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Hydropower in the Pan Amazon: A shift toward reduced impact facilities, but the controversy continues

Hydropower facilities with dam and pipeline designs avoid most of the impacts associated with dam, reservoir and run-of-river designs. This image is from Bolivia, of the Corani/Santa Isabel hydroelectric facility. Credit: PAC Collection on

  • Mongabay has begun publishing a new edition of the book, “A Perfect Storm in the Amazon,” in short installments and in three languages: Spanish, English and Portuguese.
  • Author Timothy J. Killeen is an academic and expert who, since the 1980s, has studied the rainforests of Brazil and Bolivia, where he lived for more than 35 years.
  • Chronicling the efforts of nine Amazonian countries to curb deforestation, this edition provides an overview of the topics most relevant to the conservation of the region’s biodiversity, ecosystem services and Indigenous cultures, as well as a description of the conventional and sustainable development models that are vying for space within the regional economy.
  • Click the “A Perfect Storm in the Amazon” link atop this page to see chapters 1-13 as they are published during 2023.

After highways, investments in large-scale hydropower facilities are the most controversial infrastructure investments in the Pan Amazon. Governments pursue hydropower as a sovereign source of renewable energy and driver of economic growth; opponents object due to the environmental and social impacts associated with large-scale projects.

There are elements of truth in both of these affirmations, and the debate surrounding hydropower usually focuses on the trade-offs in the costs and benefits that have caused some projects to be approved, others to be modified and a few to be cancelled.

Historically, Brazil has been overly reliant on hydropower. In the late 1990s, it represented a remarkable ninety per cent of installed generating capacity, a situation that provoked the electricity crisis of 2001/2002 when water levels in reservoirs were reduced by a prolonged nationwide drought. The government responded by diversifying its electrical generation capacity in natural gas, biomass, wind, and solar, as well as by increasing hydropower capacity in Amazonian rivers deemed to be less susceptible to the risk of periodic drought.

Brazil is still overly reliant on hydropower, as evidenced by the weather-induced power rationing that rocked the national economy in 2015. In 2005, the civil engineers within the federal energy agency of Brazil estimated the potential hydropower capacity of Brazil at approximately 251 GW, of which about half was located within the Amazon Basin. By 2020, however, they had reduced that estimate to 176 GW, while reporting that installed capacity had increased from more than 78 to 108 GW; most of that expansion had occurred within the Amazon, where installed capacity increased from 7 to 43 GW.

The decrease in estimated potential capacity was due not to a decline in Brazil’s hydraulic resources but to a recalculation, after planners eliminated projects that were no longer deemed feasible based on regulatory criteria.

The declining dependence on hydropower in Amazonian countries.Data source: The United Nations – Energy Statistics Database.

This determination followed a 2018 decision by the government to call a halt to future large-scale development of dams in the Amazon, citing the need to reconcile social and environmental impacts with economic criteria and energy demand. This policy was reversed following the election of Jair Bolsonaro, who embraced many of the projects sidelined in 2018 and proposed additional projects that had not been incorporated in the national energy plans.

Current plans are in flux, but the database of proposed hydropower facilities under consideration in the Brazilian Amazon totals 112, with a potential installed capacity of 44 GW. In 2021, Brazil once again runs the risk of experiencing an electricity crisis and, once again, the culprit is lower-than-average water levels in reservoirs.

The nations of the Andes are also highly dependent on hydropower and seek to increase that commitment over the next decade. A recent study documented 142 dams in operation or under construction and an additional 160 in various stages of planning. This is twice the number reported in 2012 and would represent a 500 per cent increase in installed generating capacity.

Hydropower facilities that employ dam-and-tube designs avoid most of the impacts associated with dam-and-reservoir and run-of-river designs. They are used in Bolivia at Zongo/Harpa. Image courtesy of LHUMMS via Flickr (CC BY-SA 2.0).

Peru’s National Energy Plan 2014–2025 projects that 54 per cent of its electricity supply will be generated from hydropower; most will come from dams built in the Ucayali and Marañon basins. Ecuador hopes to increase the proportion of hydroelectric power from 50% in 2015 to approximately 90% by 2025, at least 7% will come from Amazonian basins. Colombia obtains about 65% from hydropower, although none of that is obtained from an Amazonian tributary.

Bolivia has progressively reduced its reliance on hydropower over the last twenty years as it exploited the natural gas fields discovered in the 1990s; however, future plans rely almost exclusively on hydropower. In 2019, the government announced plans for quadrupling the country’s installed capacity, from 1.2 to 5.1 GW, which would increase its reliance on hydropower from thirty to eighty per cent.

In spite of its economic advantages, the physical attributes of the Amazon and its tributaries make hydropower problematic for the conventional dam-and-reservoir (D&R) facilities favored by civil engineers and energy managers. In the lowlands, broad floodplains limit the potential to create reservoirs in confined areas that store large volumes of water; this impedes operators’ ability to regulate reservoir levels for power management. In contrast, the valleys in the Andean foothills provide almost ideal conditions for creating massive reservoirs; however, high sediment loads cause them to lose storage capacity over time, which limits their lifespan as economic assets.

