Module VI - part II

The problems with dams

What's wrong with dams?
Dams can have devastating effects on rivers, freshwater ecosystems, and the people who depend on them.
Dams are built to irrigate crops, generate energy from hydropower, improve navigation, control floods, and supply water. But when they aren’t built or operated appropriately, they can ravage rivers and destroy livelihoods.
Very few of the world’s rivers now run uninterrupted from their source to the sea.
The world’s rivers are at risk. Fragmentation of rivers affects the migration of fish, disrupts the transport of sediments, cuts off floodplains from life-giving floods, and threatens many endangered species. Environmental problems extend throughout the river basin.
Dams can destroy livelihoods
The devastation of freshwater ecosystems directly affects the livelihoods of millions of people who live upstream and downstream of dams, especially in developing countries. And this is in addition to the large numbers of people that are relocated to make way for the reservoirs.
…and their costs often outweigh their benefits
Dams are expensive and the projected financial costs are often inaccurate. The benefits are often overestimated, driven by the incentives of politicians, developers, contractors, consultants, and banks to implement new projects. And since, most of the world's dams are now being built in developing countries, it is even more important that a project makes economic sense.

Dams can cause significant environmental damage.
When a dam is constructed, be it for hydropower or water supply, the destruction is highly visible. But the environmental impacts of a dam stretch much further downstream than the location of the actual dam site.
Facts
•    Worldwide, the amount of water stored in reservoirs behind dams is 3 to 6 times the quantity contained in rivers.
•    It is estimated that wetland areas decreased in extent by 50% during the 20th century.
•    More than 20% of the world’s 10,000 recorded freshwater fish species have become extinct, threatened, or endangered in recent decades.
Dams block migratory fish species from their spawning and feeding sites.
Fish ladders have been successful to some extent for species such as salmon. But they are not always effective and are not a viable solution for many tropical rivers.
Dams disturb natural fluctuations in water flow.
This can be particularly damaging in seasonal floodplains, affecting deposits of nutrients as well as the lifecycles of species that depend on these fluctions for feeding and breeding grounds. Dams change daily flows by releasing water as a reaction to human demands, like energy and irrigation, instead of as nature intended.
Water quality can be degraded.
Reductions in water quantities can increase salinity and make the water unusable for drinking and irrigation. Decomposition of organic matter and the leaching of mercury from the soil can introduce toxins.
The transport of sediment along the river is disrupted.
This affects the morphology of the riverbed, downstream floodplains, and even coastal deltas. In turn, this can:
•    increase flood risk
•    hamper navigation
•    lower groundwater tables
•    cause an accumulation of toxic materials
•    affect entire ecosystems.
The buildup of sedimentation in the reservoir also reduces the dam's capacity and operational lifetime.
Reservoirs can emit climate-changing greenhouse gases.
Particularly in tropical areas, the release of carbon dioxide (CO2) and methane as flooded trees and plants decompose is a serious cause for concern that needs more investigation.
Dams are not always bad news for all species.
Once reservoirs become established they can become important sites for birdlife. Out of 1,345 wetlands of international importance under the Ramsar Convention, about 100 are artificial, many of these being water storage areas.
Some dam projects have implemented specific habitat restoration measures that can to some extent compensate for their negative impacts.

Dam problems - Social impacts
Dam good plans do not always make good practice
The socio-economic benefits of dams are numerous and in many places dams have undoubtedly contributed to economic development.
Many countries would look different today without hydroelectricity, irrigation, water supplies, flood control, and recreational activities around reservoirs.
But the negative socio-economic impacts of dams should be taken into account, too. As more and more dams are built in populated areas of developing countries, the scale of the social and economic effects is growing.
Endangered livelihoods
The disruption of natural ecosystems, particularly of floodplains, threatens the livelihoods of the millions of people downstream of dams who depend on fisheries, wetlands, and regular deposits of sediment for agriculture.
Displacement of people
An estimated 40 to 80 million people have been displaced by dams worldwide. Yet mitigation, compensation, and resettlement attempts are often inadequate. WWF believes that directly affected people should be engaged in a transparent decision-making process. And we support the recognition of the right to free, prior, and informed consent for indigenous peoples.
Health
Improved access to clean water is a major benefit of dams. But the habitat they create is perfect for disease-carrying mosquitoes and snails, which bring illnesses such as malaria and schistosomiasis. Social disruption and higher population densities in resettled communities can result in poor hygiene and a host of related diseases.
Damage to cultural heritage sites
In many places, large dams have impacted cultural heritage by the submergence and destruction of cultural resources such as shrines, buildings, artifacts, burial sites, and sacred landscapes.
Dam problems - The financial costs
Dams are expensive. And not all the costs always show up on paper.
Fast Facts
•    The World Commission on Dams found the average cost overrun of 81 large dam projects to be 56%.
•    One MW of hydropower costs about US$1.5 million to install.
•    For the same amount of money, 15,000 people could be given access to clean drinking water for the first time.
They're dam expensive
Dams are expensive. And their benefits are often over-estimated, while their costs are downplayed.
Many projects suffer from over-optimistic benefit projections, which make them seem more financially attractive than they really are.

At the same time, the potential risks, such as the impacts of climate change and the local political situation, are often under-estimated.
Costs for people indirectly affected also need to be factored in.
For example, downstream communities may lose their income from fisheries or have reduced harvests due to interruptions in the river's flow.
Instead of only looking at the financial return on investment, governments, regulators, and development banks must look at the overall return to society.
Seen in that light, the economics of many dams look doubtful.
Which way to development?
It's clear that many countries, particularly in Africa and South Asia, will need more water infrastructure.
But given the level of expenditure involved, each project requires individual scrutiny and serious attempts to optimize its location, design, and operations. Claims that a dam will alleviate poverty, provide water and energy security, and help a country adapt to climate change, need to be confirmed in a transparent planning and decision-making process, in which different development options are compared.