Perched water zones have been identified in the fractured, welded tuff in the semiarid to arid environments of Yucca Mountain, Nevada and near Superior, Arizona. An understanding of the formation of such zones is necessary in order to predict where future perched water might form at Yucca Mountain, the proposed site of a high-level nuclear waste repository. The formation or growth of a perched zone above a repository is one factor of the factors to be considered in the risk assessment of the Yucca Mountain site. The Apache Leap Research Site (ALRS) near Superior, Arizona is a natural analog to the Yucca Mountain site in terms of geology, hydrology, and climate. Perched water has been identified over an area of at least 16 km² in the Apache Leap Tuff, a mid- Miocene fractured, welded ash-flow tuff. A primary goal of this investigation was to characterize the physical and hydrologic properties of the tuff in the region above and including the perched zone, and to evaluate those characteristics to develop a model for a perching mechanism in the tuff. A second goal was to determine what fraction of water entering a watershed reaches the subsurface, to potentially recharge the perched zone. The Apache Leap Tuff has been subject to considerable devitrification and vapor phase crystallization, which dominate the character of the rock. With depth to the perched zone, pumice fragments become increasingly flattened and segregated; the pumice fragments are the primary locations of porosity in the rock, therefore porosity also becomes greatly reduced with depth, to the extent that the rock matrix is virtually impermeable at the perched water zone. Fractures are the primary pathways by which water moves through the rock; fracture hydraulic conductivity values were determined to be nine orders of magnitude greater than measured matrix hydraulic conductivity at the perched zone. An increase in fracture filling by silica mineralization beneath the perched zone reduces the secondary permeability, enhancing the formation of perched water. Thus, the primary mechanisms for the formation of the perched zone include fracture flow bringing water into the subsurface, combined with extremely low matrix hydraulic conductivity at depth, and reduced secondary permeability by filled fractures and lower fracture density. Water budgets were calculated for two years in a 51.4-ha watershed. Direct measurements were made of precipitation and runoff', evapotranspiration was both directly measured, and modeled based on measurement of a number of weather parameters. Infiltration was calculated as the residual of precipitation after runoff and evapotranspiration were removed. Infiltration was determined to be less than 10% of the annual water budget; evapotranspiration removes on the order of 90% of precipitation on an annual basis.

Numerous small alpine glaciers occupy the high elevation regions of the central and southern Siena Nevada, California. These glaciers change size in response to variations in climate and are therefore important indicators of climate change. An inventory based on USGS topographic maps (l :24,000) revealed 1719 glaciers and perennial snow and ice features for a total area of 39.l5 ±7.52 km2. The number of 'true' glaciers, versus non-moving ice, is estimated to be 118, covering 15.87 ± 1.69 Km2. All glaciers were located on north to northeast aspects, at elevations >3000 m. Historical photographs, geologic evidence, and field mapping were used to determine the magnitude of area loss over the past century at 14 glaciers. These glaciers decreased in area by 31% to 78%, averaging 55%. The rate of area change was determined for multiple time periods for a subset of seven glaciers. Rapid retreat occurred over the first half of the twentieth century beginning in the 1920s in response to warm/dry conditions and continued through the mid-1970s. Recession ceased during the early 1980s, when some glaciers advanced. Since the 1980s each of the seven study glaciers resumed retreat. The uniform timing of changes in area amongst study glaciers suggests a response to regional climate, while the magnitude of change is influenced by local topographic effects. Glacier area changes correlate with changes in spring and summer air temperatures. Winter precipitation is statistically unrelated to changes in glacier area. Headwall cliffs above the glaciers alter the glacier responses by reducing incoming shortwave radiation and enhancing snow accumulation via avalanching.

