Exploring the Water-Energy Nexus in California via an Integrative Modeling Approach
A comprehensive model of Southwestern U.S. was developed within the Water Evaluation and Planning (WEAP) model. The novelty of the model is that it is driven by monthly climate data, where snowmelt and rainfall-runoff processes generate streamflow, which is routed through both the natural and managed water system network to be stored in reservoirs for future water use and hydropower generation, delivered to end-use demands and meet environmental targets. The work describes the potential impact of climate variability and change on water delivery and end use, including hydropower and inter-basin transfers.
Water is heavy, and the western U.S., is one of the biggest consumers of electric energy, as treating and distributing water for both municipal and agricultural uses is energy-intensive. Hydropower generation is also an important part of the U.S. strategy toward a carbon-neutral energy future. Developing modeling frameworks that can be used to explore the interactions of climate, hydrology, water management, and energy is critically important to better manage these resources across the western U.S.
A climatically driven water system modeling was developed within the Water Evaluation and Planning (WEAP) system for the Southwestern United States, which includes a detailed representation of California’s water supply and demand network. The model allows for the exploration of water-energy interactions through the evaluation of the regional water balances, including metrics of water supply, water use, groundwater storage, environmental requirements, hydropower generation, and the energy use associated with managing water. The ability of the model to address policy-relevant questions was demonstrated by evaluating the impacts of a 30-year drought scenario that included a 2°C warming trend through 2050. With drought, the total energy used to supply water decreases by about 3% compared to the historic use, and warming alone reduces overall energy use by a modest 1% due to overall reductions in water delivery. However, groundwater use increases, with overall groundwater overdraft decreasing storage by almost 10%, with a corresponding increase in energy use.