Applications of lead and strontium isotope analysis were made on archaeological materials from three different contexts in both the Old and New Worlds. These materials comprised pre-Hispanic glaze painted ceramics from Arizona, U.S.A., glass beads from late first millennium AD Igbo-Ukwu, Nigeria, and copper-based metals from early first millennium AD Kissi, Burkina Faso. All materials contain lead at major, minor, or trace concentrations, and lead isotope analysis was employed to determine a provenance for that lead. Strontium isotope analysis also was applied to glass beads from Igbo-Ukwu to determine provenance(s) for strontium found in the glass. Furthermore, application of elemental composition analysis was or had been employed on all samples for additional data comparisons within assemblages and with comparable archaeological materials.Results of these analyses determined, in most cases, regional provenance with high degrees of confidence for lead contained in the analyzed samples. Strontium and elemental composition analysis data also proved valuable in confirming the regional provenance of the raw glass used to produce the glass beads. Leads in the glaze paints from Arizona, which demonstrated a range of resources exploitation, were confidently restricted to a few regions for their procurement. Likewise leads in most glass beads from Igbo-Ukwu were confidently restricted to two main source regions, with a third strong contender also being identified. The elemental composition and strontium isotope data determined with confidence the production regions for the primary raw glasses used to make the glass beads. Finally, leads in copper-based metals from Burkina Faso also were restricted to a few regions, although some inconclusiveness in provenance determination was attributed to mixing of metals from difference sources.These results confirm the utility of heavy isotope analysis of archaeological materials for provenance determination. The combination of these data with elemental composition analyses further confirm the interpretive strength of combining independent but related sets of analytical data for exploring questions of archaeological provenance. With improvements in instrument technology and application in the past two decades, very high precision and high accuracy analyses can be made which eliminate some earlier concerns of heavy isotope applications in archaeology.

abstract: Biological soil crusts (BSCs) dominate the soil surface of drylands in the western United States and possess properties thought to influence local hydrology. Little agreement exists, however, on the effects of BSCs on runoff, infiltration, and evaporative rates. This study aims to improve the predictive capability of an ecohydrology model in order to understand how BSCs affect the storage, retention, and infiltration of water into soils characteristic of the Colorado Plateau. A set of soil moisture measurements obtained at a climate manipulation experiment near Moab, Utah, are used for model development and testing. Over five years, different rainfall treatments over experimental plots resulted in the development of BSC cover with different properties that influence soil moisture differently. This study used numerical simulations to isolate the relative roles of different BSC properties on the hydrologic response at the plot-scale. On-site meteorological, soil texture and vegetation property datasets are utilized as inputs into a ecohydrology model, modified to include local processes: (1) temperature-dependent precipitation partitioning, snow accumulation and melt, (2) seasonally-variable potential evapotranspiration, (3) plant species-specific transpiration factors, and (4) a new module to account for the water balance of the BSC. Soil, BSC and vegetation parameters were determined from field measurements or through model calibration to the soil moisture observations using the Shuffled Complex Evolution algorithm. Model performance is assessed against five years of soil moisture measurements at each experimental site, representing a wide range of crust cover properties. Simulation experiments were then carried out using the calibrated ecohydrology model in which BSC parameters were varied according to the level of development of the BSC, as represented by the BSC roughness. These results indicate that BSCs act to both buffer against evaporative soil moisture losses by enhancing BSC moisture evaporation and significantly alter the rates of soil water infiltration by reducing moisture storage and increasing conductivity in the BSC. The simulation results for soil water infiltration, storage and retention across a wide range of meteorological events help explain the conflicting hydrologic outcomes present in the literature on BSCs. In addition, identifying how BSCs mediate infiltration and evaporation processes has implications for dryland ecosystem function in the western United States. / Dissertation/Thesis / Masters Thesis Geological Sciences 2015

An evaluation for Lag time, defined as the time from the centroid of rainfall excess to the centroid of direct runoff, was performed for seven small watersheds in the Southwestern United States. The size of these watersheds range in size from 0.33 to 4.37 ha. The evaluation period goes from 2000 to 2010. This evaluation was compared versus 28 lag time equations.The USDA-ARS Southwest Watershed Research Center has developed an electronic data processing system where rainfall and runoff data is collected from sensors in the field and are transmitted to computers in the office.Prior to these data sets there were no measurable rainfall and runoff data. This digital data is generated by means of synchronized clocks in rain gages and flumes. As a result, the data from this electronic processing system offers a unique opportunity for hydrologic research. This infrastructure is a characteristic not often available in many other sites and a condition not enjoyed in previous investigations.There are several definitions of lag time depending on what particular time period is used to describe the occurrence of unit rainfall and runoff. But, time parameters currently lack commonly-accepted standard definitions.The various definitions for time parameters such as Lag Time, Time of Concentration, Time to Peak, Equilibrium Time and others, sometimes, are used interchangeably. Another aspect is that in Lag time determination, centers of mass play a critical role. This study found out that depending of the loss model chosen to estimate rainfall excess, it shall influence the determination of center of mass and hence the lag time.Some negative values were obtained for lag time when measured from peak of runoff to centroid of effective rainfall. However, in the lag time definition from centroid of effective rainfall to centroid of direct runoff, negative values were not obtained.One field in particular, time parameters currently lacks commonly-accepted standard definitions. This has become a source of profound confusion in this branch of science to the point where teams of scientists writing about and discussing hydrological Time Parameters can be compared to the aftermath at the Tower of Babel.