**The Energy Trade-Offs of Transitioning to a Locally Sourced Water Supply Portfolio in the City of Los Angeles**

#### **Angineh Zohrabian and Kelly T. Sanders \***

Department of Civil and Environmental Engineering, University of Southern California, Los Angeles, CA 90089, USA; azohrabi@usc.edu

**\*** Correspondence: ktsanders@usc.edu

Received: 1 September 2020; Accepted: 9 October 2020; Published: 26 October 2020

**Abstract:** Predicting the energy needs of future water systems is important for coordinating long-term energy and water managemen<sup>t</sup> plans, as both systems are interrelated. We use the case study of the Los Angeles City's Department of Water and Power (LADWP), located in a densely populated, environmentally progressive, and water-poor region, to highlight the trade-offs and tensions that can occur in balancing priorities related to reliable water supply, energy demand for water and greenhouse gas emissions. The city is on its path to achieving higher fractions of local water supplies through the expansion of conservation, water recycling and stormwater capture to replace supply from imported water. We analyze scenarios to simulate a set of future local water supply adoption pathways under average and dry weather conditions, across business as usual and decarbonized grid scenarios. Our results demonstrate that an aggressive local water supply expansion could impact the geospatial distribution of electricity demand for water services, which could place a greater burden on LADWP's electricity system over the next two decades, although the total energy consumed for the utility's water supply might not be significantly changed. A decomposition analysis of the major factors driving electricity demand suggests that in most scenarios, a structural change in LADWP's portfolio of water supply sources affects the electricity demanded for water more than increases in population or water conservation.

**Keywords:** urban water system; local water supply; water-energy nexus; electricity demand; index decomposition analysis
