Impacts of Urban Water Conservation Strategies on Energy, Greenhouse Gas Emissions, and Health: Southern California as a Case Study

Abstract

Objectives: To determine how urban water conservation strategies in California cities can affect water and energy conservation efforts, reduce greenhouse gas emissions, and benefit public health.

Methods: We expanded upon our 2014 health impact assessment of California's urban water conservation strategies by comparing the status quo to 2 options with the greatest potential impact on the interrelated issues of water and energy in California: (1) banning landscape irrigation and (2) expanding alternative water sources (e.g., desalination, recycled water).

Results: Among the water conservation strategies evaluated, expanded use of recycled water stood out as the water conservation strategy with potential to reduce water use, energy use, and greenhouse gas emissions, with relatively small negative impacts for the public's health.

Conclusions: Although the suitability of recycled water for urban uses depends on local climate, geography, current infrastructure, and finances, analyses similar to that presented here can help guide water policy decisions in cities across the globe facing challenges of supplying clean, sustainable water to urban populations.

FIGURE 1—

Energy Intensity of California’s Water Sources ^aFor recycled water systems, energy recovery is not included. For plants that are 10 million gallons per day and larger, the potential energy recovery from biogas is on the order of 115 kWh per acre-foot, potentially offsetting energy needed to treat and distribute water. ^bGroundwater is pumped from differing depths depending on location; this estimate is based on the West Basin Water District in Southern California. ^cThe low value for recycled water is based on West Basin Water District in Southern California whose distribution system uses gravity to deliver the recycled water. ^dGreenhouse gas emissions based on annual average emissions factor for Southern California Edison (0.32 kg carbon dioxide equivalents per kWh) and median energy intensity for each water source.