Assessing Net GHG Emission Reduction - a Scientific Approach for Sustainable Hydropower Development

**Internal World Bank Learning Event**

Presenter: LUC GAGNON, Senior Advisor on Climate Change at Hydro Quebec

Chair: ALESSANDRO PALMIERI, Lead Dam Specialist, Quality Assurance Unit, the World Bank
Discussant: WINSTON YU, Senior Water Resources Specialist, SASDA, the World Bank

Room MC 10-100

Organized by the Combined Water Resources and Watershed Management Thematic Group and OPCQC

Major research programs on GHG emissions from reservoirs started in 1994.  After 16 years of research, we do not have one serious assessment of net emissions. Since 2005, there is a strong consensus that gross emissions measured at the surface of reservoirs, are mainly due to the flushing of carbon to waterways.  Numerous articles discuss and confirm this, notably Cole, Prairie et al. (2007).

The movement of carbon can be summarized by three major fluxes:
  1. The forests temporarily captures large amounts of carbon (primary production). 
  2. Rain and melting snow flushes a very large portion of that carbon, from the forest soils to the rivers, lakes and reservoirs. 
  3. Once in water, much of that carbon is decomposed and returned to the atmosphere.  This cycle explains why forests are often seen as large carbon sinks, while reservoirs are seen as large sources. This is an illusion as, in the long term, the amounts of carbon stored in forests are very small.
After 16 years of research, we have extensive data on fluxes 1 and 3, and not a single measurement on flux no. 2, the flushing of carbon. This information is essential for any realistic modelling of the carbon cycle.

Numerous scientific publications conclude that lakes and reservoirs are large carbon sinks. In many scientific fields, good practice means that two different methods are used to arrive at similar results.  But researchers who have made their career on CO2 flux measurements have rejected such good practice, because the stock method would invalidate their research.
**Internal World Bank Learning Event**