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Green economies can flow from strategic hydropower

We sat down with Natural Capital Project’s Rafael Schmitt to discuss his recent work, a new award, and emerging hydropower research frontiers.

Rafael Schmitt is a hydrologist at the Natural Capital Project, where he’s focused much of his work on strategic hydropower planning in the Greater Mekong region, home to the Mekong River, which is shared between China, Myanmar, Laos, Thailand, Cambodia, and Vietnam. The region also includes Myanmar’s Chindwin and Irrawaddy rivers.

This month he’ll receive the Aspen Institute Italia Award alongside three co-authors on a study in Nature Sustainability. Here, he discusses how hydropower, when planned with care, can be an important stepping-stone towards a more sustainable energy system.

mekong river
In the Greater Mekong region, 17 million people depend on rivers for food and livelihoods. Rivers provide people with drinking water, irrigation for crops, habitat for fisheries, recreation opportunities like swimming and boating, and important cultural benefits. Photo Credit: tieanguy / Pixabay

Why is understanding the connectedness of river systems so important to hydropower planning?

Rafael Schmitt: People depend on water in so many ways. Rivers provide people with drinking water, irrigation for crops, habitat for fisheries, recreation opportunities like swimming and boating, and so many important cultural benefits. They also can provide a tremendous amount of energy through hydropower.

Hydropower dams can play an important role in helping developing economies transition to a cleaner energy system that also meets the needs of their people. But the environmental externalities — the side effects — of dams can be catastrophic.

The United States and Europe have so many examples of the damaging side effects of dams, from the collapse of fisheries in the United States’ Pacific Northwest to loss of biodiversity and livelihoods in the Colorado River and Delta. These examples foreshadow what could happen in many developing countries if dams aren’t planned strategically.

The goal of my work is to build our understanding of the connectivity of river systems to show the benefits they provide to people. When we can highlight those benefits, we can help countries make hydropower development decisions that are smarter and more sustainable.

Your work focuses on sediment in river systems. How does sediment provide benefits to people?

Sediment is the term we use for all kinds of solids that are transported by water — sand, silt, gravel and more. When water transports sediment, it defines the shape of a river channel, creating aquatic habitat and enabling people to access the water and other benefits that rivers provide.

In the ecosystem services world, sediment has traditionally been framed as a problem, because too much sediment can smother stream beds and destroy fish habitats. Such an overload of sediment is often the result of poor land management practices like large-scale agriculture and deforestation. Sediment is beneficial to people — you just need the right amount of it.

How does hydropower hinder the benefits that rivers and sediment provide to people?

When you install a new hydropower dam, it creates a cascade of impacts. Fish habitats are disrupted or destroyed, natural irrigation waters are blocked, and sediment stops flowing to downstream communities.

For coastal communities, sediment supply is especially critical in combatting climate change. Rising sea levels and extreme storm events are constantly and increasingly eroding shorelines. It’s estimated that 500 million people live less than 10 meters above sea level. By 2050, that number is expected to rise to one billion people. If a dam cuts off the sediment supply to those coastal communities, their shores will quickly erode into the sea. Keeping natural sediment supply flowing from river basins to coasts is a crucial as a nature-based solution to combat climate change.

We also see significant damages to livelihood and culture because of hydropower development. In the Pacific Northwest, where salmon fisheries were destroyed by hydropower dams, the impacts on the Native American population were particularly damaging. Many fishing communities on the Mekong have very similar fisheries and livelihood practices to those of the Native American communities on the Colombia River, before they were lost to a cascade of major hydropower dams.

Hydropower dams often disproportionally impact communities that are already overburdened. Those communities don’t have another way to replace the lost nutrition, the lost job, and the loss of traditional fishery-related culture.


Much of Schmitt’s work has focused on the downstream effects of hydropower dams, but now he’s turning his focus upstream. His goal is to make current dams for effective through more comprehensive land management and strategic planning for the future. Photo Credit: Richard Cronin, Stimson Center

Hydropower dams can play an important role in helping developing economies transition to a cleaner energy system that also meets the needs of their people. But hydropower’s environmental side effects can be catastrophic. Photo Credit: Richard Cronin, Stimson Center

Why did you choose the Greater Mekong region for your work?

There are few other river systems in the world where sediment is so important. 17 million people live in the Mekong Delta, only a few meters above sea level. They depend on rivers for food and livelihoods, and sediment to keep their shores stable and their river channels deep enough for fish.

