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Extreme heat events are the deadliest weather-related event in the United States. Cities throughout the United States have worked to develop heat adaptation strategies to limit the impact of extreme heat on vulnerable populations. However, the COVID-19 pandemic presented unprecedented challenges to local governments. This paper provides a preliminary review of strategies and interventions used to manage compound COVID-19-extreme heat events in the 25 most populous cities of the United States. Heat adaptation strategies employed prior to the COVID-19 pandemic were not adequate to meet during the co-occurring compound hazard of COVID-19-EHE. Long-term climate-adaptation strategies will require leveraging physical, financial, and community resources across multiple city departments to meet the needs of compound hazards, such as COVID-19 and extreme heat.

Infrastructure are at the center of three trends: accelerating human activities, increasing uncertainty in social, technological, and climatological factors, and increasing complexity of the systems themselves and environments in which they operate. Resilience theory can help infrastructure managers navigate increasing complexity. Engineering framings of resilience will need to evolve beyond robustness to consider adaptation and transformation, and the ability to handle surprise. Agility and flexibility in both physical assets and governance will need to be emphasized, and sensemaking capabilities will need to be reoriented. Transforming infrastructure is necessary to ensuring that core systems keep pace with a changing world.

Predicting the energy needs of future water systems is important for coordinating long-term energy and water management 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.

The value of water use quantification assessments is hindered by the use of inconsistent terminology and reporting standards. Challenges associated with data collection and maintenance are ...

Prior studies conclude that climate plays one of the most important roles in driving variations in residential electricity consumption. While some past studies have quantified sensitivities of electricity use to ambient temperature, 1) few previous studies utilize both high temporal and spatial resolution electricity data, and 2) no research to our knowledge has investigated how the temporal and spatial resolution of electricity data, and choice of ambient temperature indicators, affects quantification of these sensitivities. In this study, we use smart meter data records of electricity use for 1245 households across California, along with hourly ambient temperature records, to compute electricity–temperature sensitivities using a segmented linear regression approach. We find that electricity use and temperature show the strongest relationships when computed using daily accumulated electricity use and daily average temperatures; using these metrics results in a mean electricity–temperature sensitivity of 0.11 kW °C−1. This value is higher than corresponding sensitivities computed using spatially aggregated data, with values ranging from 0.097–0.10 kW °C−1 depending on the amount of spatial aggregation. Through presenting probability density functions of household-level electricity–temperature sensitivities, we illustrate insights that can be gleaned using high resolution electricity datasets such as that used here. We note that values of electricity–temperature sensitivity reported here are representative of the 1245 households under investigation.

This study investigates how technological transitions across California's power sector have shifted its state-level carbon dioxide emissions and cooling water consumption intensities. Its ultimate goal is to evaluate how the state's climate mitigation and environmental policies have affected the power sector's vulnerability to extreme drought and how extreme drought has affected progress towards the state's climate mitigation priorities. The study analyzes the period spanning 2010–2016, which includes one of the state's most severe droughts on record. The results indicate that the growth of variable renewable energy generation has helped offset some of the negative consequences of drought, which include increased emissions and cooling water usage by natural gas generators during periods of low hydropower. However, the retirement of the San Onofre nuclear power plant has delayed the overall decarbonization of the state's power sector, and the closure of significant coastal power plant capacity could increase the freshwater consumption of the power sector if replacement capacity is not cooled with alternative cooling water sources or dry cooling systems. The noted tradeoffs between greenhouse gas mitigation priorities, freshwater dependency, and vulnerability to climatic events highlight the importance of holistic decision making as regional power grids transition to cleaner generation sources.

The United States (US) energy system is a large water user, but the nature of that use is poorly understood. To support resource comanagement and fill this noted gap in the literature, this work presents detailed estimates for US-based water consumption and withdrawals for the US energy system as of 2014, including both intensity values and the first known estimate of total water consumption and withdrawal by the US energy system. We address 126 unit processes, many of which are new additions to the literature, differentiated among 17 fuel cycles, five life cycle stages, three water source categories, and four levels of water quality. Overall coverage is about 99% of commercially traded US primary energy consumption with detailed energy flows by unit process. Energy-related water consumption, or water removed from its source and not directly returned, accounts for about 10% of both total and freshwater US water consumption. Major consumers include biofuels (via irrigation), oil (via deep well injection, usually of nonfreshwater), and hydropower (via evaporation and seepage). The US energy system also accounts for about 40% of both total and freshwater US water withdrawals, i.e., water removed from its source regardless of fate. About 70% of withdrawals are associated with the once-through cooling systems of approximately 300 steam cycle power plants that produce about 25% of US electricity.

