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Key assumptions and how the HydroCalculator works

The tool calculates the net present value (NPV - definition and explanation) on a hydroelectric dam investment based on costs and benefits over a 50-year period. Many dams last longer than that, but their NPV is not significantly influenced by cash flows in the distant future. The tool assumes that dams begin operation in the first year after construction is complete. Annual operation and maintenance costs are calculated as 4% of construction costs and there are no significant reinvestment costs included once the dam is operational. Future costs and benefits are discounted at an economic discount rate entered by users.

In this first release of the model, financial and economic prices are assumed to be the same. In other words the financial to economic conversion factors are assumed to be equal to 1. This simplification may bias results substantially if either the prices of inputs or the price of energy is distorted. Future releases will have more precise conversion factors. User suggestions on reliable and country-specific sources for conversion factors are welcome.

The tool calculates carbon dioxide emissions based on global average carbon content for different vegetation types. A value of US$5 per ton CO2e is used for all countries. Carbon dioxide equivalent is calculated using the Biome Carbon Loss model, which considers methane and carbon dioxide emissions from the reservoir's surface. It does not include emissions of methane "gasified" when methane hits turbines and downstream structures. These emissions can be 50% or more of the total but are omitted in the HydroCalculator due to their extreme variability. The model calculates net emissions, equal to the dam's emissions minus greenhouse gases from alternative sources of an equivalent amount of electricity. These sources represent the short-term mix of sources in each of the countries for which we have information. Net emissions can be negative for dams with large powerplants relative to their reservoir size and/or sparse vegetation covering the flooded land. Negative net emissions are also more likely where the alternative source of electricity is a plant burning fossil fuels.

The people displaced and land area flooded per MW is a simple ratio of the user-provided values. More detailed accounting of environmental and social costs is beyond the scope of the model.

Read an abstract of a speech about environmental impacts of hydroelectric dams in the Amazon.
Read an article titled Unlearned Lessons for Hydroelectric Development in Amazonia.

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HydroCalculator Input Methodology

As noted, the HydroCalculator calculates net greenhouse gas emissions, equal to the dam's emissions minus greenhouse gases from alternative sources of an equivalent amount of electricity (sources of electricity other than the dam in question). Central to this calculation is a parameter describing the magnitude of greenhouse gas emissions produced for every MWh of electricity generated from these alternative sources (tCO2e/MWh). This statistic varies by country and over time, as electricity generation mixes change, altering the relative environmental effects of adding hydropower.

General Procedure For Finding a Country's tCO2e/MWh Value:

-Find the country’s electricity generation mix for the year in question, the magnitude of each source’s annual production in MWh/year.
-Find the emission factors for the country’s electricity generation sources in TCO2e/MWh. If country-specific emissions factors are not available, use regional emission factors.
-Multiply the previous two numbers to obtain TCO2e/year (the year in question). Sum the values obtained for each production source.
-Divide total TCO2e/year (just found) by country’s total electric production for that year to get the weighted average of the country’s electricity production emissions in TCO2/MWh.

General Sources Used in Calculating This Statistic:

IEA Energy Statistics Database

CIA “World Factbook”

UN Energy Statistics Database

Emissions Factors (Coal, Oil, and Natural Gas)

Emissions Factor (Geothermal)

Bases for Individual Countries' Current/Projected tCO2e/MWh In the Coming Decades:

AFRICA

Burundi:
• Energy mix was found from UN Energy Statistics database and CIA World Factbook. Most current year on record was 2010.
• Because of lack of data on individual fossil fuel shares, an emissions factor found by averaging coal, oil, and gas values was applied to the known total thermal production value in order to get TCO2e/year from thermal production sources. Used continental emissions factor values (2008-2010 averages) found in IEA’s CO2 Emissions Fuel Combustion Highlights (2012).

Central African Republic:
• Energy mix was found from UN Energy Statistics database and CIA World Factbook. Most current year on record was 2010.
• Because of lack of data on individual fossil fuel shares, an emissions factor found by averaging coal, oil, and gas values was applied to the known total thermal production value in order to get TCO2e/year from thermal production sources. Used continental emissions factor values (2008-2010 averages) found in IEA’s CO2 Emissions Fuel Combustion Highlights (2012).

Democratic Republic of Congo:
• 2010 emissions factor (all production sources) was found in IEA’s CO2 Emissions Fuel Combustion Highlights (2012).

Ethiopia:
• 2010 emissions factor (all production sources) was found in IEA’s CO2 Emissions Fuel Combustion Highlights (2012).

Ghana:
• Energy mix was found from UN Energy Statistics database and CIA World Factbook. Most current year on record was 2010.
• Because of lack of data on individual fossil fuel shares, an emissions factor found by averaging coal, oil, and gas values was applied to the known total thermal production value in order to get TCO2e/year from thermal production sources. Used Ghana-specific emissions factor for oil (2008-2010 average) and continental emissions factors for coal/peat and natural gas (2008-2010 averages), all found in IEA’s CO2 Emissions Fuel Combustion Highlights (2012).

Guinea (Conakry):
• Energy mix was found from UN Energy Statistics database and CIA World Factbook. Most current year on record was 2010.
• Because of lack of data on individual fossil fuel shares, an emissions factor found by averaging coal, oil, and gas values was applied to the known total thermal production value in order to get TCO2e/year from thermal production sources. Used continental emissions factor values (2008-2010 averages) found in IEA’s CO2 Emissions Fuel Combustion Highlights (2012).