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Orbicular and comb layer textures in igneous environments are evidence of an unusual heating and cooling regime in small pockets at the edges of crystallizing magmas. Changes in the composition of a magma spark rapid changes in temperature, which cause the temporary suppression of normal crystal nucleation. As the superheated or supercooled magma returns to equilibrium temperature, crystallization occurs exclusively on pre-existing nucleation surfaces (floating xenoliths or wall rocks), creating orbicular and comb layering textures. Orbs and comb layers collected from two localities in the central Sierra Nevada Batholith were analyzed to determine 1) how they formed and 2) what their formation history reveals about the emplacement histories of their respective host plutons. Geochemical analysis including XRF, U-Pb dating and Sr-Nd and O isotope analysis was used to constrain the characteristics of the orbicular magma. Cathodoluminescence as well as macro and microscale petrography was used to determine the specific growth history of the orbs and comb layers. This study shows that orbs and comb layers from both localities formed due to superheating caused by the influx of water into the orbicular melt. Subsequent cooling was caused by mixing–induced depolymerization and fluid enrichment (Big Meadows Creek) or emplacement into a cooler host rock (Deer Creek). Both locations studied are 2–3 Ma younger than their host plutons, indicating that the processes which form orb and comb layers may cause late melting and magma remobilization in larger plutons.

Communities of granivorous desert rodents are structured by habitat selection and may be influenced by either predatory risk or resources. To examine these hypotheses, I manipulated illumination using lanterns, parachute canopies, or natural moonlight and resources using seeds. Foraging behavior is risk-sensitive; increased illumination reduces foraging in open areas while adding shadows to open areas using parachutes increases foraging there. Foraging behavior is also affected by resource enrichments. Differences among species in habitat selection were determined by specific abilities to detect and avoid predators. The least vulnerable species, Dipodomys deserti, foraged heavily in the open and was largely unaffected by treatments; other species of kangaroo rats and kangaroo mice also prefer the open, but responded to both risk and resource manipulations; highly vulnerable Peromyscus maniculatus was always restricted to bushes even under the most favorable circumstances; Perognathus longimembris was restricted to bushes in the absence of P. maniculatus in 1980 and was displaced from preferred microhabitats by the presence of kangaroo rats in 1981. A correlation between auditory bullar volume and use of open habitat by the various species in this community suggests that predatory risk provides an axis along which habitat segregation occurs. Predation can shape community structure by influencing foraging decisions of individuals. Desert rodents from North America and the Middle East have converged morphologically and perhaps in behavior and in community structure. Using desert rodent communities in the Great Basin Desert of U.S.A. and in the Negev Desert of Israel, I manipulated predatory risk in both communities and noted that foraging activity declines with increased predatory risk. Additional evidence suggests that predation also affects habitat selection behavior in both communities. Furthermore, differences in habitat utilization among species which promotes coexistence are related to morphological anti-predator specialization of the species. Predation appears to have shaped behavior and contributed to community structure in similar ways in both communities.

Yucca Mountain, Nevada is the proposed site for the underground storage of high-level civilian nuclear waste in the United States. The repository must be isolated from the general environment for at least 10,000 years. Ground water and gases are potential carriers of radioactive materials. Fractures and connected pores in the host rock are the major pathways for ground water and gases. Therefore, the mechanical and flow properties of the host rock should be understood and utilized in the design of the underground repository. Samples of Topopah Spring tuff from Yucca Mountain were used in this study. Cylindrical specimens were prepared to perform uniaxial and triaxial "damage" tests where specimens are loaded to a particular stress level to induce damage and fracturing and then unloaded. Mechanisms of microcracking at different fracturing levels have been studied by using both an optical microscope and a Scanning Electron Microscope (SEM). The original rock sample without loading was also observed under the microscopes. Many kinds of defects including pores, preexisting fractures, and soft inclusions were found in the undamaged Apache Leap tuff samples. Pores were determined to be the main microstructures in Topopah Spring tuff that could influence the mechanical and hydrologic properties. Under compressive stresses, microcracking initiates from some of the pores. These microcracks will interact and coalescence to form large microcracks or macroscopic cracks as the load is increased. Crack propagation phenomena, such as pore cracking, pore linking, pore collapse and the formation of en echelon arrays were all found in specimens unloaded prior to complete failure. The failure of tuff specimens is often through a process of shear localization. In summary, the deformation and failure of both tuffs occurred by progressive fracturing, starting from microcracking on the small scale, and ending as fractures coalesced to form macroscopic fractures and shear localization. On the basis of the experimental studies, micromechanical models such as the pore collapse model and the pore linking model have been developed based on fracture mechanics theory. These models are used to predict the constitutive behavior for tuff and the predicted stress-strain curves match well with the experimental curves.