The retention of sediments also impacts ecosystem function in downstream riparian habitats. This is particularly problematic for dams on ‘white-water rivers’ that are ecologically defined by high sediment loads. These rivers, which originate in the Andes, drain only twelve per cent of the basin’s surface, but contribute more than eighty per cent of the sediments that enter the Amazonian floodplain ecosystem.

The proposed construction of multiple dams within the Marañon, Ucayali, Madre de Dios and Madeira basins would have long-term consequences on biogeochemical processes in floodplain habitats along the entire course of the river and eventually would impact the intertidal zones of the delta and the marine ecosystems located above the continental shelf at the mouth of the Amazon.

The distribution of existing and proposed hydropower plants in the Pan Amazon. With exception of about ten large-scale facilities, most existing power plants are located relatively high in individual watersheds.

There are other social and environmental impacts associated with large-scale D&R facilities. Large reservoirs displace rural families, forcing them to abandon villages they have inhabited for decades or even centuries. Many dams are built just below a topographic discontinuity to maximize energy production, but these localities are often inhabited by Indigenous communities that exploit a natural concentration of fish or occupy an essential portage around non-navigable rapids. Reservoirs not only force these families to move but alter the ecosystem function that sustains the local economy above and below the dam.

The day to day operation of a D&R power plant alters the natural habitats located below the dam because managers manipulate water flows to balance the demand for electricity. These are always substantially different from natural flood regimes that regulate the life cycles of species in floodplain habitats. Amazonian rivers are renowned for the movement of fish and other species between the river channel and the backwater habitats, which are defined by the length and depth of seasonal inundation.

Power management disrupts the natural cycles that support wildlife and, consequently, affect the human communities that depend on them. The most obvious impacts occur locally, but alterations to flooding regimes can extend far downstream, while upstream communities suffer impacts when dams block the migration of economically important fish species.

Some impacts are global in scale. Amazonian rainforests are characterised by massive quantities of biomass, and if the standing vegetation is not cleared prior to flooding, the reservoir will generate substantial methane emissions via anaerobic decomposition at the bottom of the reservoir. These emissions can last for decades and nullify any potential savings of greenhouse gases (GHG) associated with hydropower as a renewable energy.

As well as in Bolivia, the concept of hydropower built with a dam and pipeline design has been implemented in some places in Brazil (Dardanelos, Mato Grosso). Image by PAC Collection via Flickr (CC BY-SA 2.0).

One alternative for managing environmental and social impacts is to build dams that employ a run-of-the-river (R-o-R) design that minimizes both the size of the reservoir and sediment removal. These configurations still cause impacts linked to biodiversity loss and the disruption of commercial fisheries. From an engineering perspective, R-o-R hydropower facilities are inefficient because they do not store energy in a large reservoir, which limits operators’ ability to compensate for seasonal variability in water flows. Moreover, the lack of storage capacity exposes the R-o-R facilities and their linked electrical grids to episodic crises caused by drought, a risk that will be significantly greater in future decades due to climate change.

Dam and tunnel (D&T) designs avoid the pitfalls of both D&R and R-o-R configurations by delivering water to a power plant located several hundred metres below the dam. These configurations are popular in mountainous areas because they generate large amounts of energy per cubic metre of water. Their superior efficiency reduces the need for a large reservoir, particularly in geographies characterised by abundant rainfall.

Sediment removal is often close to zero because many D&T combinations are located high in the watershed, where sediment loads are naturally low or because storage times in reservoirs are short. Similarly, their impact on fish populations is minimal because these types of rivers are characterised by waterfalls and rapids that act as natural barriers.

Sediment source in the Amazon Basin (see Wittmann et al., 2010). Courtesy of Hella Wittman-Oelze.

Civil engineers favour large-scale projects because they resolve supply and demand issues over many years and create an infrastructure legacy that appeals to their professional pride. Utility companies prefer them because they conform to their preferred business model of producing energy and commercialising it to urban and industrial centres. Politicians like them because their construction generates tens of thousands of low-skilled jobs. Financial analysts at multilateral institutions approve them because they can allocate significant capital to an industry with guaranteed cash flow that obviates investment risk.

Experience has shown, however, that some projects in the Amazon are just too large or the climatic assumptions that underpin the energy model are inaccurate – or out of date. Unfortunately, corrupt practices have tainted the objectivity of feasibility and environmental studies that are used to evaluate their economic, social and environmental sustainability.

Once hydropower was seen as a sign of progress and embraced by a broad sector of society, but that view has changed in recent decades as environmental and human rights advocates have questioned the sustainability of conventional business models. In advanced economies, there is an emerging consensus that some facilities must be dismantled to restore ecosystem function.

“A Perfect Storm in the Amazon” is a book by Timothy Killeen and contains the author’s viewpoints and analysis. The second edition was published by The White Horse in 2021, under the terms of a Creative Commons license (CC BY 4.0 license).

Read the other excerpted portions of chapter 2 here:

Chapter 2. Infrastructure defines the future

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