Carbon capture and sequestration (CCS) has important implications relative to future thermoelectric water use. A bounding analysis is performed using past greenhouse gas emission policy proposals and assumes either all effected capacity retires (lower water use bound) or is retrofitted (upper bound). The analysis is performed in the context of recent trends in electric power generation expansion, namely high penetration of natural gas and renewables along with constrained cooling system options. Results indicate thermoelectric freshwater withdrawals nationwide could increase by roughly 1% or decrease by up to 60% relative to 2009 levels, while consumption could increase as much as 21% or decrease as much as 28%. To identify where changes in freshwater use might be problematic at a regional level, electric power production has been mapped onto watersheds with limited water availability (where consumption exceeds 70% of gauged streamflow). Results suggest that between 0.44 and 0.96 Mm(3)/d of new thermoelectric freshwater consumption could occur in watersheds with limited water availability, while power plant retirements in these watersheds could yield 0.90 to 1.0 Mm(3)/d of water savings.

System dynamics, Complex systems, Collaborative modeling, Public participation, Interdisciplinary,

No abstract

Abstract. Hydrologic processes in the semiarid regions of the Southwest United States are considered to be highly susceptible to variations in temperature and precipitation characteristics due to the effects of climate change. Relatively little is known about the potential impacts of climate change on the basin hydrologic response, namely streamflow, evapotranspiration and recharge, in the region. In this study, we present the development and application of a continuous, semi-distributed watershed model for climate change studies in semiarid basins of the Southwest US. Our objective is to capture hydrologic processes in large watersheds, while accounting for the spatial and temporal variations of climate forcing and basin properties in a simple fashion. We apply the model to the Río Salado basin in central New Mexico since it exhibits both a winter and summer precipitation regime and has a historical streamflow record for model testing purposes. Subsequently, we use a sequence of climate change scenarios that capture observed trends for winter and summer precipitation, as well as their interaction with higher temperatures, to perform long-term ensemble simulations of the basin response. Results of the modeling exercise indicate that precipitation uncertainty is amplified in the hydrologic response, in particular for processes that depend on a soil saturation threshold. We obtained substantially different hydrologic sensitivities for winter and summer precipitation ensembles, indicating a greater sensitivity to more intense summer storms as compared to more frequent winter events. In addition, the impact of changes in precipitation characterisCorrespondence to: E. R. Vivoni (vivoni@asu.edu) tics overwhelmed the effects of increased temperature in the study basin. Nevertheless, combined trends in precipitation and temperature yield a more sensitive hydrologic response throughout the year.

Supporting pre-production software is no easy task, yet their model proved to be a crucial component of the regional water stress analysis. We would also like to thank Erik Schuster and his team at the National Energy Technology Laboratory for compiling much of the data that went into the Sandia model. Darlene Steward and Mark Ruth of the National Renewable Energy Laboratory have been important partners in tying this analysis to the existing frameworks of H2A and the MSM. Executive Summary Water is a key feedstock to the hydrogen production process. Water is a process input (some, if not all hydrogen will come from the H 2 in H 2 O), and at least as importantly, water is used to cool the process equipment that will make hydrogen. Water is also an input to other lifecycle steps, particularly the generation of electricity. Water is abundant. Even in areas expected to achieve high levels of hydrogen vehicle market penetration, water use for hydrogen production is unlikely to be more than 1.5% of the local freshwater supply. Other uses of water such as agriculture and power production make hydrogen's anticipated use appear trivial. Water is inexpensive. Under reasonable economic assumptions, the cost of purchasing water, water treatment (including capital costs) and disposing of wastewater is expected to comprise less than $0.09 per kg hydrogen. However, it is still important for stakeholders in the hydrogen industry to understand the engineering, economic, environmental and policy issues related to water. In particular, this report addresses two key areas: Technology Options There are two widely available options for water treatment: reverse osmosis and ion exchange. Similarly, there are two classes of process cooling: cooling towers and dry cooling. In general, these technologies face tradeoffs in cost, power consumption, total water input ("withdrawal") and wastewater generation ("discharge"). This report identifies the water purchase and discharge costs at which it makes sense to transition from a low-cost, high-withdrawal technology to a high-cost, low-withdrawal technology. Water Resources In order to anticipate the need for different water strategies, the stress on water resources and state of water prices in localities of interest to the hydrogen industry were analyzed. It was found that water purchase and disposal prices are not high enough anywhere to be a factor in early-stage hydrogen deployment, but that many locations exhibit risk factors (higher-than-average prices, low industrial water use, or high water stress) that warrant special attention. 1. Introduction The multi-year program plan for the Department of Energy's Hydrogen and Fuel Cells Technology Program (USDOE, 2007a) calls for the development of system models to determine economic, environmental and cross-cutting impacts of the transition to a hydrogen economy. One component of the hydrogen production and delivery chain is water; water's use and disposal can incur costs and environmental consequences for almost any industrial product. It has b...