Energy Requirements by the Water Sector in the Southwestern US: Past, Present, and Future

Abstract:

Climate, energy, and water are fundamentally linked such that shifts in one sector have cascading impacts on the others. Consideration of the integrated system is necessary to fully understand the individual risk profile of each sector. In defining vulnerabilities and potential adaptations, the policy and regulatory environment must be considered alongside the biological and physical systems. Take, for example, the Southwestern U.S., a naturally arid system, where water availability is declining as a consequence of climate change and population growth. Adaptations by the water sector to convey, store, and develop new water sources (e.g. desalination, groundwater pumping, water-reuse) are strategies designed to enhance sustainability of the sector. But, the energy requirements embedded in these management techniques pose challenges to electric utilities. West wide, approximately 20% of total electricity generation goes toward supplying and heating water. If future investments made by the water sector to deal with changing supply and demand regimes continue to follow current trends, the dependence of water on energy availability will grow, meaning that the water supply will be increasingly reliant on the electricity system. Here, we use the example of long-term aridity and the recent drought in the Western US to illustrate the tradeoffs and challenges inherent at the nexus between energy and water. We present long-term trends in the energy intensity of water supplies in the Southwestern US, with a specific focus on groundwater systems. Projected energy requirements for proposed and future conveyance systems are discussed. The potential impacts of reduced flows on the Colorado River on the energy demands for groundwater pumping in the Lower Colorado River Basin are highlighted.