The statistics with which Andrew from California’s Department of Water Resources (DWR) takes issue are from secondary sources, including the Climate Action Plan from his own agency.1 These statistics are cited in the background section of our article and are not used in our analysis. Nonetheless, because the statistics provide a valuable frame for understanding some of the ways in which water conservation can affect the public’s health, and in response to Andrew’s concerns, we have reviewed the most recent primary data sources and have identified three factors contributing to data discrepancies in this area.
First, the percentage of the state’s “total energy” used by the State Water Project (SWP) refers only to electrical energy. The California DWR reports SWP energy usage in terms of electrical energy (watt-hours) used by SWP fixed facilities. Since only electrical energy is included in the numerator of the percentage calculation, the denominator (i.e., the state’s total energy) similarly only includes electrical energy.
Second, some discrepancies are attributable to our use of older, secondary data. The most up-to-date primary data through 2014 (the most recent year available) show that median annual greenhouse gas emissions for the most recent five-year period are 33% to 50% lower than the levels we reported.2,3 Electrical energy usage, however, is still within the range that we reported. Between 2010 and 2014, median annual SWP energy usage4 was 2.8% of the state’s total energy retail electricity sales.5
Third, Andrew cites data from only 2014—a highly atypical year when, in the midst of California’s current drought, SWP water deliveries were only 53% of the median for the preceding five years.6 Correspondingly, energy consumption and greenhouse gas emissions were also unusually low in 2014. SWP water may sometimes be less energy-intensive than alternatives,7 but relevant data must be assessed in a balanced, holistic way.
Although these updated statistics do not impact our analysis or conclusions, we appreciate the opportunity to bring them to the attention of the readership of AJPH.
REFERENCES
- 1.California Department of Water Resources. Climate action plan. Phase 1: greenhouse gas emissions reduction plan. 2012. Available at: http://www.water.ca.gov/climatechange/docs/Final-DWR-ClimateActionPlan.pdf. Accessed November 7, 2016.
- 2.California Department of Water Resources. 2012-2015. Greenhouse Gas Emissions Reduction Plan. Monitoring Report. Available at: http://www.water.ca.gov/climatechange/GHGReports.cfm. Accessed November 7, 2016.
- 3.California Department of Water Resources. 2016. Clean energy for the state water project. Available at: http://www.water.ca.gov/climatechange/docs/2016/CleanEnergyforSWPFinal.5.19.16.pdf. Accessed November 7, 2016.
- 4. California Department of Water Resources. Tables 10-1 (2000-2014): Energy Used at Pumping Plants and Power Plants. Bulletin 132, Management of the State Water Project (01-15).
- 5.US Energy Information Administration. California Electricity Profile (2000-2014). Available at: http://www.eia.gov/electricity/state/California. Accessed November 7, 2016.
- 6. California Department of Water Resources. “Table 9-10: SWP Water Delivered by Category, 1962–2014.” Bulletin 132-15 (2014): Management of the State Water Project.
- 7.Fang AJ, Newell JP, Cousins JJ. The energy and emissions footprint of water supply for Southern California. Environ Res Lett. 2015;10(11):114002. [Google Scholar]