Southeast Asia is in a unique position right now, because renewable energy technology is rapidly improving at the same time the region is developing new energy markets. Even in the past two years, we’ve seen the technology with photovoltaic solar increase dramatically. In 2019, I wrote a comment in Nature with some colleagues that focused on the aspiration that solar power might soon be cheaper than hydropower. Just this year, bids on a major photovoltaic project were less than four cents per kilowatt hour, while hydropower is more like six to eight cents per kilowatt hour.

What does the rapid development of photovoltaic solar energy mean for hydropower development?

It means that countries can meet energy needs in a more sustainable, more strategic way. For example, in a place that may have required development of 50 hydropower dam sites a few years ago, now they could choose to develop just five dams. They can supplement the five dams with other renewable energies, like solar, to meet their energy needs. That means those five dams can be chosen strategically, so they have the least environmental impact and provide the highest energy benefits.

Of course, solar energy also has its impacts, so we need to factor those into the equation. A great benefit of solar is that it can be decentralized — it doesn’t need to be placed all in the same spot. Plus, it can be on land that has very little conservation value, like over parking lots or in highway medians. When you compare that with the massive infrastructure space involved in building a new dam, it shows a clear advantage.

How can countries use your process to start strategically planning for hydropower development?

First, the country or region needs to determine how much hydropower they require to meet the needs of their population. They decide what the mix of renewable energy systems might be, likely with solar power as a main source and hydropower as a backup for the times the sun isn’t shining, like nights and cloudy days. Second, we use our river basin models to determine the trade-offs for each combination of energy system. We know we need a certain amount of hydropower, so we use numerical methods to identify combinations of dam sites which would create the least cumulative negative impacts on the environment and people while also providing enough energy.

Countries are becoming more and more willing to embark on this kind of process because of the newer alternatives to hydropower. The countries in Southeast Asia are innovating rapidly. They have less infrastructure in place right now, so they have an opportunity to make different strategic decisions. They can look at Europe and the United States, see the legacy of dams and energy systems that have irreversibly damaged ecosystems, and choose to take a more sustainable path.

Sometimes, the answer might be not to develop new dams inside the country, but instead to import hydropower energy from somewhere else. The Mekong starts flowing in China, where many dams have already been built and created environmental impacts. One solution for downriver countries might be to pay to import energy from China, rather than building new dams in healthy river ecosystems. At the same time, China might agree to pay downriver countries for the loss of fisheries related to the dams they’ve built. It’s a complex political problem because of the number of countries involved and legacies of conflicts around water resources in the basins, but having these conversations can help develop better policies.

What’s next for your research?

A new research frontier of mine is focused on the upstream side of dams. Much of this past research has looked at how dams influence downstream ecosystems and people, but hasn’t focused much on the upstream.

When you build a dam, you need to manage the land surrounding the reservoir in addition to the reservoir itself. If too much sediment is flowing down into a dam’s reservoir, that’s going to increase operation and maintenance costs because it’s constantly filling up. Deforestation and aggressive agricultural practices can contribute to increased sediment and decreased dam efficiency. The more power you can generate from an existing dam, the less need there is for building more dams. So, how can we make current dams more effective by better managing the land around them?

We’re exploring ways to plan across river and landscape domains to have an integrated vision of hydropower management that benefits people and sustains critical ecosystems.

If you’re interested in learning more about Schmitt’s strategic hydropower work, read his papers:

  1.  R. J. P. Schmitt, N. Kittner, G. M. Kondolf, D. M. Kammen, Joint strategic energy and river basin planning to reduce dam impacts on rivers in Myanmar. Environ. Res. Lett. 16, 054054 (2021).
  2. V. Barbarossa, R. J. P. Schmitt, M. A. J. Huijbregts, C. Zarfl, H. King, A. M. Schipper, Impacts of current and future large dams on the geographic range connectivity of freshwater fish worldwidePNAS117, 3648–3655 (2020).
  3. R. J. P. Schmitt, S. Bizzi, A. Castelletti, J. J. Opperman, G. M. Kondolf, Planning dam portfolios for low sediment trapping shows limits for sustainable hydropower in the MekongScience Advances5, eaaw2175 (2019).
  4. R. J. P. Schmitt, N. Kittner, G. M. Kondolf, D. M. Kammen, Deploy diverse renewables to save tropical riversNature569, 330 (2019).
  5. R. J. P. Schmitt, S. Bizzi, A. Castelletti, G. M. Kondolf, Improved trade-offs of hydropower and sand connectivity by strategic dam planning in the MekongNature Sustainability1, 96–104 (2018).

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