Environmental Effects Studying Net Evaporation from the Eastmain-1 Reservoir A first-of-its-kind study of net evaporation at a hydroelectric facility reveals that the project has very little effect on the loss of water to the atmosphere as compared with pre-impoundment conditions. akes, rivers, wetlands and forests are part of of energy generation are compared adequately in By Alain Tremblay, Simon Lthe Earth’s freshwater cycle. Water and energy terms of the water footprint. Tardif, Ian B. Strachan are intricately linked and are two major necessities This article presents the net water evaporation and Christian Turpin for modern civilizations. As population increases, of a reservoir (Eastmain-1) based on comprehen- the demand for water and energy is growing rap- sive field data. This is a world-first research project idly, creating challenging situations in a context and revealed that the Eastmain-1 reservoir net where freshwater is a scarce resource in many evaporation is close to zero. regions. In the U.S., the energy sector is the largest user of water, accounting for about 50% of the total Site description and methodology water withdrawals yearly.1 The Eastmain-1 Reservoir is in the boreal ecore- Over the past decade, environmental footprints gion of Quebec, Canada, about 800 km north of increasingly have been used to indicate human Montreal. The Eastmain River watershed is domi- impact on the environment,2 with the water foot- nated by coniferous forest and shallow podzolic print receiving much attention. There is an emerg- and peat soils developed over igneous bedrock ing debate about whether hydroelectric generation and quaternary sediments. Aquatic systems are is a significant consumer of water through the described as oligotrophic — characterized by a low evaporation process. Evaporation or evapotranspi- water nutrient concentration, supporting a sparse Alain Tremblay, PhD, is a ration (transfer of moisture from the earth to the growth of algae and other organisms, and having senior environment advisor atmosphere by evaporation of water and transpira- a high oxygen content, with overall low production manager of the greenhouse tion from plants) varies regionally and is affected of algae and fish. gas research program by several parameters — relative air humidity, air The 160-MW Eastmain-1 powerhouse was and Simon Tardif, PhD, is and water temperature, solar radiation, water sur- commissioned in 2006. The main dam and 33 a hydrometeorologist with face area, wind velocity and vegetation type. dikes form the Eastmain-1 Reservoir, with a sur- 2 Hydro-Quebec Production Most data available regarding the water foot- face area of 603 km . Another 768 MW of capacity (Generation). Ian Strachan, print of hydropower complexes only accounts for were added in 2012 with the construction of the PhD, is associate professor gross evaporation estimated using traditional tech- Eastmain-1-A powerhouse, yielding a total energy 2,3 of micrometeorology niques. In many cases, gross evaporation from output from the Eastmain-1 Reservoir of about at McGill University. reservoirs is considered water consumption, and if 6.3 TWh per year (from 2012 forward). As part Christian Turpin, M.Sc., is associated with a water consumption tax, it would of the Eastmain-1-A and Rupert diversion project, an environment advisor increase the hydropower operation cost. Therefore, a portion of the water from the Rupert River was with Hydro-Quebec. an adequate method to evaluate net evaporation diverted to the Eastmain-1 Reservoir. is necessary. Net evaporation is the evaporation The hydrology of the Eastmain-1 Reservoir This article has been evaluated associated with the reservoir minus the evapora- watershed (25,857 km2) reflects the regional cli- and edited in accordance with reviews conducted by two or tion and evapotranspiration that occurred from the mate; runoff is strongly seasonal, with high flows more professionals who have relevant expertise. These peer natural systems before flooding. For governments in the spring (peaking in May or June) and low reviewers judge manuscripts for and the energy sector, the evaluation of net evapo- flows in late winter. The reservoir is covered with technical accuracy, usefulness, and overall importance within ration from hydroelectric reservoirs is becoming ice about 180 days per year. The water discharged the hydroelectric industry. more and more relevant to ensure that methods from Eastmain-1 will flow into the Opinaca Reservoir to be used at the new 138-MW Table 1: Eastmain-1 Monthly Evaporation Sarcelle powerhouse and again at the and Evapotranspiration (in mm of water) 5,616-MW Robert-Bourassa and 1,436- MW La Grande-1 generating stations. 