Water is consumed in the generation of electricity and then transmitted, virtually, across the electric grid, creating a network of water transfers. Virtual water transfers of electricity are an understudied area of the energy–water nexus, with important policy and conservation considerations. Here we analyse the virtual water flows of the US electric grid and the changes in network structure from 2010 to 2016 using electricity transfers between power control areas and power-plant-level water for electricity. Transfers of blue water were 9.21 km3 in 2010 and 11.21 km3 in 2016. Transfers of grey water were 50.18 km3 in 2010 compared to 71.64 km3 in 2016. The change in blue water transfers are despite national trends of lower freshwater demands of thermoelectric power generation. We provide a mapping of virtual water transfers through the US electric grid over time, including blue and grey water, and network analysis of the system.
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All data utilized within this study are publicly available through the US Energy Information Administration, US Environmental Protection Agency, or the US Federal Energy Regulatory Committee. The Supplementary Information contains datasets generated through the methodology relevant to the analysis and creation of plots. Any other data that support the plots within this paper and other findings of this study are available from the corresponding author upon request.
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C.M.C. was supported by the National Science Foundation Graduate Research Fellowship. L.A.D. received funding from the University of Illinois at Urbana-Champaign Civil and Environmental Engineering Department Fellowship. W.N.L. received funding from the Institute for Sustainability, Energy, and Environment at the University of Illinois at Urbana-Champaign. The authors thank B. Freitag, who helped create the network visualizations.
The authors declare no competing interests.
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Supplementary figures 1–11
Supplementary tables 1–10
This zip file contains the Matlab and R scripts required to perform the analysis presented in this paper. There are four files: computeAnnualStatisticsRevised.m, computeTransferMatrix.m, ComputeGreyWaterFootprints.R, ComputeUncertainties.R. The file computeAnnualStatisticsRevised.m uses the electricity transfer matrices and datasets in Supplementary tables 3–9 to create blue and grey water transfer matrices, network statistics and other relevant data. The file computeTransferMatrix.m uses the dataset in Supplementary table 2 to create a set of matrices of electricity transfers, where one matrix corresponds to a single year of transfers (2010–2016).The file ComputeGreyWaterFootprints.R adds a supplemented value of grey water footprint to United States Energy Information Administration (EIA) form 923 using the methods described in the paper. The script relies on the dataset in Supplementary table 10. It provides the input for computing uncertainties and eventual aggregation of blue and grey water at the principal component analysis (PCA) level. The file ComputeUncertainties.R utilizes the supplemented EIA form 923 from the above R script to determine 25th percentile, median, and 75th percentile values of blue and grey water resources for each thermoelectric power plant. This script uses the methodology described in the main text and computes uncertainty based on all 12 months of the year. These data are used to compute a PCA-level water footprint.
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Chini, C.M., Djehdian, L.A., Lubega, W.N. et al. Virtual water transfers of the US electric grid. Nat Energy 3, 1115–1123 (2018). https://doi.org/10.1038/s41560-018-0266-1