The US power sector is in a state of transition, prompted by significant shifts in technological innovations, energy markets, regulatory structures, and social pressures. As the electricity generation fleet changes, so too does the spatial & temporal distribution of the cooling water requirements for power plants. However, to date, these impacts have yet to be quantified. This study uses power plant-specific fuel consumption, generation, and cooling water use data to assess changes in the water withdrawn and consumed by thermoelectric power plants across 8-digit Hydrologic Unit Code (HUC-8) watersheds between 2008 and 2014. During this period, a few prominent trends are noted, including transitions in generation from coal-fired steam to natural-gas combined cycle units, from once-through cooling to wet recirculating towers and dry cooling systems, and from traditional fresh and saline surface cooling water to reclaimed water and groundwater sources. Total US cooling water withdrawals and consumption volume decreased from 2008 to 2014. The average water withdrawn per unit of electrical output decreased over this time, while changes in water consumption rates stayed relatively flat. Changes in water use at the watershed scale were unevenly distributed, as some water-scarce regions experienced increases in cooling water usage for thermal power plants, while others experienced significant water reductions and environmental benefits, especially where coal-fired generation was retired or retrofitted. The results from this study underscore the importance of evaluating water withdrawals and consumption at local spatial scales, as the water extraction, water quality and environmental health consequences of power plants on downstream users are non-uniform.

With reverse osmosis membranes being industry-standard in many potable reuse facilities, an opportunity exists to desalinate higher-salinity streams (e.g., brine and regional brine interceptor streams) to augment traditional wastewater supplies and reduce brine disposal requirements. This study evaluates the energy consumed in recovering water from these streams at advanced water purification facilities. Scenarios without and with seawater inflow and infiltration at coastal wastewater reclamation facilities are considered. It was found that as wastewater salinity increases with increasing seawater inflow and infiltration, base case energy consumption increases, but the percent increase of energy consumption caused by mixing higher-salinity streams decreases. Multiple energy-saving strategies were evaluated, including energy recovery devices, closed-circuit reverse osmosis, and desalination of the higher-salinity streams separately from the treated wastewater. The energy savings was greater for closed-circuit reverse osmosis than for energy recovery devices and increased for both as influent salinity increases. The energy savings from desalinating higher-salinity streams separately increased as the salinity difference between the two streams increased. Addition of higher-salinity streams was also considered within the context of inorganic scaling potential, product water requirements, and discharge permits that may limit recoveries.

Growing interest in greenhouse gas mitigation strategies to address global climate change has resulted in the rapid expansion of renewable electricity sources. However, increasing power generation from variable renewable electricity sources, such as solar photovoltaics and wind turbines, has made balancing electricity supply and demand across the power grid more challenging. In some regions, high penetrations of variable renewables have also created electricity supply systems where electricity is significantly cleaner in hours when renewable energy is abundant, in comparison with peak demand hours when fossil fuel-based generation is often dominant. In the absence of cost-effective, utility-scale batteries, demand response strategies that leverage flexibility in electricity consumption have gained interest as readily available resources to address the temporal mismatch between renewable energy availability and high energy demand periods. The water industry (i.e., water supply and wastewater systems) includes industrial customers that are particularly attractive in terms of demand response potential as they can offer flexibility through large interruptible pumping loads, large water storage capacities, and energy generation potential. This study explores flexibility strategies in the water sector motivated primarily by the goal of reducing emissions, rather than cost. We present an illustrative case study demonstrating that strategically shifting 5% of the total daily average electricity load of a cluster of 97 water-supply electricity consumers in California across the year can reduce annual carbon dioxide emissions by 2–5%. In the end, important future research directions are discussed to support the implementation of flexibility measures in the water industry.