Kenya:
• Current energy mix was found from IEA energy statistics database.
• Used Kenya-specific oil emissions factor found in IEA’s CO2 Emissions Fuel Combustion Highlights (2012) and general geothermal emissions factor.

Lesotho:
• Energy mix was found from UN Energy Statistics database and CIA World Factbook. Most current year on record was 2010.
• Because all electricity production came from hydro in 2010, an emissions factor of 0 was assumed.

Mali:
• Energy mix was found from UN Energy Statistics database and CIA World Factbook. Most current year on record was 2010.
• Because of lack of data on individual fossil fuel shares, an emissions factor found by averaging coal, oil, and gas values was applied to the known total thermal production value in order to get TCO2e/year from thermal production sources. Used continental emissions factor values (2008-2010 averages) found in IEA’s CO2 Emissions Fuel Combustion Highlights (2012).

Mozambique:
• 2010 emissions factor (all production sources) was found in IEA’s CO2 Emissions Fuel Combustion Highlights (2012).

Rwanda:
• Energy mix was found from UN Energy Statistics database and CIA World Factbook. Most current year on record was 2010.
• Because of lack of data on individual fossil fuel shares, an emissions factor found by averaging coal, oil, and gas values was applied to the known total thermal production value in order to get TCO2e/year from thermal production sources. Used continental emissions factor values (2008-2010 averages) found in IEA’s CO2 Emissions Fuel Combustion Highlights (2012).

Senegal:
• Energy mix was found from UN Energy Statistics database and CIA World Factbook. Most current year on record was 2010.
• Because of lack of data on individual fossil fuel shares, an emissions factor found by averaging coal, oil, and gas values was applied to the known total thermal production value in order to get TCO2e/year from thermal production sources. Used Ghana-specific emissions factors for oil and natural gas (2008-2010 averages) and continental emissions factors for coal/peat (2008-2010 average), all found in IEA’s CO2 Emissions Fuel Combustion Highlights (2012).

Sudan:
• Current energy mix was found from IEA energy statistics database.
• Used Sudan-specific emissions factor for oil.

Tanzania:
• Energy mix was found from US Energy Information Administration (EIA) database and CIA World Factbook. Most current year on record was 2010.
• Because of lack of data on individual fossil fuel shares, an emissions factor found by averaging coal, oil, and gas values was applied to the known total thermal production value in order to get TCO2e/year from thermal production sources. Used continental emissions factor values (2008-2010 averages) found in IEA’s CO2 Emissions Fuel Combustion Highlights (2012).

Uganda:
• Current energy mix was found from IEA energy statistics database.
• Used continental emissions factor values (2008-2010 averages) found in IEA’s CO2 Emissions Fuel Combustion Highlights (2012) and general geothermal emissions factor.

Zambia:
• 2010 emissions factor (all production sources) was found in IEA’s CO2 Emissions Fuel Combustion Highlights (2012).

Zimbabwe:
• 2010 emissions factor (all production sources) was found in IEA’s CO2 Emissions Fuel Combustion Highlights (2012).

LATIN AMERICA

Argentina
• Current energy mix was found from IEA energy statistics database.
• Used Argentina-specific emissions factors.

Chile
• Current energy mix was found from IEA energy statistics database.
• Used Latin America emissions factors.

Costa Rica
• Current energy mix was found from IEA energy statistics database.
• Used Costa Rica-specific emissions factors for oil, Latin America emissions factors for coal and gas, and general emissions factor for geothermal.

Guatemala
• Current energy mix was found from IEA energy statistics database.
• Used Guatemala-specific emissions factors.

Honduras
• Current energy mix was found from IEA energy statistics database.
• Used Honduras-specific (oil) emissions factor.

Mexico
• Current energy mix was found from IEA energy statistics database.
• Used Mexico-specific emissions factors for thermal production and general geothermal emissions factor.

Nicaragua
• Current energy mix was found from IEA energy statistics database.
• Used Nicaragua-specific (oil) emissions factor and general geothermal emissions factor.

Panama
• Current energy mix was found from IEA energy statistics database.
• Used Panama-specific (oil) emissions factor.

ASIA

Bhutan
• Current energy mix was found using electricity generating source percentages (Overview of Energy Policies of Bhutan-pdf) and total production data from CIA economic statistics database.
• Used continental Asia emissions factors.

Cambodia
• Current energy mix was found form IEA energy statistics database.
• Used Cambodia-specific (oil) emissions factor.

China
• Current energy mix was found from IEA energy statistics database.
• Used China-specific emissions factors for thermal production and general geothermal emissions factor.

India
• Current energy mix was found from IEA energy statistics database.
• Used India-specific emissions factors.

Laos
• Current energy mix was found from CIA economy statistics database.
• Because of lack of data on the specific composition of thermal production, an averaged thermal emissions factor was applied to the known total thermal production value in order to get TCO2e/year from thermal.

Nepal
• Current energy mix was found from IEA energy statistics database.
• Used Nepal-specific (oil) emissions factor.

Pakistan
• Current energy mix was found from IEA energy statistics database.
• Used Pakistan-specific emissions factors.

Thailand
• Current energy mix found from IEA energy statistics database.
• Used Thailand-specific emissions factors for thermal production and general geothermal emissions factor.

Vietnam
• Current energy mix was found from IEA energy statistics database.
• Used Vietnam-specific emissions factors.