled. Most of it returns to the river system, where many people fish, drink, swim and bathe. An exception to this case is Santiago, Chile, which plans to treat all of its wastewater by 2009. (10)


Displacement When dams are constructed in populated areas, many people are forced to relocate. Established communities are dispersed and often destroyed. The communities that are forced to absorb the influx of displaced people are strained to their maximum capacity. The mass majority of people that are displaced by dam construction are poor. The cost of moving is often placed upon the people being uprooted. This is extremely hard for poor, marginalized people to accomplish, and often leaves them poorer than before. This is especially true for small agricultural communities that, now forced into the urban settlements and its subsequent infrastructure, have no viable job skills in order to provide a living wage for themselves.


Displacement Because of limits to space and resources, people are often forced to move long distances from their original homes. This, coupled with the hard transition into urban areas, often destroys traditional cultures. Because of limits to space and resources, people are often forced to move long distances from their original homes. This, coupled with the hard transition into urban areas, often destroys traditional cultures.

Displacement: India and China: 

Displacement: India and China The problems of displacement are very acute in countries such as the Peoples Republic of China (PRC) and India that are already heavily populated, and have been aggressively building dams since post WWII. An estimated 12.2 million people have been displaced over the last fifty years due to the PRC’s dam building projects (9: a,b). Although the number of new dams being built in these countries has decreased, the size and scale of the projects have been increasing. 1.1 to 1.3 million people are expected to be displaced by the Three Gorges project (9a). With the price tag of the project at an estimated $24.65 billion for the project alone, billions more are going to be spent on resettlement(26).



Social Impacts: International: 

Social Impacts: International International water conflicts occur in regions where rivers cross the borders of one or more nations. Violent conflict has the possibility to occur when one country overdraws its share of the water, causing detrimental effects in the downstream countries Rivers that have ongoing conflicts: The Nile The Ganges The River Jordan The Colorado The Parana

Types of Development: 

Types of Development Developing countries have restructured their economic systems to pay their debt and export their way to prosperity. To do this they are developing their water resources in the direction of rapid industrialization. In this mindset, massive hydroelectric dams are an absolute necessary in order to provide the water and electricity that industries need. In otherwise resource poor countries, this is seen as the only answer to achieve modernization, and to escape their cycle of debt. Once that problem has been met, then issues of water access and quality will be answered, because the country will have moved up to at least a “2nd world” status.

Financial Issues: 

Financial Issues The finance that is needed for the construction of large dams causes many problems around the world; especially in poor, underdeveloped countries that are currently trapped in a painfully binding cycle of debt. Since large scale dams require massive amounts of capital investment, dam construction is one of the primary reasons that countries take out loans from international lending associations. Countries often take out loans to build large hydroelectric dams in order to improve their industrial infastructure. The hope is that by boosting their industrial sector, that they will boost their economy into economic prosperity.

Debt and International Lending Associations: 

Debt and International Lending Associations Depending on the site and the scale of the project, prices for each project varies greatly. Average costs for large projects are usually in the area of billions of dollars (US). For smaller or less developed countries this cost is often more than their annual GDP, and is absolutely insurmountable without the help of outside financing. The World Bank is the greatest single source of funds for large dam construction, having provided more than US$50 billion (1992 dollars) for construction of more than 500 large dams in 92 countries (27)

Water Privatization and Globalization: 

Water Privatization and Globalization “The goal (of water invested corporations) is to render water a private commodity, sold and traded on the open market, and guaranteed for use by private capital through global trade and investment agreements. These companies do not view water as a social resource necessary for all life, but an economic resource to be managed by market forces-like any other commodity.” (12) Corporate shareholders have a legal responsibility to maintain consistently increasing profits and are not concerned about sustainability or equity of water delivery. The concentration of power in the hands of a single corporation and the inability of governments to reclaim management of water services allows corporations to impose their interests on government, thereby reducing the democratic power of citizens.

The Commodification of Water: 

The Commodification of Water “Water promises to be to the 21st Century what oil was to the 20th Century: The precious commodity that determines the wealth of nations” ~ Forbes Magazine, May 2000 ~ (22) From:

Major Water Companies of the World: 

Major Water Companies of the World Suez image: Nestle Image: Vivendi Image: Saur image: Thames Image: Bechtel Image:

Municipal Water Control: 

Municipal Water Control Some of the largest corporations dealing with the development and management of water infrastructures are Vivendi Universal, Suez, Bouygues-SAUR, RWE-Thames, Bechtel-United Utilites, and Nestle (7). At either the request of the government or the insistence of the World Bank, these corporations take over municipal water provision services. The poorer, underdeveloped outlying areas of cities and countries are often neglected. If the country requires that services be provided to these areas, the companies often raise prices to ensure that full cost recovery for their expenses is recovered (6). Once these companies are in control of water systems, water provision becomes commodified. The water is then provided on an ability-to-pay basis.

So . . .: 

So . . .

What should be done?: 

What should be done?


Conservation Using aggressive conservation approaches is one of the easiest and most cost effective ways to eliminating the need for new dams. Replacing old, leaking infrastructures is costly on the front end, and most municipalities in poor countries lack the funds to do it. Different conservation techniques and technologies can be applied to all areas of water use, from industry to agriculture. What lacks in most countries is an incentive to conserve. With state subsidized water flowing to areas of industrialization, it is more costly for companies to conserve water than to waste it. The answer proposed by the neoliberal train of thought is the commercialization of water markets. By being forced to pay for their own water, people turn to conservation to reduce costs. This may work well for certain parts of the industrial and commercial sector, but local people can ill afford to pay for water to be delivered to their homes, let alone improve the leaking pipes in their homes.