Intra-national electricity transmission drives virtual water transfer from electricity production regions to electricity consumption regions. In China, the water-intensive thermoelectric power industry is expanding quickly in many water-scarce energy production hubs in northern and northwestern provinces. This study constructed a node-flow model of inter-provincial electricity transmission to investigate the virtual water and scarcity-adjusted virtual water (or virtual scarce water) embodied in the electricity transmission network. It is revealed that total inter-provincial virtual water transfer embodied in electricity transmission was 623 million m3 in 2011, equivalent to 12.7% of the national total thermoelectric water consumption. The top three largest single virtual water flows are West Inner Mongolia-to-Beijing (44 million m3), East Inner Mongolia-to-Liaoning (39 million m3), and Guizhou-to-Guangdong (37 million m3). If the actual volumes of consumptive water use are translated into scarcity-adjusted water consumption based on Water Stress Index, West Inner Mongolia (81 million m3), Shanxi (63 million m3) and Ningxia (30 million m3) become the top three exporters of virtual scarce water. Many ongoing long-distance electricity transmission projects in China will enlarge the scale of scarce water outflows from northwestern regions and potentially increase their water stress.

The nexus between energy, water and agricultural production is important to consider for effective resource management and risk mitigation. New data acquisition techniques, in conjunction with cheap storage applications, have facilitated the collection and analysis of massive datasets to holistically describe natural and built environments. However, the field of coupling energy, water and agricultural management through evolving remote sensing technologies is still nascent. We find that remote sensing technologies are being increasingly utilized for resource management, but there are still large opportunities to deploy these technologies to achieve integrated resource management goals. Thus, this article aims to bridge remote sensing and integrated resource management communities, which have largely developed in isolation, so that technologies can be developed to assist in achieving sustainable development. The opportunities and challenges highlighted in this article can guide technology development, research opportunities and create new interdisciplinary research partnerships.

Characterizing the advantages and disadvantages of different electricity resource mixes in meeting electricity decarbonization goals is an active area of research. Many system-level assessments, however, evaluate different mixes on the basis of minimizing electricity costs without accounting for regional environmental externalities. California represents a highly populated region with both aggressive electricity decarbonization policies and water scarcity issues that are projected to worsen under climate change, representing an interesting case study for assessing the tradeoffs between the costs of electricity decarbonization and water resource consumption. This study therefore combines electric grid dispatch modeling and regional life cycle freshwater consumption data to compare in-state freshwater consumption and levelized cost of electricity for four electricity mix scenarios designed to achieve zero-carbon electricity in California by 2045, compliant with current law (California Senate Bill 100). In modeled scenarios, we find that the lowest costs occurred for mixes with lower energy storage capacity needs enabled by high capacity factor and dispatchable renewables. However these mixes also resulted in high freshwater consumption due largely to heavy reliance on geothermal resources. By contrast, the mix with the lowest freshwater consumption relied exclusively on wind, solar, and hydropower and reduced water consumption by an order of magnitude compared to that of the lowest cost mix. Due to lower capacity factors and greater difficulty in matching supply to demand (increasing energy storage needs), this mix increased the levelized cost of electricity by 30%. Overall, our results show that prioritizing low electricity costs as well as other climate-relevant criteria, such as freshwater consumption, in meeting zero-carbon electricity goals will result in a very different electricity mix than simply considering costs alone.

A modeling framework was developed to evaluate synergistic blending of the waste streams from seawater reverse osmosis (RO) desalination and wastewater treatment facilities that are co-located or in close proximity. Four scenarios were considered, two of which involved blending treated wastewater with the brine resulting from the seawater RO desalination process, effectively diluting RO brine prior to discharge. One of these scenarios considers the capture of salinity-gradient energy. The other two scenarios involved blending treated wastewater with the intake seawater to dilute the influent to the RO process. One of these scenarios incorporates a low-energy osmotic dilution process to provide high-quality pre-treatment for the wastewater. The model framework evaluates required seawater and treated wastewater flowrates, discharge flowrates and components, boron removal, and system energy requirements. Using data from an existing desalination facility in close proximity to a wastewater treatment facility, results showed that the influent blending scenarios (Scenarios 3 and 4) had several advantages over the brine blending scenarios (Scenarios 1 and 2), including: (1) reduced seawater intake and brine discharge flowrates, (2) no need for second-pass RO for boron control, and (3) reduced energy consumption. It should be noted that the framework was developed for use with co-located seawater desalination and coastal wastewater reclamation facilities but could be extended for use with desalination and wastewater reclamation facilities in in-land locations where disposal of RO concentrate is a serious concern.

