Reducing carbon emissions through water conservation: An analysis of 10 major U.S. cities

Drinking water supply requires energy, which in turn emits greenhouse gases with undesirable climate impacts. Water conservation, therefore, offers environmental benefits by reducing such emissions. This research estimates carbon-dioxide-equivalent (CO2eq) emissions associated with water supply in 10 major U.S. cities by combining existing observations on the energy intensity of water supply and the carbon emissions of energy systems. Results range from 21 to 560 gCO2eq per cubic meter of water delivered. As a pathway for future carbon budgeting, the approach demonstrates how existing water, energy, and emissions data may be combined in studies of multiple sites which are not practical with typical life-cycle analyses. Considering a hypothetical 10% water conservation scenario in each city shows that the potential to reduce emissions (1,200–65,000 tCO2eq/yr in each city) is especially effective where energy-for-water intensities, electricity emission factors, and/or water conservation volumes are high. The results of this and similar analyses may guide future sustainability decisions by considering the co-benefits of reducing energy use and emissions associated with water conservation.