Damming even more free-flowing rivers is not a necessary climate tradeoff

The latest report from the Intergovernmental Panel on Climate Change (IPCC), released Monday, offers an ambitious vision for how the world can secure a stable climate. But that vision incorporates a largely unexamined — and now unnecessary — cost to nature and people: the loss of many of the world’s remaining free-flowing rivers.

The energy pathways that the IPCC uses to show how the world can hold warming to the 1.5 degrees Celsius target feature a large expansion of hydropower around the world, with most models including increases of 50 to 100 percent from today’s global capacity. Other influential international organizations, such as the International Energy Agency and the International Renewable Energy Agency, also forecast that a climate solution requires doubling global hydropower by 2050.

But developing that level of hydropower would mean the damming and fragmentation of biologically and economically critical rivers like the lower Mekong, Irrawaddy and the Amazon’s main tributaries. Damming these rivers would result in dramatic negative impacts to communities and the loss of globally important ecosystems — and all to generate less than 1 percent of the total renewable electricity needed to meet the 2050 climate targets.

Hydropower has already contributed over the last century to the fragmentation of two-thirds of the world’s major rivers, a leading driver of the catastrophic 76 percent decline in migratory fish populations, which comprise a particularly important component of river fisheries that still feed hundreds of millions of people worldwide. Further, the reservoirs behind dams trap the sediment needed to sustain economically vital river deltas, which are home to 500 million people and are among the most productive agricultural regions on Earth. Without that sediment, many heavily populated and agriculturally crucial deltas — including those of the Nile and Mekong — are sinking and shrinking.

Including major hydropower expansion within climate solutions might have made sense early this century when renewables such as solar and wind were still in their infancy and hydropower was often the only large-scale renewable option.

But today, the renewable revolution — featuring dramatic drops in cost for wind and solar PV generation — means that countries no longer must choose between preserving their rivers and low-carbon electricity. The cost of solar PV has declined nearly 90 percent in just the last decade. Those drops in cost, coupled with advances in batteries and other energy technologies, mean that countries now have the option of building reliable, low-cost grids without damming any more major rivers.

This doesn’t mean that hydropower won’t be needed, but it must be strategic. Certain types of hydropower can help “firm up” the variability of wind and solar power, facilitating greater proportions of those technologies on the grid. But much of this role can come from existing hydropower or pumped storage hydropower projects, which function like batteries and can be built away from rivers. In contrast to the energy models that assume hydropower capacity will double, there are global models that meet 2050 climate targets with one-quarter of that level of expansion.

We can also derive substantial energy from hydropower investments that don’t require new dams. Refurbishing and modernizing old hydropower plants can increase their generation by up to 30 percent. Turbines can be added to dams that currently lack them. For example, hundreds of megawatts of hydropower have been added to lock-and-dam navigation structures on the Ohio River over the last decade. All of these investments provide additional generation of low-carbon electricity with no additional impacts on rivers.

Provisions in the 21st Century Dams Act, passed last fall by Congress as part of the bipartisan infrastructure bill, provide an excellent model for making climate-smart investments in both hydropower and rivers. This features tax incentives for adding turbines to non-powered dams, modernizing older hydropower dams to increase their generation, and making other changes to improve dams’ environmental performance as well as their contributions to renewable grids. Because the U.S. has tens of thousands of aging and deteriorating dams (generally non-powered ones), these provisions also support removal of obsolete dams to restore free-flowing rivers.

Rather than pursuing a massive expansion in new hydropower dams — projects that have become increasingly risky investments — energy planners, decision-makers and investors in other countries should focus on the types of projects supported by the 21st Century Dams Act and strive to optimize the role of hydropower within well-planned renewable grids. Now that we have the capability to stabilize the planet’s climate and maintain its vital, productive rivers at the same time, it’s clear that doubling global hydropower capacity would exact too heavy a price from rivers and people, for far too small a contribution to the climate solution.

Jeff Opperman is World Wildlife Fund’s (WWF) global lead freshwater scientist.