William B. Mills

Projecting Water Withdrawal and Supply for Future Decades in the U.S. under Climate Change Scenarios

The sustainability of water resources in future decades is likely to be affected by increases in water demand due to population growth, increases in power generation, and climate change. This study presents water withdrawal projections in the United States (U.S.) in 2050 as a result of projected population increases and power generation at the county level as well as the availability of local renewable water supplies. The growth scenario assumes the per capita water use rate for municipal withdrawals to remain at 2005 levels and the water use rates for new thermoelectric plants at levels in modern closed-loop cooling systems. In projecting renewable water supply in future years, median projected monthly precipitation and temperature by sixteen climate models were used to derive available precipitation in 2050 (averaged over 2040-2059). Withdrawals and available precipitation were compared to identify regions that use a large fraction of their renewable local water supply. A water supply sustainability risk index that takes into account additional attributes such as susceptibility to drought, growth in water withdrawal, increased need for storage, and groundwater use was developed to evaluate areas at greater risk. Based on the ranking by the index, high risk areas can be assessed in more mechanistic detail in future work.

Analysis of water temperatures in Conowingo Pond as influenced by the Peach Bottom atomic power plant thermal discharge

Abstract Numerical surface water hydrodynamic and transport models have been traditionally applied to predict power plant thermal impacts under design conditions. The need to understand both thermal impacts and receiving water biogeochemical impacts and associated ecological and health risks under highly variable transient conditions on seasonal to annual time scales necessitates the use of predictive multidimensional modeling systems. Over the last decade, three-dimensional hydrodynamic and reactive transport modeling has matured from a research subject to a practical analysis technology. Simultaneously, computational requirements for realistic three-dimensional modeling have changed from super computers and high-end workstations to economical commodity personal computers. This paper describes a three-dimensional surface water model system, the Environmental Fluids Dynamics Code (EFDC), capable of addressing a variety of power plant impact issues, including thermal transport, water quality-eutrophication, and toxic contaminant transport and fate, in surface water systems. The development history of the model and its previous applications, as well as its theoretical and computational formulations are presented. Model extensions addressing coupled near- and far-field thermal transport due to high velocity cooling water discharges are discussed in detail. To illustrate the model’s capabilities, preliminary results of thermal transport in Conowingo Pond associated with the Peach Bottom Atomic Power Station’s (PBAPSs) discharge are presented and compared with field observations.

Comparison of multimedia model predictions for a contaminant plume migration scenario.

Abstract Predictions of four risk assessment models — RESRAD, PRESTO, MMSOILS, and MEPAS — for a test scenario involving the migration of a single, rapidly transforming radionuclide, 90Sr, and a persistent, long radionuclide chain, 234U and its progeny, in groundwater are compared. All four models make comparable predictions for the plume centerline concentrations of the primary contaminants in the aquifer for a distance of up to about 300 m from the source. MEPAS, MMSOILS, and RESRAD make similar predictions for the transverse concentration profiles in the aquifer. The four models make considerably different predictions for the temporal concentration profiles of the progeny in the aquifer. The profiles differ in shape, magnitude of the peak, and in width. The differences are a result of the simplifying assumptions underlying each of the models.

Sensitivity of Concentration and Risk Predictions in the PRESTO and MMSOILS Multimedia Models: Regression Technique Assessment