This report is the third produced by the University of Wisconsin -Parkside's Applied Urban Field School research team regarding the potential effects on Indian cultural resources by the Intermountain Power Project electrical transmission lines. This report focuses on is concerned with the Native American cultural resources found within the revised section of the transmission line corridor.

This is the second of three reports produced for the Intermountain Power Project Native American cultural heritage resource study conducted by Richard Stoffle and members of the University of Wisconsin -Parkside Applied Urban Field School for Applied Conservation Technology, Inc. This report focuses on Southern Paiute cultural resources within the Nevada section of the Intermountain Power Project. This report analyzes what value members of Native American groups historically present in southern Nevada place upon cultural resources that may be adversely affected by construction of the proposed transmission line and associated structures. It does so by describing specific concerns expressed by contemporary Native Americans, and by presenting an ethnohistorical analysis of how intergroup relations and forced Native American demographic and cultural changes have contributed to shaping contemporary values, perceptions and attitudes. The project also conveys Native American recommendations for mitigating adverse impacts of the proposed construction upon their cultural heritage.

The overall objective of the American Indian study is the preparation of a written report focusing on the ethnohistory and contemporary perspectives of selected communities affected by the Old Spanish Trail (OST). The project can be divided into two separate but related parts: (1) a brief history of each community under study and its historic relationship to OST, and (2) a description of contemporary community views of the trail. Of special interest will be any contemporary knowledge related to the role played by the trail (and/or events related to the trail’s history and use) that affected the history and perspective of each community. Also of interest will be any places or resources along the trail that have significant cultural meaning to the subject communities. These are often referred to as “ethnographic resources.” This report describes American Indian responses to various activities along the OST during its pack-train period, which was roughly from 1829 to 1849. The Indian responses are diachronic beginning with the first contacts by Indian people residing on and using traditional Indian trails which were to be used for pack-trains to and from California and culminating decades later when the full impacts of pack-train use had been absorbed and responded to by these proximal Indian peoples. While there were contacts between Indian people and Euro-Americans before 1829, commercial traffic along the OST initiated unprecedented and sustained American Indian natural resource and social impacts. This report describes the places involved and responses received from American Indian tribal representatives during the field visits conducted from June 2006 to June 2007. This report helps both the American Indian tribes and the involved Federal agencies to better understand what kinds of responses have been recorded and what kinds of places have elicited these responses. The following tribes participated in this study: Chemehuevi Indian Tribe, Colorado River Indian Tribe, Las Vegas Paiute Tribe, Moapa Band of Paiute Indians, Pahrump Paiute Tribe, Paiute Indian Tribe of Utah, and Southern Indian tribe.

This is an American Indian ethnographic study for the Hoover Dam Bypass Project. The study sites included three bypass bridge alternatives, each located within one mile from where United States Highway 93 (U.S. 93), at the time of the study, crossed over the top of Hoover Dam at the Arizona-Nevada state line. Due to growth in population and commerce in the Southwest, the roadway at Hoover Dam has experienced a tremendous increase in traffic over the past 30 years, resulting in increased safety hazards to motorists, pedestrians, and the dam itself. Federal, state, and local governments have worked to find a solution to the impacts of increased traffic across Hoover Dam. This project was a continuation of EIS efforts that began in 1989. The goal of this project was to evaluate alternative crossings of the Colorado River near Hoover Dam. The goal of this study was to evaluate the potential impacts to American Indian cultural resources related to the three proposed crossing alternatives. This report is an expanded version of the draft produced in 1998. In 2000, funding became available to carry out further ethnographic research and involve Mohave, Hualapai, and Southern Paiute people.