Irrigation Techniques: 

Irrigation Techniques Irrigated agriculture uses up to 70% of freshwater in some countries. Nontraditional, Industrial methods often flood fields, loosing much of that water to evaporation. This?

Irrigation Techniques: 

Irrigation Techniques Correctly used, drip irrigation places the exact amount of water where it is needed, when it is needed. This can reduce the amount of water needed for irrigation anywhere from 30% to 70% Or this.

Water Integration and Management: 

Water Integration and Management Instead of providing people with an endless tap, demand side water management provides people with water when they need it in pre-planned quantities. This encourages conservation without raising costs or encouraging commodification. (8) Water Integration refers to integrating water management policies into all levels of society, public and private. This leads to a separation who has power over water utilities, and can serve as a system of checks and balances. (5)

Stop Building Large Dams: 

Stop Building Large Dams The negative social and ecological effects of large scale dam building far outweighs the positive attributes that they bring to society. Instead, small dams should be built, where needed, in the control of those who should have it: the people.


Ecosystem Destruction Fish Blockage and Wildlife Losses Large-Scale Flooding Due to Dam Failures Sedimentation and Salinity Herbicide and Other Toxic Contamination Evaporative Losses Nutrient Flow Retardation Release of greenhouse gasses


45,000 large dams worldwide 2 dams commissioned per day in1970s total investment exceeds $2 trillion $40 billion expenditure per year at peak estimated 40 – 80 million people displaced flow in 60% of world’s rivers affected Number Of Dams 1900 1990s 0 2 000 6 000 4 000

Local Control: 

Local Control Local control of water systems is essential for feasible, equitable, and sustainable water resource development. All decisions about water must be based on ecosystem and watershed-based management. Only through this method will the ecological limitations of watersheds and the damages that dams create be realized. These decisions must be local in origin, as they directly effect the people that live in the watershed and the people that are receiving the water. Having no vested interest in these local concerns, transnational corporations are instrumentally detrimental to the quality, cost and availability of water.

Alternatives and Conclusions: 

Alternatives and Conclusions We may now be facing the greatest challenge of our time. As water is the very centerpiece of life, the fight against the globalization and commodification of water is the centerpiece in the fight for global, universal justice and equity. No partial, conservation oriented solution is going to prevent the collapse of whole societies and ecosystems. A radical rethinking of our values, priorities, and political systems is urgent. There are many ways to assist the developing world in this crisis, the major among these is the cancellation of the Third World debt. Without the crushing load of debt, countries would be able to control their own resources, and would not be forced into models of development that are not right or natural for their country. “Water must be declared a basic human right. This might sound elemental, but at the World Water Forum in The Hague, it was the subject of heated debate, with the World Bank and the water companies seeking to have it declared a human need. This is not semantic. If water is a human need, it can be serviced by the private sector. You cannot sell a human right.” (12)


“We, as human beings, must change our behaviors. We must emphasize identifying the capacity of our watersheds and, as communities, identify the limits we can place upon them. The world must accept conservation as the only model for survival, and we must all teach ourselves to live within our environment's capacity. The insidious problem with pricing and conservation by commodification is that it actually undermines environmental science and activism, as well as governments' responsibility to protect their citizens and the environment by buying into the argument that the market will fix everything. At stake is the whole notion of "the commons," the idea that through our public institutions we recognize a shared human and natural heritage to be preserved for future generations. Citizens in communities around the world must be the "keepers" of our waterways and establish community organizations to oversee the wise and conservative use of this precious resource. Never has there been such an urgent need to come to terms with this seminal issue.” ~ Maude Barlow ~


References Blue Gold: the Fight to Stop the Corporate Theft of the World’s Water. M. Barlow, T. Clarke. The New Press, New York, 2002. The California Water Atlas. Karl, William L. ed. State of California Office of Planning and Research, Sacramento. 1978 Water and Water Policy in World Food Supplies. Articles presented at Texas A&M University on May 26-30, 1985. Texas A&M University Press, College Station, TX. 1987 Cadillac Desert. Mark Reisner. Penguin Books, New York, 1993 Justice and Natural Resources: Concepts, Strategies, and Applications. K. Mutz, G. Bryner & D. Kenney. Island Press, Washington, 2002 Silenced Rivers: The Ecology and Politics of Large Dams. Patrick McCully, Zed Books, London, 1996 The Water Manifesto: Arguments for a World Water Contract. Petrella, Riccardo. Zed Books, London, 2001 “Integrated Approach for Efficient Water Use Case Study: Israel” Saul Arlosoroff, The World Food Prize International Symposium: “From the Middle East to the Middle West: Managing Freshwater Shortages and Regional Water Security”, Des Moines ,Iowa, USA October 24-25, 2002 The World Commission on Dams homepage Country Review Paper: “Experience with Dams in Water And Energy Resource Development In The People’s Republic of China” Case Study: “Large Dams: India’s Experience”


Montaigne, Fen. Challenges for Humanity: Water Pressure. National Geographic. Sept. 2002 (pictures by Peter Essick) The International Rivers Network Official page of the United States Geological Survey USGS Toxic Substances Hydrology Program The official website of the United States Environmental Protection Agency’s Office of Water. EPA Water Quality Inventory Report, 2000. The World Bank’s official home page.

Slide67: The Water Environment Federation homepage. The Water Page The American Concrete Institute Homepage,15114,368262,00.html The University of Durham, UK The Nelson Institute for Environmental Studies, University of Wisconsin – Madison CNN Report on the Three Gorges Dam

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