Research papersDoes the creation of a boreal hydroelectric reservoir result in a net change in evaporation?

- The net change in evaporation from the creation of a boreal hydro reservoir was studied.
- Eddy covariance towers over four ecosystems evaluated the water flux for five years.
- Reservoir creation led to increased evaporation because of a shift in the timing of emissions.
- The net change in evaporation was dependent on management and less on differences in weather conditions.

Estimates of water consumption from hydroelectricity production are hampered by a lack of common methodological approaches. Studies typically use gross evaporation estimates which do not take into account the evaporative water loss from the pre-flooded ecosystems that would occur without the presence of a reservoir. We evaluate the net change in evaporation following the creation of a hydroelectric reservoir located in the Canadian boreal region. We use a direct measurement technique (eddy covariance) over four different ecosystems to evaluate the pre- and post-flood landscape water flux over a five-year period. The net effect of reservoir creation was to increase evaporation over that of the pre-flooded ecosystem. This change was dependent both on management and differences in the timing of the evaporation with nighttime and autumn contributing strongly to the reservoir evaporation. Managed reduction of water level, and thus the evaporating area, reduced the evaporation.