Hydropower is the world’s leading source of renewable energy and most hydropower projects generate low-carbon electricity. Yet—as highlighted in a recent op-ed in CNN—hydropower is rarely placed in the bin of virtuous renewables alongside wind and solar.
What accounts for this exclusion?
While nearly all energy projects (or any form of development, for that matter) have some negative impacts, the environmental and social impacts of hydropower can be particularly high. These impacts include the displacement of communities by reservoirs, the loss of migratory fish, and the trapping of sediment needed to prevent the sinking and shrinking of downstream deltas—home to hundreds of millions of people and some of the most productive agriculture on the planet.
These multiple conflicts prevent hydropower from joining the ranks of the righteous renewables.
However, hydropower is a critical part of many countries’ existing power systems and it provides 16% of all electricity globally. Thus, it is a crucial part of the renewable energy present but, in terms of negative impacts, it can do better.
Indeed, hydropower has to do better, because will be a major player in the renewable energy future. Hydropower is projected to continue expanding—by how much is debatable, discussed further below—but, regardless of how much it expands, it provides a range of benefits to grids that can be highly complementary to variable sources, such as wind and solar. So, how can hydropower do better?
This past fall, two journal articles highlighted one key approach for hydropower to do better at avoiding or reducing conflicts: look beyond individual projects and find solutions at the scale of hydropower systems or river basins (full disclosure, I was lead author on one of these articles and a co-author on the other).
The first article, published in Frontiers in Environmental Science, focused on case studies of improved environmental performance of dams, including those that provide hydropower. The common thread in these case studies was that the improved environmental outcomes were achieved through policies or management actions directed at the scale of systems, such as a set of dams within a river basin.
For example, on the Penobscot River in Maine, the removal of two dams by the Penobscot Restoration Trust will benefit populations of several migratory fish species that use the river, including river herring, which surged from a few thousand before dam removal to well over two million fish after. This dramatic improvement in environmental performance was made possible by an innovative agreement that moved the Penobscot beyond decades of conflict waged over individual dams and, instead, forged a solution to balance hydropower and fish at the scale of the overall system. Following the agreement, two dams were removed, and one completely bypassed, allowing migratory fish to access hundreds of miles of additional habitat. Meanwhile, the hydropower owner received new licenses for the remaining dams. Remarkably, through equipment upgrades and operational changes at those dams, the overall Penobscot system will generate slightly more electricity after dam removal than before, even as the river basin is transformed for the benefit of migratory fish.
This system-scale breakthrough to reduce conflicts on the Penobscot arose through the licensing process overseen by the Federal Energy Regulatory Commission (FERC) – a process not generally associated with system-scale outcomes. While, in theory, FERC license holders can pursue license renewal through system-scale approaches, they almost always do so on a project-by-project basis (the Penobscot process was the unusual product of good timing, consolidated ownership, and stakeholders motivated to push the envelope to break out of a stalemate).
However, in large part based on the remarkable outcomes achieved in the Penobscot, and the positive attention it has received, various entities are now exploring how FERC licensing processes can be used to find “more Penobscots” — system-scale processes with the potential to produce benefits for both rivers and energy. For example, in Wisconsin, there are 12 licensed hydropower projects in the Wisconsin River basin that must renew their licenses by 2026, and eight others needing license renewals in the following decade. The licensees for these 20 projects have submitted requests for comment on their plan to align their relicensing timelines, proposing that coordinated licensing could produce efficiencies for both licensees and regulatory agencies and allow the opportunity to produce “holistic river basin management plans to reduce risk and increase resiliency.”
The second article on system-scale approaches, led by Rafael Schmitt of Stanford and published in Science Advances, highlights how strategic hydropower planning and development can deliver far more balanced outcomes between energy and environmental resources, compared to typical project-by-project development. Thus, while the first article explored how to improve environmental performance of the hydropower present, Schmitt et al’s paper examines the potential for better performance of future hydropower, focusing on the Mekong River basin in southeast Asia.
The Mekong is home to perhaps the highest profile conflicts over hydropower development today, with specific clashes over displacement of communities, changes to river flow patterns, impacts to migratory fish (the foundation for the world’s most productive freshwater fishery) and the trapping of sediment in the reservoirs behind dams. This sediment is vital to the future of the Mekong’s delta in Vietnam, home to approximately 20 million people and some of the most productive agriculture in Asia. Continued development of dams that trap high volumes of sediment would considerably increase the vulnerability of the Delta to rising sea levels and other threats.
The hydropower dams already developed will trap nearly 70% of the total available sediment supply in the Mekong basin. Schmitt et al’s analysis shows that a more strategic approach to hydropower planning—avoiding those dams with the largest relative impact on sediment—could have achieved the same amount of electricity generation but only reduced sediment by 38%, reducing by nearly half the conflict between hydropower and sediment. But that is an opportunity that was lost.
The next set of dams that are moving forward would, if completed, result in nearly complete capture of the basin’s sediment supply, essentially sealing the fate of the Mekong Delta to slip beneath the ocean. But the analysis of Schmitt and colleagues again shows that a more strategic approach to future dam development—mainly, placing new dams upstream of existing dams—could generate equal or more electricity with nearly no additional loss of sediment.
Both of these articles emphasize the benefit of moving the search for solutions beyond individual projects and toward hydropower systems. But the potential for more balanced outcomes by expanding scale is not restricted to hydropower systems – further gains can be made by finding solutions at the scale of overall energy systems, that extend beyond basins to regional or even continental scales.
Most current energy projections, such as those contained within most scenarios used by the Intergovernmental Panel on Climate Change (IPCC), forecast a near doubling of today’s global hydropower capacity. Even with the best system-scale planning, preliminary analysis suggests that level of development would require damming most of the world’s remaining free-flowing rivers.
But the renewable revolution opens the possibility of avoiding the conflicts that would arise from that scale of loss of healthy rivers globally. In the report Connected and Flowing, WWF and The Nature Conservancy illustrated the potential for the world to meet climate targets with a minimal loss of free-flowing rivers. This potential arises from the renewable revolution – the rapidly falling costs for wind and solar generation and storage technologies, alongside significant advancements in energy efficiency, demand side management, and grid management.
Continued progress on these technologies could reduce the total need for hydropower, particularly those projects that would dam the remaining free-flowing rivers or those rivers, such as the Mekong, that have some existing dams but retain immense environmental values that benefit tens of millions of people.
In contrast to those of the IPCC, some forecasts anticipate far lower expansion of hydropower globally (e.g., 300 GW of additional capacity rather than 800 GW) and recent trends in investment suggest these lower forecasts may indeed be realistic.
In Connected and Flowing, we showed that a lower total development of hydropower, combined with system-scale approaches to planning and siting dams, could reduce hydropower impacts on rivers by 90%.
This expansion of scale for planning, development and/or operation—moving from individual projects to river basins and then to grids and regions—holds great promise for the world to achieve future power systems that are low cost, low carbon and low conflict (LowCx3).
Achieving a LowCx3 future will require a range of policies and financial mechanisms, which I’ll explore in future posts.