Hydropower plants operate for multiple decades, sometimes even beyond 100 years, and as such are likely to be impacted by climate change during their lifespan. The changes in long‑term climate patterns directly affect hydropower generation. Rising temperatures will likely affect generation output and potential by increasing evaporation losses. Projected water shortage due to melting glaciers along with droughts could affect hydropower generation in regions where hydropower plants rely heavily on glacier water. Changes in precipitation will also alter potential, generation output, peak level and seasonal variations of hydropower. Erratic precipitation patterns could lead to water scarcity and concerns over interrupted hydropower generation. For instance, the electricity supply in Venezuela was interrupted in 2016 and 2018, due to a low water level in hydroelectric dams triggered by a severe droughts. Similarly, Brazil almost entered into electricity rationing when the inflows into the hydropower reservoirs in the Southeast and Northeast regions reached their lowest levels in February 2014 and January 2015 since the records began in 1931.

More frequent extreme weather events such as cyclones or floods and their consequences, such as landslides, can also damage hydropower assets and disrupt electricity supply. For instance, large landslides after heavy precipitation events in 2017 prompted a shutdown of the Callahuanca hydropower plant in Peru.

To analyse climate impacts on Latin American hydropower, this report examined as many combinations of models as possible to enhance the reliability of results. It compared 60 different ensembles of five General Circulation Models (GCM), four Global Hydrological Models (GHM), and three Representative Concentration Pathways (RCP), aiming to minimise the probability of misleading outcomes or distortion by outliers and to ensure diversity. Since outliers are often difficult to avoid due to the complexity of the climate system and the different assumptions within each model, this report compared and aggregated outcomes from various GCMs, GHMs and RCPs, and presented average annual and monthly capacity factors.1

Annual and monthly capacity factors per hydropower plant were mainly derived from a high‑resolution global discharge map (15” × 15”) that combines low-resolution (0.5˚ x 0.5˚) monthly run-off data with high resolution (15” × 15”) area accumulation and drainage direction maps available from HydroSHEDS. These discharge maps were used to extract the design discharge and design load factors per hydropower plant. By placing the discharge of a selected hydropower plant in sequence from the lowest to the highest month of discharge, a flow duration curve was generated. The value of the fourth‑highest discharge month is called the design discharge and determines turbine capacity. The capacity factor is, by design, 100% for the four wettest months and less than 100% for the remaining eight drier months. Further information on the selected models and methodology is described in the Annex.

The assessment shows changes in annual and monthly capacity factors between 2020 and 2099, comparing the projected results with the values of the baseline period from 1970 to 2000. The baseline period was selected reflecting the maximum availability of historical climate records.

The assessment focuses on 13 Latin American countries with the largest installed capacity of hydropower. The selected countries consist of four groups reflecting their climatic characteristics: Central America and Mexico (Mexico, Costa Rica, Panama and Guatemala), Andean region (Colombia, Ecuador and Peru), Southern South America (Argentina and Chile) and the rest of South America (Brazil, Venezuela, Paraguay, and Uruguay).

The total hydropower installed capacity in these 13 countries is over 193 000 MW, which accounts for 98% of total installed capacity in Latin America. Brazil provides over 55% of the total hydropower installed capacity, followed by Venezuela, Mexico, Colombia and Argentina. Given Brazil’s large share of total Latin American hydropower installed capacity, the installed capacity from the 13 countries varies from 9% for Central America and Mexico to 70% for the rest of South America.

This report assesses climate impacts on over 370 hydropower plants, which accounts for 87% of the installed hydropower capacity in 13 Latin American countries. It covers over 168 000 MW, accounting for 86% of the total installed hydropower capacity in Latin America. The selected hydropower plants have various sizes of installed capacity: 20% of them are small hydropower plants with an installed capacity of less than 20 MW, while 62% are 20‑500 MW and 18% are over 500 MW. The assessment calculates climate impacts on each hydropower plant, using each station’s specific geographic coordinates.

This report selected three scenarios and each of them leads to a different global average temperature outcome: Below 2°C, Below 3°C and Above 4°C, respectively by 2100. By comparing these three scenarios, the report aims to present how GHG concentrations are likely to affect hydropower generation in Latin America.

These scenarios are based on the RCP of the Coupled Model Intercomparison Project Phase 5 (CMIP5) of the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report.2 The RCPs show various representative GHG concentration trajectories and their impacts on the future climate (see Annex).

The Below 2°C scenario is based on the projections of the RCP 2.6 that assumes a radiative forcing value of around 2.6 W/m2 in the year 2100. In the Below 2°C scenario, the increase in global annual mean temperature stays below 2 °C by 2100 compared to pre-industrial times (1850‑1900). For the period 2080 to 2100, the global annual mean temperature increases by 1.6 (±0.4) °C above the level of 1850‑1900. The Below 2°C scenario assumes an early peak in global GHG emission trends followed by a drastic decline.