Application of Executive Order 12898 to risk assessment of highway or rail transport of hazardous materials has proven difficult; the location and conditions affecting the propagation of a plume of hazardous material released in a potential accident are unknown, in general. Therefore, analyses have only been possible in geographically broad or approximate manner. The advent of geographic information systems and development of software enhancements at Sandia National Laboratories have made kilometer-by-kilometer analysis of populations tallied by U.S. Census Blocks along entire routes practicable. Tabulations of total, or racially/ethnically distinct, populations close to a route, its alternatives, or the broader surrounding area, can then be compared and differences evaluated statistically. This paper presents methods of comparing populations and their racial/ethnic compositions using simple tabulations, histograms and Chi Squared tests for statistical significance of differences found. Two examples of these methods are presented: comparison of two routes and comparison of a route with its surroundings.This paper describes the application of two multimedia models, PRESTO and MMSOILS, to predict contaminant migration from a landfill that contains an organic chemical (methylene chloride) and a radionuclide (uranium-238). Exposure point concentrations and human health risks are predicted, and distributions of those predictions are generated using Monte Carlo techniques. Analysis of exposure point concentrations shows that predictions of uranium-238 in groundwater differ by more than one order of magnitude between models. These differences occur mainly because PRESTO simulates uranium-238 transport through the groundwater using a one-dimensional algorithm and vertically mixes the plume over an effective mixing depth, whereas MMSOILS uses a three-dimensional algorithm and simulates a plume that resides near the surface of the aquifer.A sensitivity analysis, using stepwise multiple linear regression, is performed to evaluate which of the random variables are most important in producing the predicted distributions of exposure point concentrations and health risks. The sensitivity analysis shows that the predicted distributions can be accurately reproduced using a small subset of the random variables. Simple regression techniques are applied, for comparison, to the same scenarios, and results are similar. The practical implication of this analysis is the ability to distinguish between important versus unimportant random variables in terms of their sensitivity to selected endpoints.

Projecting and Forecasting Winter Precipitation Extremes and Meteorological Drought in California Using the North Pacific High Sea Level Pressure Anomaly

AbstractLarge-scale climatic indices have been used as predictors of precipitation totals and extremes in many studies and are used operationally in weather forecasts to circumvent the difficulty in obtaining robust dynamical simulations of precipitation. The authors show that the sea level pressure North Pacific high (NPH) wintertime anomaly, a component of the Northern Oscillation index (NOI), provides a superior covariate of interannual precipitation variability in Northern California, including seasonal precipitation totals, drought, and extreme precipitation intensity, compared to traditional ENSO indices such as the Southern Oscillation index (SOI), the multivariate ENSO index (MEI), Nino-3.4, and others. Furthermore, the authors show that the NPH anomaly more closely reflects the influence of Pacific basin conditions over California in general, over groups of stations used to characterize statewide precipitation in the Sierra Nevada range, and over the southern San Francisco Bay region (NASA Ames R...

Predictions of Relative Sea-Level Change and Shoreline Erosion over the 21st Century on Tangier Island, Virginia

Abstract For approximately 300 years, Tangier Island, located in the middle of the Chesapeake Bay, USA, has been continuously populated by up to 1,000 residents. At present, the population is near 700. The island is very flat and low, and residents live on three sandy ridges with elevations of about 1.0–1.5 m above mean sea level (msl). Over the past century, the relative sea level there has risen about 31 cm, in part due to the estimated subsidence of the island (in other parts of the Bay as well) at a rate of about 18 cm per century. As the level of the sea continues to rise in the 21st century and as shoreline erosion continues, the very existence of the island is in jeopardy. In this article, projections are made to the year 2100 in terms of how sea-level rise and continued shoreline erosion will impact the island. To evaluate impacts, several years of historical tidal levels were extrapolated to the year 2100, using the predicted sea-level changes. The predictions were compared with the observed levels in year 2000 to show the effects of relative sea-level change. Shoreline erosion was also examined. The first map with enough accuracy to correctly depict temporal changes in shoreline was from 1850. When that map of Tangier Island was then compared with more recent ones, it was found that erosion was much more severe on the western shore due to the longer fetch over which wind-generated waves could develop. Implications for continued human habitation to the year 2100 were examined and the future island size was projected, assuming no additional human intervention beyond the present.

