International Rivers' Comments on Proposed CDM Methodology for Bumbuna Hydro (Sierra Leone)

Thursday, July 14, 2005
Submitted to CDM Methodology Panel

Title of new baseline methodology: Hydropower Projects that Create New Reservoirs or Expand Existing Ones (NM0121)

The methodology is commendable in that it is the first one to recognize the need to measure emissions of CO2 and CH4 emissions from reservoirs (including degassing at the dam outlets).

An important weakness of the proposed methodology is that it does not appear to allow for independent third–party experts to carry out the recommended measurements. It appears that project developers/operators would themselves carry out the measurements. This sets up an unacceptable conflict of interest. The verification body would have no way of knowing if the records of emission values were accurate. Reservoir emissions could potentially reduce the number of CERs earned from a project to zero so the elimination of even the perception of a conflict of interest in their measurement is essential.

Another weakness is that the methodology does not attempt to measure pre–dam sources and sinks which would enable an estimate of net, rather than gross emissions to be made. A final weakness is that the methodology does not allow for the measurement of pre– and post–dam fluxes of nitrous oxide. Although few studies have been done on N20 fluxes from reservoirs recent evidence from Brazil shows that N20 fluxes can represent a significant proportion of the total climate impact of a reservoir. The climate impact of the net N20 emissions at Serra da Mesa reservoir (measured in March 2004) were 64% of the impact from its net methane emissions. (see Elizabeth Sikar et al. 2005)

Any changes needed to improve the methodology:

Major changes: Include assessment of pre–dam sources and sinks in the reservoir zone so that net rather than gross emissions can be measured. Include measurements of net N20 emissions as well as CO2 and CH4. Insist that all measurements and analysis of reservoir fluxes be done by third–party bodies with no interest in the outcome of their work.

Patrick McCully
International Rivers
July 14, 2005