Author(s): Porse, E; Mika, KB; Escriva-Bou, A; Fournier, ED; Sanders, KT; Spang, E; Stokes-Draut, J; Federico, F; Gold, M; Pincetl, S | Abstract: Reducing energy consumption for urban water management may yield economic and environmental benefits. Few studies provide comprehensive assessments of energy needs for urban water sectors that include both utility operations and household use. Here, we evaluate the energy needs for urban water management in metropolitan Los Angeles (LA) County. Using planning scenarios that include both water conservation and alternative supply options, we estimate energy requirements of water imports, groundwater pumping, distribution in pipes, water and wastewater treatment, and residential water heating across more than one hundred regional water agencies covering over 9 million people. Results show that combining water conservation with alternative local supplies such as stormwater capture and water reuse (nonpotable or indirect potable) can reduce the energy consumption and intensity of water management in LA. Further advanced water treatment for direct potable reuse could increase energy needs. In aggregate, water heating represents a major source of regional energy consumption. The heating factor associated with grid-supplied electricity drives the relative contribution of energy-for-water by utilities and households. For most scenarios of grid operations, energy for household water heating significantly outweighs utility energy consumption. The study demonstrates how publicly available and detailed data for energy and water use supports sustainability planning. The method is applicable to cities everywhere.

Increasing water competition, population growth and global climate change will intensify the tension between water and energy resources in arid climates of the world, since energy costs underscore the challenges facing water security in dry regions. In few places is the tension between water and energy resources more pronounced than in Los Angeles, California. This article analyzes the city’s current water supply and estimates its future energy requirements based on water supply projections from the Los Angeles Department of Water and Power. Results suggest that while increasing local water management strategies could reduce the future energy intensity of the water supply, an increased reliance on water transfers could worsen its future energy intensity.

Water heating represented nearly 13% of 2010 residential energy consumption making it an important target for energy conservation efforts. The objective of this work is to identify spatially-resolved strategies for energy conservation, since little analysis has been done to identify how regional characteristics affect the energy consumed for water heating. We present a first-order thermodynamic analysis, utilizing ab initio calculations and regression methods, to quantify primary energy consumption and CO2 emissions with regional specificity by considering by considering local electricity mixes, heat rates, solar radiation profiles, heating degrees days, and water heating unit sales for 27 regions of the US. Results suggest that shifting from electric towards natural gas or solar water heating offered primary energy and CO2 emission reductions in most US regions, but these reductions varied considerably according to regional electricity mix and solar resources. We find that regions that would benefit most from technology transitions, are often least likely to switch due to limited economic incentives. Our results suggest that federal energy factor metrics, which ignore upstream losses in power generation, are insufficient in informing consumers about the energy performance of residential end use appliances.

Despite the water intensity of hydraulic fracturing, recent life cycle analyses have concluded that increased shale gas development will lead to net decreases in water consumption if the increased natural gas production is used at natural gas combined cycle power plants, shifting electricity generation away from coal-fired steam cycle power plants. This work expands on these studies by estimating the spatial and temporal patterns of changes in consumptive water use in Texas river basins during a period of rapid shale gas development and use in electricity generation from August 2008 through December 2009. While water consumption decreased in Texas overall, some river basins saw increased water consumption and others saw decreased water consumption, depending on the extent of extraction activity in the basin, the mix of power plants using cooling water in that basin, and price-based changes in the power sector. Due to the temporal and spatial heterogeneity in the consumptive water impacts of natural gas de...

Hydraulic fracturing faces several environmental challenges: the process is highly water-intensive, generates significant volumes of wastewater, and is associated with widespread flaring of coproduced natural gas. One possible solution to simultaneously mitigate these challenges is to use energy from flared natural gas for on-site wastewater treatment, thereby reducing flared gas, volumes of wastewater, and volumes of freshwater necessary for subsequent shale production as treated wastewater could be reused. This study builds an analytical framework for understanding the feasibility of this approach. We concluded that the thermal energy required to treat wastewater from the first 10 days after well completion is 148000–865000 MJ (140–820 MMBTU) and would generate 750–6800 m3 of treated water. Additionally, using the volume of flared natural gas in Texas in 2012, the theoretical maximal volume of treated water that could be generated was calculated to be 180–540 million m3, representing approximately 3–9% ...