The Below 3°C scenario follows the trajectory of the RCP 4.5 that assumes a radiative forcing value of around 4.5 W/m² in the year 2100. The Below 3°C scenario is associated with a rise by 2.4 (±0.5) °C in global annual mean temperature for the period 2080 to 2100 compared to the pre-industrial level. The Below 3°C scenario assumes a peak in global GHG emission trends by mid-century that subsequently declines.

The Above 4 °C scenario is based on the high-emission trajectory, RCP 8.5, which assumes the absence of additional effort to mitigate GHG emissions. The Above 4°C scenario is associated with a radiative forcing value of around 8.5 W/m² in the year 2100 and a rise by 4.3 (±0.7) °C in global annual mean temperature for the period 2080 to 2100 compared to the pre-industrial level. Under the Above 4°C scenario, global GHG emission does not reach its peak before 2100.

A lack of agreement on future climate and hydrological conditions in certain areas of Latin America sometimes create a gap between the results from various models. Given these embedded limitations, this report aims to examine as many combinations of climate and hydrological models as possible, aggregating various outcomes to present trends on which a majority of models could agree.

The examined sets of models from all three scenarios show that, from now through the end of the century, mean hydropower capacity factor from the assessed plants is projected to decrease due to changing climate conditions. The regional mean capacity factor over the period from 2020 to 2059 is likely to decrease in most of the examined sets of models, by around 8% on average (from 7.5% in the Below 2°C scenario to 9.6% in the Above 4°C scenario), compared to the baseline level from 1970‑2000. The regional mean hydropower capacity factor is projected to be lower than the baseline in the latter 40 years of the century in all examined model sets, although the size of decrease varies among scenarios. Between 2060 and 2099, the regional mean hydropower capacity factor is projected to be lower than the baseline by over 11% on average (from 7.5% in the Below 2°C scenario to 17.4% in the Above 4°C scenario).

The projected decline in hydropower capacity factor could have negative implications to electricity security in Latin America, given the prominence of hydropower as a source for electricity generation. Currently, hydropower accounts for over 50% of electricity generation in Costa Rica, Peru, Brazil, Uruguay and Venezuela, and exceeds 70% in Panama, Ecuador and Paraguay.

A comparison of results from three different GHG concentration scenarios shows that GHG emissions reduction is key to minimise the negative impacts of climate change on Latin American hydropower. The results show that a higher GHG concentration will have stronger negative impacts on hydropower generation in Latin America. In the Above 4°C scenario, which assumes a continuous increase in GHG emissions, there could be a starker decrease in the regional mean hydropower capacity factor for the rest of 21st century than the other scenarios. The hydropower capacity factor is expected to drop by 9% in 2020‑2060 and 17% in 2060‑2100 compared to the baseline level. Conversely, the Below 2°C scenario projects that the regional mean hydropower capacity factor would drop below the baseline level, but then remain stable for the rest of the century.

Although all three scenarios estimate a decline in the regional mean hydropower capacity factor by 2100, this does not mean that climate change will have an equal impact on every hydropower plant. Rather, the impacts of climate change are likely to be spread unevenly across Latin America, exposing some plants to climate change more than others.

The climate projections included in this analysis show that two sub-regions,##3## Central America and Mexico and Southern South America, would see a consistent decrease in mean hydropower capacity factors due to a decline in mean precipitation and runoff. However, the Andean region along the northwest coast of South America is projected to see a slight increase in hydropower capacity factor with increasing precipitation and runoff volume on average. For the rest of South America, a comparatively mild decrease in hydropower capacity factor is expected, although further studies are needed given the low agreement level between climate models for the future conditions of this sub-region. 

Hydropower capacity factor in Central America and Mexico is likely to fall by the end of this century in the Below 3°C and Above 4°C scenarios, mainly due to a consistent decrease in precipitation and runoff. Countries in the northern part of this sub-region, Mexico and Guatemala, are projected to see a starker decrease than Costa Rica and Panama in all scenarios.

Most of the modelling outcomes also show that hydropower capacity factor in Central America and Mexico will react the most sensitively to the increase in GHG emissions than other countries. In the Below 2°C scenario, hydropower capacity factor is estimated to decrease slightly by 5%. However, in the Above 4°C scenario, the mean hydropower capacity factor of Central America and Mexico could drastically fall up to 28%. In Guatemala, where hydropower currently takes up one third of electricity generation, hydropower capacity factor may decline by over 35% compared to the levels of 1970‑2000 in the latter 40 years of this century in the Above 4°C scenario.

A high GHG concentration will raise concerns to Costa Rica and Panama as well. These two countries rely heavily on hydropower that generates over two thirds of their total electricity. Although both countries are expected to maintain a stable level of hydropower capacity factor in the Below 2°C scenario, they will be unable to do so in the Above 4°C scenario. With a high GHG concentration, hydropower capacity factors could fall by 26% and 17% in Costa Rica and Panama respectively. For the electricity security of Costa Rica and Panama, global GHG emissions reduction will be vital.

