Environmental and Social Impact Assessment - Gibe III

Gibe III – Environmental and Social Impact Assessment 300 ENV R CS 002 C - A9003099
Measuring Emissions: Net vs. Gross Emissions
One thing that appears extremely important in emissions assessments is to differentiate between net and
gross emissions:
Gross emissions are only those emissions that are measured at the reservoir surface (or from the turbines).
Net emissions take into account the gases emitted from the reservoir as well as the amount of gases that
would have been absorbed by any sinks in the land, and the amount of gases that would have been released
from the land before it was flooded.
The formula for calculating net GHG emissions from a reservoir is:
Net reservoir
emissions
=
Emissions from
reservoir
discharged water
and
+
Pre-dam greenhouse gas sinks
lost due to dam and reservoir
creation
CESI SpA - Mid-Day International Consulting Engineers Page 192
- Pre-dam sources of
greenhouse gas lost
The concept of net emissions relies on knowledge of the ecosystem to be flooded and its role in the carbon
cycle. For example, prior to the creation of a reservoir, the land to be flooded most likely contains both sinks
and sources of GHG’s, including methane and CO2:
• A carbon sink is an area that takes in or “sequesters” more carbon than it releases.