The efficiency of a thermoelectric generator is dependent on a number of operational and climatic variables, including ambient air temperature. To date, there has not been a data-driven analysis of the impacts of climate variability on electricity generator performance that includes a statistically representative set of generators. This study develops regression models to estimate changes in the efficiencies of over one thousand coal and natural gas generators as a function of ambient air temperature and operational variables, across different fuel types, prime movers, cooling systems, and climate zones during the years ranging from 2008 to 2017. The efficiencies of generators with dry cooling, particularly those in hot and dry climates, demonstrated the greatest sensitivity to increases in ambient temperature. Results for generators utilizing wet cooling systems were largely inconclusive, most likely because other factors, such as cooling water temperature, are better predictors of efficiency. Natural gas combustion generator efficiencies exhibit large sensitivities to rises in air temperature in theoretical models but had a counterintuitive trend in our findings, where losses were relatively small in the hottest and driest climates. This result is likely due to the fact that natural gas combustion generators in hot and arid regions often utilize inlet air cooling technologies to reduce the temperature of ambient air before it enters the compressor, thereby mitigating efficiency losses. The analytical framework developed offers generalized methods for cleaning, processing, and merging federally available electricity generation and climate datasets to increase their value in future studies.

Water consumption from electricity systems can be large, and it varies greatly by region. As electricity systems change, understanding the implications for water demand is important, given differential water availability. This letter presents regional water consumption and consumptive intensities for the United States electric grid by region using a 2014 base year, based on the 26 regions in the Environmental Protection Agency’s Emissions & Generation Resource Integrated Database. Estimates encompass operational (i.e. not embodied in fixed assets) water consumption from fuel extraction through conversion, calculated as the sum of induced water consumption for processes upstream of the point of generation (PoG) and water consumed at the PoG. Absolute water consumption and consumptive intensity is driven by thermal power plant cooling requirements. Regional consumption intensities vary by roughly a factor of 20. This variability is largely attributed to water consumption upstream of the PoG, particularly evaporation from reservoirs associated with hydroelectricity. Solar and wind generation, which are expected to continue to grow rapidly, consume very little water and could drive lower water consumption over time. As the electricity grid continues to change in response to policy, economic, and climatic drivers, understanding potential impacts on local water resources can inform changes.

Vast natural resources and strained water supplies make Mexico a valuable geographic setting for studying the energy-water nexus. While Mexico has historically been a major oil producing country, it struggles with water stress, as much of its land area is experiencing or approaching physical water scarcity. Solving many of Mexico's water issues will require energy for extracting, transporting, and treating water where it is needed most. Yet such energy use is not always possible since many people are not connected to an electricity grid or other decentralized energy infrastructure. In addition, a continuation of the almost decade-long trend of declining oil production and exports might reduce revenues and available energy to fund and operate new water systems. Consequently, there is an opportunity to improve water services through use of distributed renewable energy technologies that do not directly require fossil resources or large-scale infrastructure. Various policies and technologies are relevant to the energy-water nexus on a decentralized scale, which are covered in this manuscript. We use an integrated technology policy framework to assess the efficacy of integrating renewable energy and water systems in Mexico via case studies of technologies affecting energy-water policy objectives and

The current California drought has reduced freshwater availability, creating tensions between water users across the state. Although over 518 million m 3 of water were produced during fossil fuel production in California in 2014, the majority was disposed into Class II injection wells. There have been few attempts to assess the feasibility of using produced water for beneficial purposes, due in part to the difficulties of accessing, synthesizing and analyzing data regarding produced water quality and quantity. This study addresses this gap and provides a techno-economic assessment of upgrading produced water from California’s oil and natural gas activities and moving it to adjacent water-stressed regions. Results indicate that the four population centers facing the greatest water shortage risk are located in the Central Valley within a 161 km (100 mile) radius of 230 million m 3 of total treatable produced water. This volume can supply up to one million people-years worth of potable water. The cost of desalinating and transporting this water source is comparable in magnitude to some agricultural and local public water supplies and is substantially lower than bottled water. Thus, utilizing reverse osmosis to treat produced water might be a feasible solution to help relieve water scarcity in some drought-stricken regions of California.