Small Island States in Indian and Atlantic Oceans: Vulnerability to Climate Change and Strategies for Adaptation

Small Island Developing States (SIDS) are among the world’s nations that are most vulnerable to climate change. SIDS have neither the resources nor the expertise to effectively evaluate the risks associated with climate change, nor the ability to adapt to potential changes. Compared to islands in the Pacific Ocean and the Caribbean Sea, SIDS in the Indian Ocean and eastern Atlantic Ocean off of the west coast of Africa are among the poorest and least studied of the SIDS. In this United Nations supported study, five Indian Ocean SIDS (Comoros, Madagascar, Mauritius, Seychelles, and Maldives) and two Atlantic Ocean SIDS (Cape Verde, and the Republic of Sao Tome & Principe) are evaluated for their vulnerability to climate change, with an emphasis on impacts on water resources and coastal zone resources. Due to significant differences between the SIDS studied in terms of size, topography, geology, precipitation, population density, storm patterns and intensities, relative sea level rise, indicators of wealth (such as GDP/capita), and other island characteristics, each SIDS faces its own unique challenges. This paper describes the major findings of the study. One important finding is that relative sea level rise at present appears most significant on one of the SIDS (Maldives), and a number of other SIDS appear to be emerging slightly at a rate high enough to presently offset the effects of global sea level rise. However, analysis shows that at sometime during the 21 st century, should sea level rise accelerate as climate models now suggest, that all the SIDS will become vulnerable to sea level change. Further, an existing stress on most of the SIDS is the human population density and tourism that have increased dramatically at most SIDS over the past several decades. Tourism provides both economic benefits to the islands, while at the same time tourists consume resources at rates typically far in excess of the native population. Therefore, stresses on water resources and the coastal zone due to human population are factored into the climate change stresses that are projected to increase over this century. Finally the paper describes capacity building efforts and strategies for adaptation that are intended to bring attention, resources, and expertise to the aid of the SIDS. One vehicle to do this is through the development of an Internet portal, eventually to be hosted and maintained by one of the SIDS.

Potential Environmental Impacts of Hydrogen-based Transportation and Power Systems

A model of hydrogen dynamics in the troposphere and stratosphere has been developed. The model is intended to complement more complex three-dimensional models, such as GATORGCMOM (Jacobson, 2009). The model presented here, while unable to simulate the wide array of processes parameterized in numerical three-dimensional models, can simulate atmospheric hydrogen mixing ratios over time periods that extend from well into the past to well into the future (for example, from the beginning of the industrial revolution to the end of the 21 century) in a matter of minutes while at the other extreme, GATOR-GCMOM can take weeks of real time to simulate a decade. The simplified model can predict how atmospheric hydrogen mixing ratios will be affected by conversion to an alternative hydrogen economy (e.g., to hydrogen fuel cell vehicles). Model verification and validation tests have been completed, and are reported here as well. Multiple sources and sinks of hydrogen are included in the global model. The model also predicts the total atmospheric burden and lifetime of hydrogen. The historical period from 1992 to present shows that the model can predict the recent hydrogen mixing ratios in the troposphere, (approximately 531 ppbv globally averaged). Hypothetical market conversion scenarios are simulated, and predicted hydrogen mixing ratios have been simulated up to the end of the 21 century. Introduction Research over the past decade on hydrogen fuel cell vehicles (HFCVs) has been carried out to examine whether HFCVs can provide a low carbon alternative to gasoline powered vehicles. Several researchers have voiced concerns that the amount of fugitive hydrogen released to the atmosphere would substantially increase, primarily by leakage into the troposphere from production, distribution and storage of hydrogen and could adversely impact the stratosphere. Tromp et al. (2003) estimated 10% to 20% of the amount of molecular hydrogen anthropogenically generated could be leaked into the troposphere, which is equivalent to between 60 and 120 Tg/year, assuming a 100 percent change in the future of all technologies based on oil or gasoline. Tromp et al. predict these emission increases, and associated atmospheric chemistry reactions, could cause tropospheric hydrogen concentrations to increase