Why Large Dam Storage is Not the Right Option for Climate Resilience

Zachary Hurwitz

More freshwater is available from green sources such as this organic agriculture field than from blue sources such as large dam reservoirs.
More freshwater is available from green sources such as this organic agriculture field than from blue sources such as large dam reservoirs.

Yesterday afternoon in Marseille, I was invited to go toe-to-toe in a debate of the World Water Forum with seven public figures from the World Bank, Odebrecht Energy, UNESCO-ICIWaRM, Harvard University, WWF, and the governments of Uganda and India regarding the role of water storage in increasing climate resilience. The debate was moderated by Peggy Hollinger of the Financial Times, and was heavily weighted towards proponents of large dams. But here's why large dams are not the right option for climate resilience.

First, because there are high uncertainties as to when and where rain might fall, dams are one of the most vulnerable types of infrastructure to climate change. Even a 2011 World Bank report recognized that "long-lifespan infrastructure, such as hydropower plants, is generally less adaptable to changes whereas short-lifespan infrastructure can be replaced in the long term as the climate changes." The report warned that "heavy reliance on hydropower creates significant vulnerability to climate change."  As an example, Tanzania's power sector was seriously affected by drought in recent years because it is so dependent on hydropower. The IMF advised that the country become less dependent on hydropower as a result.

Second, the hydropower sector has been one of the sectors most at risk of cost overruns. While some debaters attempted to paint this as a myth – including Gabriel Azevedo of Odebrecht – the fact is that the financial, social and environmental costs of dams often reaches three, four, or even many more times the estimated project cost. China is currently building its South-North Water Transfer Scheme to send water to the dry North at a whopping cost of US$62 billion dollars. More than 300,000 people have already been displaced during construction of the canals alone. And the cost has not been worth it. 2011's drought left so little water in the Southern reservoirs that no water could have been sent to the North even if construction of the canals had been completed.  The $62 billion price tag could have been better spent on water conservation and efficiency measures, avoiding the massive social and environmental impacts.

Third, as Swedish hydrologist Malin Falkenmark has shown, more freshwater is available as green water (in fields and plants) than as blue water (in rivers and lakes). Water can be stored through techniques that maintain soil humidity, underground in aquifers, in local ponds, and in small reservoirs. Indeed, John Briscoe of Harvard (and formerly of the World Bank) admitted that in Britain, the majority of freshwater has been obtained from off-stream storage for hundreds of years. In India, the majority of irrigation and water supply is obtained through groundwater. And given the high uncertainty of precipitation in the Himalayas, extreme events such as glacial lake outburst floods (GLOFs) and high precipitation can result in high soil erosion, which causes greater silt build-up in large dam infrastructure, a safety risk for communities downstream.

Lake Turkana in Kenya faces severe drought if more dams are built on the Omo River
Lake Turkana in Kenya faces severe drought if more dams are built on the Omo River

Some of the panelists on the debate deflected serious questions about the long history of corruption that the hydropower sector faces. Suresh Prabhu, former Minister of Power of India, and John Briscoe of Harvard University sustained that dams are not a source of corruption and that some mid-income countries have higher standards than institutions such as the World Bank. Meanwhile, others took to sending pot-shots by whipping up populist sentiment that NGOs are somehow conspiring to impede development. Rachel Kyte of the World Bank admitted, in contrast, that the World Bank Group is better off as an institution, and has stronger project standards, precisely because of the decades of "being forced by civil society to look at issues that were not in the mindset of management."  

There are better options for climate resilience beyond large dam storage. Groundwater storage can be achieved with many small decentralized recharging structures and rainwater harvesting. Another huge source of water storage is soil moisture. One of the best ways in which soil moisture retention can be increased is by switching over completely to organic farming and organic fertilizers. This has a double advantage – it avoids the use of chemical fertilizers, mostly derived from fossil sources thus reducing carbon emissions, and an enhanced soil moisture regime gives much better resilience to crops, especially in the face of increasing temperatures.

It's clear that large dams are not a solution to securing water and energy access in a world of highly unknown climate outcomes. Countries that put all of their eggs in one basket will become more – not less – vulnerable to the vagaries of climate change. There are more cost-effective, safe, and efficient solutions for today's warming world.