Changes in scale net greenhouse gas emissions due to land cover changes associated with the creation of reservoirs for the production of hydroelectricity

There are two major sources of greenhouse gas (GHG) emissions due to human activities: direct emissions from the burning of fossil fuels for energy production and indirect emissions resulting from the conversion of land cover types or land-uses that are general sinks and/or stores of carbon. These two sources of CO2 to the atmosphere are approximately 5 to 6, and 1 to 2 Pg C yr-1, respectively. At present, economic growth and energy consumption, the combustion of carbon-based fossil fuels and energy production and population growth in developing and developed economies, and economic growth all are inextricably linked. The consequence is that, for serious reductions in GHGs emissions that will have any significant impact on reducing atmospheric concentration and reducing the estimated extent of future climate change, large non-carbon based forms of energy will be required.

Hydroelectricity can produce much energy and is not based on combustion. Canada still has much potential for increasing this mode of production. Hydroelectricity production in many cases requires the creation of reservoirs that inundate terrestrial ecosystems. It has been reasonably well established that reservoirs emit GHGs but what has not been established is ‘what is the net change in the exchange of GHG that have resulted directly from the creation of the reservoir?' – i.e. ‘what is the net difference between the landscape scale exchange of GHGs before and after reservoir creation, and how does that net difference change over time from when the reservoir was first created to when its reaches a steady-state condition?'. It is this net change that is relevant to the atmospheric concentrations of GHGs, for comparisons among forms of energy production, and the attribution of emissions vis-a-vis C accounting for anthropogenic emissions.

This poster reports on the current status of a new research project aimed at developing a sufficient scientific understanding of the problem to produce a scientifically creditable estimate of the effect of a Canadian reservoir on the net emission of GHGs. The project personnel bring together expertise in GHG flux measurements, modelling ecosystem carbon dynamics, remote sensing of land cover change, and paleoecological characterization of ecosystems to: 1. compare the continuous exchange of CO2, obtained by eddy covariance (EC) techniques, from the surface of a reservoir and adjacent terrestrial ecosystems that are representative of the major cover types flooded by the reservoir; 2. compare within the footprint of the EC tower on the reservoir the fluxes obtained by EC with those measured by several other techniques typically used in reservoir GHG exchange studies; and 3. adapt existing ecosystem models to simulate the inter-annual net ecosystem exchange for the land cover types that are being flooded by the reservoir and compare the simulated NEE with the exchanges measured from the reservoir and projected from measurements on older reservoirs to obtain a first-order estimate of the net change in GHG exchange due to reservoir creation and maintenance in the present climate conditions and with potential climate change.

This project will provide: 1) the first measurement of CO2 between a new reservoir and the atmosphere as the reservoir is being created; 2) a rigorous intercomparison of the standard methods of determining atmospheric-reservoir exchanges and the EC approach; and 3) the development of the methodology and the first attempt of approaching the issue of GHGs emissions from northern hydroelectric reservoirs as a land cover change. Therefore we will provide an estimate of what the change in GHG source the atmosphere would see, an estimate of the net emissions that can be used for intercomparison of GHG contributions with other modes of power production and a basis on which to develop biogeochemical sound, verifiable, and transparent estimates for GHG accounting.