Developing strategies to reduce the air quality and greenhouse gas (GHG) emissions associated with power generation has been a priority across environmental and research communities for many years. Likewise, reducing the freshwater impacts of the power sector has become of increasing interest, prompted by water-stress and heat waves in many regions of the United States. However, there has been very little quantification of the environmental trade-offs between water consumption and air emissions in the power generating industry. Without simultaneously evaluating these environmental variables, solutions aimed to address one environmental priority might lead to unintended consequences in the other. Bridging this research gap will provide a more holistic perspective on the environmental trade-offs associated with electricity generation. This study investigates environmental tradeoffs in the electricity generation sector by quantifying the temporally-resolved water use and emissions rates of power plants within the Electric Reliability Council of Texas (ERCOT), the independent system operator that governs the provision of electricity for the majority of Texas. A unit commitment and dispatch model, which simulates the cost-minimized dispatching algorithm used by ERCOT, is used to quantify hourly data in terms of water consumption, emissions (i.e. carbon dioxide, nitrogen oxides, and sulfur oxides), and marginal heat rates for 252 electric generation units in ERCOT across a sample historical year. Annual, seasonal, and daily variations are assessed. The results of this study are intended to inform more balanced decision making and environmental assessments for the power generation sector moving forward.

Electricity generation often requires large amounts of water, most notably for cooling thermoelectric power generators and moving hydroelectric turbines. This so-called "electricity-water nexus" has received increasing attention in recent years by governments, nongovernmental organizations, industry, and academics, especially in light of increasing water stress in many regions around the world. Although many analyses have attempted to project the future water requirements of electricity generation, projections vary considerably due to differences in temporal and spatial boundaries, modeling frameworks, and scenario definitions. This manuscript is intended to provide a critical review of recent publications that address the future water requirements of electricity production and define the factors that will moderate the water requirements of the electric grid moving forward to inform future research. The five variables identified include changes in (1) fuel consumption patterns, (2) cooling technology preferences, (3) environmental regulations, (4) ambient climate conditions, and (5) electric grid characteristics. These five factors are analyzed to provide guidance for future research related to the electricity-water nexus.

The power sector is responsible for approximately one-half of the United States’ annual water withdrawals and approximately 3% of its annual water consumption. The majority of this water is devoted to cooling thermoelectric power plants by means of once-through or recirculating cooled systems. Despite the large water requirements of the power sector, water conservation strategies are typically concentrated in the urban and agricultural sectors. Although national agencies such as the United States Geological Survey and the Energy Information Administration do publish data regarding the water use requirements of power plants, these data are often incomplete, inaccurate, and are published infrequently. Consequently, data resolving the temporal variability of water use by the power sector are largely non-existent, making conservation strategies difficult to construct. This analysis utilizes a unit commitment and dispatch (UCD however, water consumption data (i.e., the subset of water withdrawals that is evaporated) has not been reported since 1995. The US Energy Information Administration (EIA) reports cooling water consumption and withdrawal data annually for thermoelectric power generators through its EIA-860 form based on flow rate, but these data are often missing or erroneous, and lack temporal fidelity. There are two types of cooling technologies that are used by the majority of EGUs in the US. Once-through (OT) cooling technologies withdraw large amounts of water from a river or water reservoir, use the water once to cool the hot steam exiting the turbine during power production, and then discharge the warm cooling water back to the original water reservoir. During this process, very little water is lost to evaporation since the water is only used once for cooling. Recirculating cooling systems, by contrast withdraw smaller volumes of water by recycling the water within cooling towers. Since water is cycled multiple times, most of the water that is withdrawn from the original water source is ultimately lost to evaporation, that is, it is consumed. Unlike OT cooling systems, RC cooling systems do not discharge large quantities of water back into the native water reservoirs. Because of these differences in operational water requirements and varying impacts on the cooling source water reservoir, there are tradeoffs between these two technologies. OT cooling systems withdraw large volumes of water, but consume very little, which is therefore good for water availability compared to high water consumption technologies. RC systems require smaller volumes of water, but very little (if any) of the water that is extracted from a reservoir is ultimately returned to the water shed after generation. RC systems, therefore, can be less prone to generation disruptions in areas where water is constrained, but have larger evaporative losses than OT systems. The distribution of OT and RC cooled EGUs varies regionally. Thermoelectric power generators in the western US use a larger fraction of RC cooling systems since the region is generally drier than the comparatively water-rich Eastern US. Eighty percent of the units of electricity generated in the eight most Western US (including Oregon, Washington, Idaho, Montana, Arizona, Nevada, New Mexico, and California) was produced in RC cooled facilities in 2005. (The majority of electricity generated in OT cooled facilities was produced along the coast and using saline cooling water.) By contrast, 54% and 46% of the electricity generated in the remainder of the Eastern US states is derived from OT and RC cooled facilities, respectively. This trend reflects the fact that the Eastern US generally has more water available for withdrawal-intensive cooling facilities. (Table 1 details 2005 water use for thermoelectric electricity production in Eastern and Western US states.) The Western Electricity Coordinating Council (WECC) is the regional entity within the North American Electric Reliability Corporation that coordinates and promotes reliable bulk power transmission across the western United States (i.e. Washington, Oregon, California, Idaho, Nevada, Utah, Arizona, Colorado, Wyoming, as well as portions of Montana, South Dakota, New Mexico, and Texas), Baja California, Mexico, and western Canada. The WECC power grid provides a valuable case study for this research because it is the largest regional power coordination entity in North America, serving approximately 82 million people across 1.8 million square miles and includes the majority of North American regions that have experienced “extreme” or “exceptional” drought in the past decade.