As climate change is likely to decrease hydropower capacity factors, countries in this sub-region are making efforts to make their hydropower plants more resilient and adapt to changing climate conditions. Mexico announced a new national electricity program in late 2018 to increase hydropower generation capacity by 26% through modernising and upgrading 60 existing hydropower plants. Costa Rica, where almost 100% of electricity is generated from renewable sources—a majority of which is from hydropower, is diversifying its electricity mix by increasing the role of other renewables such as biofuels, geothermal, wind and solar PV. As a result, the share of hydropower in the power mix of Costa Rica has dropped by over 7% during last decade despite the addition of new hydropower capacity such as Reventazón and Bijagua.

Southern South American countries, Chile and Argentina, are projected to experience notable reductions in hydropower generation between 2020 and 2100 in most models. This is largely due to a notable decrease in average precipitation around central Andes and Patagonia, and a reduction in streamflow of major river basins. Southern South America, together with Central America and Mexico, is the region that would show the sharpest drop in hydropower capacity factor.

A majority of modelling outcomes present that hydropower capacity factor of Southern South America is likely to decrease further with higher GHG concentrations. In the Below 2°C scenario, hydropower capacity factor is projected to remain at around 90% of the baseline level for 2020‑2100. In contrast, the Above 4°C scenario projects that hydropower capacity factor is expected to fall by 15% and 28% on average in the periods of 2020‑2060 and 2060‑2100 respectively compared to the baseline; in Chile especially, this decrease is likely to be more marked. If GHG emissions are not mitigated from the level of the Above 4°C scenario, Chile’s hydropower capacity factor could substantially decline by over 34%.

Despite the considerable magnitude of decrease, the projected drop in hydropower capacity factor could have a comparatively mild impact on electricity supply in southern South America. Chile and Argentina are less dependent on hydropower for electricity generation than most of the selected Latin American countries. The hydropower share in electricity generation of Chile was 27% in 2019. In Argentina, where the use of gas to generate electricity has consistently increased, the share of hydropower decreased to 20% in 2019 from 32% in 2000.  

Hydropower generation in the Andean region, including Peru, Ecuador and Colombia, is expected to maintain the baseline level, or even slightly increase by 2100 in a majority of models. This could be due to a notable increase in rainfall along their coastlines, although some locations may experience a mild decrease in precipitation and a decline in runoff with a continuing trend in glacier loss.

Different levels of GHG concentrations are unlikely to have a critical impact on total hydropower generation of the Andean region, where hydropower accounts for the biggest share in electricity generation. Hydropower capacity factors in the Andean region are projected to stay within a range of +3% to -3% from the baseline in all three scenarios. Only in Ecuador a higher GHG concentration may be associated with a mild increase in hydropower capacity factor between 2060‑2100.

Although a changing climate would not have a critical impact on the total hydropower generation in the Andean region, a potential increase in extreme precipitation will likely add stress to hydropower operation. In some areas of the region, climate change is projected to exacerbate seasonal variations, with higher rainfall in the rainy season and less in the dry season with longer periods of drought. The frequency of extreme precipitation events and their consequences, such as floods and droughts, are projected to increase, posing a greater challenge to hydropower plants that do not have seasonal storage capacity. Colombia is expected to see more extreme precipitation events by 26‑37% by 2050. An ENSO phenomenon could also affect hydropower operation, prompting heavy rainfalls and widespread flooding between April and October along the coasts of northern Peru and Ecuador. As that the Andean region relies significantly on hydropower for electricity generation, enhancing their resilience to future extreme precipitation events will be essential for reliable electricity supply and ensuring greater long-term opportunities.

There are still limitations in fully understanding the climate impacts on hydropower capacity factor in the rest of South America. Current climate models often present a marked disparity in forecasting precipitation patterns for this sub-region. For instance, the assessment of various climate models shows a large spread of climate change projections in Brazil. Further studies on future climate patterns across the sub-region would help to obtain more accurate projections.

Despite the limitations, a majority of modelling outcomes show that the mean hydropower capacity factor for the rest of South America (Brazil, Paraguay, Uruguay and Venezuela) for 2020‑2100 would be lower than the level of 1970‑2000. The projections for 2060‑2100 imply a higher GHG concentration would bring a more drastic decline in hydropower capacity factor, although several models present conflicting results about some hydropower plants. A majority of climate models show that the hydropower capacity factor of the rest of South America would decrease by over 15% in 2060‑2100 compared to the baseline (1970‑2000) in the Above 4°C scenario, while it would fall by around 9% in the Below 2°C scenario. 

These modelling outcomes also indicate that national-level trends could vary among countries in each sub-region. For instance, Venezuela is likely to maintain its baseline level of hydropower capacity factor by 2060 in all scenarios, while a majority of the examined models project a decrease for Brazil and Paraguay. Uruguay is projected to have the smallest changes in hydropower capacity factor across three scenarios over the period of 2020‑2100.