2008 2009 2010 To reduce the impact of the project on EM-1 Forest Peat EM-1 Forest Peat EM-1 Forest Peat the Rupert and Lemare rivers, mitiga- Jan. 6.2 13.6 0.3 1.9 0.9 -0.2 1.0 5.0 0.6 tion measures were put in place. Eight weirs were built on the Rupert River to Feb. 2.5 19.3 1.2 0.8 6.7 0.5 2.4 11.3 2.2 maintain the water level for different Mar. 4.7 18.3 4.9 5.0 15.2 4.2 5.3 9.3 5.9 uses of the river (such as navigation and fish spawning areas), and an ecological Apr. 11.7 17.4 23.9 8.4 29.7 10.8 15.8 16.2 42.3 instream flow that reproduces the mean May 19.5 40.3 52.0 18.0 40.3 30.6 35.7 49.9 76.3 annual natural hydrological cycle on both rivers is maintained. June 38.7 82.8 93.9 32.1 54.3 77.1 77.4 53.4 78.0 Determination of water evaporation July 84.0 99.2 97.7 96.7 61.1 60.5 73.3 89.6 82.5 In an Eastmain-1 Reservoir net green- Aug. 123.4 109.1 83.1 102.0 79.1 54.2 48.9 76.3 70.1 house gas emissions project (www. 4,5 Sept. 124.2 62.7 53.1 74.1 53.7 35.3 71.8 52.5 44.1 eastmain1.org) that was carried out over seven years, many parameters Oct. 93.9 35.3 22.6 98.9 25.4 13.3 62.7 36.3 23.3 were measured, including energy fluxes. Eddy covariance systems were used to Nov. 78.0 18.3 6.9 49.2 21.0 7.4 47.6 16.8 7.2 measure evaporation from the reservoir Dec. 12.7 12.1 1.1 22.6 9.9 1.0 11.4 9.6 1.9 and evapotranspiration from forests and wetlands. The exchange of water vapor Total 599.5 528.5 440.7 509.7 397.3 294.8 453.3 426.1 434.2 measured does not discriminate between evaporation or transpiration. For simplic- ity, the measured water exchange is called while deciduous forest and burned forest March, April, May and December 2008 evapotranspiration, with the understand- respectively represent 16 km2 (5%) and for the peatland site (see Table 1). ing that such exchange from a purely 114 km2 (33%) of the surface area. Wet- The annual regional evapotranspira- aquatic system is evaporation. Details on lands represent 110.9 km2 (18.4%) of the tion budget was calculated as the area- the eddy covariance technique, equations total terrestrial surface.4 weighted sum of the evapotranspiration and calculations are available.6 We used Evapotranspiration was measured over budget for each ecosystem measured. For the standard procedures employed by forest, peatland and the Eastmain-1 Res- lakes and rivers, we used reservoir mean the flux community in applying the eddy ervoir using three eddy covariance towers monthly evaporation values. We did not covariance technique.7 and meteorological stations. Measure- have a long-term representative burned The natural aquatic ecosystem is ments were carried out from June 2006 forest site data set. The types of burns in divided into three categories: rivers, lakes to October 2012 at the forest and reser- the region vary. Burned lowland forested and streams. The Eastmain River rep- voir sites. The eddy covariance tower on sites often had peat substrate and now resents the dominant component in the the peatland site was operated from June resemble peatlands with shrubs and other region, with 82 km2 (55%) of the total 2007 to October 2012. In this study, we vegetated cover. Other lowland burns are aquatic surface area. Up to 827 lakes were used data from January 2008 to Decem- often on shallow mineral soil and, along contained within the flooded lands, with ber 2012 as they represent the most com- with more complete burns, would have areas of 100 m2 to 10 km2, accounting for plete continuous data set. less evapotranspiration. To calculate a 45% of the total aquatic surface. More In certain periods of the year (see burned forest evapotranspiration budget, than 827 streams of various widths and Table 1), daily evaporation or evapo- we consider that 50% of the surface area lengths, from only 10 m up to 5.5 km and transpiration data were unavailable; mean would have similar rates of evapotranspi- totaling 1.3 km2, represent the smallest values of the others years’ data were used ration to the peatland (see Table 1). The component (less than 1%) of the natural to complete certain years. All towers were remaining 50% would be covered by a aquatic system.4 removed in October 2012, consequently lower vegetation density and drier soils, The natural terrestrial ecosystem is monthly values for October, November and we used a lower annual evaporation divided into wetlands and forests.