We utilize a unit commitment and dispatch model to estimate how water use fees on power generators would affect dispatching and water requirements by the power sector in the Electric Reliability Council of Texas' (ERCOT) electric grid. Fees ranging from 10 to 1000 USD per acre-foot were separately applied to water withdrawals and consumption. Fees were chosen to be comparable in cost to a range of water supply projects proposed in the Texas Water Development Board's State Water Plan to meet demand through 2050. We found that these fees can reduce water withdrawals and consumption for cooling thermoelectric power plants in ERCOT by as much as 75% and 23%, respectively. To achieve these water savings, wholesale electricity generation costs might increase as much as 120% based on 2011 fuel costs and generation characteristics. We estimate that water saved through these fees is not as cost-effective as conventional long-term water supply projects. However, the electric grid offers short-term flexibility that conventional water supply projects do not. Furthermore, this manuscript discusses conditions under which the grid could be effective at "supplying" water, particularly during emergency drought conditions, by changing its operational conditions.

The State of Texas faces considerable challenges meeting increasing water and power demands due to population and economic growth within the context of a hot and drought-prone climate. In its year 2012 State Water Plan, the Texas Water Development Board recommends investing more than $53 billion in traditional water supply projects to meet demands through 2060. While a significant fraction of the state's water supplies are used to produce electricity, water conservation schemes through changes in the power sector are not considered in the state's water plans. This study estimates the generation costs, water withdrawals, and water consumption from meeting Texas' 2011 electricity demands under three scenarios: minimizing (1) water withdrawals, (2) water consumption, and (3) marginal generation costs. To conduct the study, we use a dispatch model of the ERCOT power grid in a sample historical year (2011) to quantify the potential water savings and economic costs that might be incurred by optimizing power generation in Texas. Under current grid operations (minimizing marginal generation costs), Texas' year 2011 electricity demands cost $8.2 billion to generate, withdrew 4,600 billion gallons of water, and consumed 101 billion gallons of water. If electricity was produced to minimize water withdrawals (instead of minimizing generation cost), we estimate withdrawals would reduce by an order of magnitude, consumption would reduce by 30%-40%, and generation costs would increase by 25%. Minimizing for water consumption, we estimate water consumption is reduced by 40%-50%, withdrawals increase by up to 75%, and generation costs increase by 25%. Minimizing water consumption in the power sector promotes generation from once-through, open-cooled plants, which withdraw relatively more water but consume relatively less. The total water supplied by projects in the state's current water plan is around 4,600 billion gallons by 2060. We estimate the feasible reductions in water withdrawn and consumed by Texas' current power grid is around 4,000 - 6,000 billion gallons and 40-60 billion gallons, respectively, depending on the price of natural gas. While our analysis demonstrates increases in generation costs from reducing water consumption in the power sector, those costs are lower per gallon of water than many other water supply projects identified in Texas' State Water Plan. These results suggest that water planners should consider water saving opportunities in the power sector as one potentially cost-effective option.

