A system model for assessing vehicle use-phase water consumption in urban mobility networks

Water consumption is emerging as an important issue potentially influencing the composition of future urban transportation networks, especially as projected urban populations are expected to outpace water availability and as alternative fuels and vehicles are being implemented in such regions. National and State policies aimed at reducing dependence on imported fuels and energy can increase local production of fuels and energy, impacting demand on local water resources. This article details the development of a model-based assessment on water consumption and withdrawal pertaining to the use-phase of conventional and alternative transportation modes based on regional energy and fuel production. An extensive literature review details water consumption from fuel extraction, processing, and distribution as well as power plant operations. Using Model-Based Systems Engineering principles and the Systems Modeling Language, a multi-level, multi-modal framework was developed and applied to the Metro Atlanta transportation system consisting of conventional and alternative vehicles across varying conditions. According to the analysis, vehicles powered by locally produced biofuels and electricity (assuming average local grid mix for charging) consume more water than locally refined gasoline and CNG-powered vehicles. Improvements in power plant technologies, electricity generation (e.g., use of solar and wind versus hydro power) and vehicle efficiencies can reduce such water consumption significantly. Total water withdrawal for each vehicle and fuel is significantly greater than water consumption.