Methodology of the climate impact assessment


This report assessed the climate impacts on the hydropower plants in 13 Latin American countries between 2020 and 2100, comparing the 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 (IHA, 2020). Brazil takes up over 55% of the total hydropower installed capacity, followed by Venezuela, Mexico, Colombia and Argentina.

Around 90% of selected hydropower plants are impoundment facilities with reservoirs. Around 10% of selected plants are mostly diversion (run-of-river) facilities with a small fraction of pumped hydropower storage. Each hydropower plant assessed in the study has a different level of capacity factors during the baseline period, depending on its location, size, type and other conditions. To present an integrated analysis of climate impacts on different hydropower plants, the study uses only relative values (% of changes compared to the baseline).

Share of selected hydropower plants in terms of hydropower installed capacity, by country


Number of selected plants

Installed capacity of

selected plants [MW]

Total installed capacity [MW]**




9 903

11 310




92 398

109 058




6 075

6 739




10 422

11 918


Costa Rica


2 014

2 343




4 039

5 074




1 321

1 559




10 959

12 126




1 434

1 786




8 810

8 810




4 370

5 396




1 538

1 538




15 049

15 393




168 331

193 050


* The number is calculated by aggregating the number of selected plants per each country and subtracting the number of plants under co-ownership between two countries to avoid double counting. * * Source: International Hydropower Association (2020), 2020 Hydropower Status Report.

Models and data

High-resolution (15’’x 15’’) global monthly discharge maps are developed by combining low-resolution (0.5˚x 0.5˚) monthly runoff data from each ensemble of General Circulation Models (GCM), Global Hydrological Models (GHM) and Representative Concentration Pathways (RCP) with high-resolution (15’’x 15’’) area accumulation and drainage direction maps available from the HydroSHEDS project (ISIMIP, Database; Gernaat et al., 2017; Lehner et al., 2008), and a low-resolution (0.5˚ x 0.5˚) map of monthly runoff.

The discharge maps were used to extract the design discharge and design load factors per hydropower plant (Gernaat, 2019). By ordering the discharge of a selected hydropower plant 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.

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 GCMs, four GHMs, and three RCPs to minimise the probability of misleading outcome and distortion by outliers. 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. Further studies using downscaled GCMs to regional or local levels and then combining GHMs could advance the accuracy of results (Maceira, M.E.P. et al., 2018).

Overview of the GCMs, GHMs and RCPs considered in the assessment

General Circulation Models (GCM)

Global Hydrological Models (GHM)

Representative Concentration Pathways (RCP)



RCP 2.6



RCP 4.5



RCP 8.5







General Circulation Models (GCM)

GFDL-ESM2M was developed by scientists at the Geophysical Fluid Dynamics Laboratory to make projections of the behaviour of the atmosphere, the oceans and climate, using super-computer and data storage resources. The Laboratory has contributed to each assessment of the IPCC since 1990.

HadGEM2 stands for the Hadley Centre Global Environment Model version 2. The HadGEM2 family of models includes a coupled atmosphere-ocean configuration, with or without a vertical extension in the atmosphere to include a well-resolved stratosphere, and an Earth-System configuration which includes dynamic vegetation, ocean biology and atmospheric chemistry. Members of the HadGEM2 family were used in the IPCC Fifth Assessment Report.

IPSL-CM5 model is a full earth system model and the last version of the Institut Pierre Simon Laplace (IPSL) that is a consortium of nine research laboratories on climate and the global environment. Based on a physical atmosphere-land-ocean-sea ice model, it also includes a representation of the carbon cycle, the stratospheric chemistry and the tropospheric chemistry with aerosols. The IPSL-CM5 model contributed to the modelling for the IPCC Fifth Assessment Report.

MIROC-ESM was developed by the Japan Agency for Marine-Earth Science and Technology, Atmosphere and Ocean Research Institute (The University of Tokyo), and National Institute for Environmental Studies.

NorESM1 is the first version of the Norwegian earth system model. It has been applied with medium spatial resolution to provide results for the modelling for IPCC Fifth Assessment Report. It provides complementary results to the evaluation of possible anthropogenic climate change.

Global Hydrological Models (GHM)

H08 is a grid-cell based global hydrological model developed by the National Institute for Environmental Studies of Japan. It consists of six sub-models, namely land surface hydrology, river routing, reservoir operation, crop growth, environmental flow and water abstraction.

LPJmL is a dynamic global vegetation model with managed land use and river routing. It is managed by the Potsdam Institute for Climate Impact Research. It is designed to simulate vegetation composition and distribution as well as stocks and land-atmosphere exchange flows of carbon and water, for both natural and agricultural ecosystems.

MPI-HM is a global hydrological model developed by the Max Planck Institute to investigate hydrological research questions mostly related to high resolution river routing. While hydrological processes are implemented in similar complexity as in full land surface models, the MPI-HM does not compute any energy-related fluxes.

PCR-GLOBWB is a grid-based global hydrology and water resources model developed at Utrecht University. The computational grid covers all continents except Greenland and Antarctica. It simulates moisture storage in two vertically stacked upper soil layers, as well as the water exchange between the soil, the atmosphere and the underlying groundwater reservoir. The exchange with the atmosphere comprises precipitation, evaporation from soils, open water, snow and soils and plant transpiration, while the model also simulates snow accumulation, snowmelt and glacier melt. 

Representative Concentration Pathways (RCP)

The IPCC Fifth Assessment Report defines RCPs as scenarios that include time series of emissions and concentrations of the full suite of GHGs and aerosols and chemically active gases, as well as land use/land cover (Moss et al., 2008). The word representative signifies that each RCP provides only one of many possible scenarios that leads to the specific radiative forcing characteristics. In the IPCC Fifth Assessment Report, four RCPs are presented: RCP 2.6, RCP 4.5, RCP 6.0 and RCP 8.5. The RCPs show various representative GHG concentration trajectories and the impact of each level of GHG concentration on the future climate.

In the forthcoming IPCC Sixth Assessment Report will use Shared Socioeconomic Pathways (SSPs) which show how societal choices will affect GHG emissions and how the climate goals of the Paris Agreement could be met. SSPs are expected to fill the missing piece of socioeconomic narratives in RCPs, looking at five different ways in which the world might evolve in the absence of climate policy and how different levels of climate change mitigation could be achieved when the mitigation targets of RCPs are combined with the SSPs. Although this report decided to use RCPs instead of SSPs, given that still more data resources are available for RCPs rather than SSPs across various GCMs and GHMs. This impact assessment could be updated soon reflecting the new trajectories of SSPs.

This report developed three scenarios based on three different RCPs. Each of them leads to a different global average temperature outcome: Below 2°C, Below 3°C and Above 4°C, respectively. By comparing these three scenarios, the report aims to present how greenhouse gas (GHG) concentrations are likely to affect hydropower generation in Latin America.

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. Under the Below 2°C scenario the rise 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 which 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 and a subsequent decline.

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.

Overview of the scenarios


Below 2°C

Below 3°C

Above 4°C

Representative Concentration Pathway

RCP 2.6

RCP 4.5

RCP 8.5

Targeted radiative forcing in the year 2100

2.6 W/m2

4.5 W/m2

8.5 W/m2

CO2-equivalent concentrations (ppm)




Global temperature change

1.6 (±0.4)°C

2.4 (±0.5)°C

4.3 (±0.7)°C

Likelihood of staying below a specific temperature level over the 21st century

Likely to stay below 2°C

Likely to stay below 3°C

More unlikely than likely to stay below 4°C

Source: IPCC (2014), Climate Change 2014 Synthesis Report,


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