The US food system utilizes large quantities of liquid fuels, electricity, and chemicals yielding significant greenhouse gas (GHG) emissions that are not considered in current retail prices, especially when the contribution of biogenic emissions is considered. However, because GHG emissions might be assigned a price in prospective climate policy frameworks, it would be useful to know the extent to which those policies would increase the incremental production costs to food within the US food system. This analysis uses lifecycle assessment (LCA) to (1)?estimate the magnitude of carbon dioxide equivalent (CO2e) emissions from typical US food production practices, using wheat and beef as examples, and (2)?quantify the cost of those emissions in the context of a GHG-pricing regime over a range of policy constructs. Wheat and beef were chosen as benchmark staples to provide a representative range of less intensive and more intensive agricultural goods, respectively. Results suggest that 1.1???0.13 and 31???8.1?kg of lifecycle CO2e emissions are embedded in 1?kg of wheat and beef production, respectively. Consequently, the cost of lifecycle CO2e emissions for wheat (i.e. cultivation, processing, transportation, storage, and end-use preparation) over an emissions price range of?$10 and $85 per tonne CO2e is estimated to be between $0.01 and $0.09 per kg of wheat, respectively, which would increase total wheat production costs by approximately 0.3?2% per kg. By comparison, the estimated lifecycle CO2e price of beef over the same range of CO2e prices is between?$0.31 and $2.60 per kg of beef, representing a total production cost increase of approximately 5?40% per kg based on average 2010 food prices. This range indicates that the incremental cost to total US food production might be anywhere between?$0.63?5.4?Billion per year for grain and $3.70 and $32?Billion per year for beef based on CO2e emissions assuming that total production volumes stay the same.

This letter consists of a first-order analysis of the primary energy embedded in water in the United States. Using a combination of top-down sectoral assessments of energy use together with a bottom-up allocation of energy-for-water on a component-wise and service-specific level, our analysis concludes that energy use in the residential, commercial, industrial and power sectors for direct water and steam services was approximately 12:3 0:3 quadrillion BTUs or 12.6% of the 2010 annual primary energy consumption in the United States. Additional energy was used to generate steam for indirect process heating, space heating and electricity generation.

The need for energy in water provision and use is obvious, however the drivers are often complex, difficult to assess, and often inconsistently presented. Here we build a clearer definition and conceptual framework of “water-related energy”. We apply this framework to harmonise data and results across disparate studies so that regional estimates of water-related energy can be compared in a consistent way for the first time. We show how widely different boundaries have been used for analysis including or excluding: water and wastewater utilities, as well as residential, commercial, industrial, and agricultural water users. Consequently, understanding of what constitutes “water-related energy” is widely divergent. We demonstrate how up to 12.6% of total national primary energy use can be influenced by water, when (i) water-related energy of water users, and (ii) energy use by water utilities, are all included. Water heating for residential, commercial, and industrial purposes is the dominant fraction. Water and wastewater utilities use 0.4–2.3% of primary energy or 0.6–6.2% of regional electricity, mostly for water pumping. This is substantial, but lower than frequent claims in the media and reports. To answer how is miscommunication influencing policy? we undertake a novel systematic tracking of communication to demonstrate distortion between research and its application in government reports, media and policy. We show that significant confusion is caused by (i) unclear or inconsistent boundaries (ii) widely differing use of terms for water “system”, “sector”, and “supply”, (iii) frequent failure to distinguish ‘energy’ from ‘electricity’ and (iv) wide use of non-standard units. While acknowledging that media is often less accurate than government reports, and that peer-reviewed articles generally have highest overall quality, we observe miscommunication and inconsistency in all publication forms. We argue a global protocol is needed to improve consistency of analysis and sharpen policy towards sustainable water end use because this is where most water-related energy occurs. We establish a foundational framework and definitions for this protocol while recognising much more needs to be done. The strong practical and theoretical implications of the work for sustainable cleaner production are elucidated. This is timely, as global quantification of water-related energy has yet to occur particularly for water end-use which is the dominant component.