Climate-driven Shifts in Quantity and Seasonality of River Discharge over the past 1000 Years from the Hydrographic Apex of North America

Runoff generated from high elevations is the primary source of freshwater for western North America, yet this critical resource is managed on the basis of short instrumental records that capture an insufficient range of climatic conditions. Here we probe the effects of climate change over the past ~1000 years on river discharge in the upper Mackenzie River system based on paleoenvironmental information from the Peace-Athabasca Delta. The delta landscape responds to hydroclimatic changes with marked variability, while Lake Athabasca level appears to directly monitor overall water availability. The latter fluctuated systematically over the past millennium, with the highest levels occurring in concert with maximum glacier extent during the Little Ice Age, and the lowest during the 11th century, prior to medieval glacier expansion. Recent climate-driven hydrological change appears to be on a trajectory to even lower levels as high-elevation snow and glacier meltwater contributions both continue to decline

Characterizing the Hydrology of Shallow Floodplain Lakes in the Slave River Delta, NWT, Canada, Using Water Isotope Tracers

The relative importance of major hydrological processes on thaw season 2003 lakewater balances in the Slave River Delta, NWT, Canada, is characterized using water isotope tracers and total suspended sediment (TSS) analyses. A suite of 41 lakes from three previously recognized biogeographical zones—outer delta, mid-delta, and apex—were sampled immediately following the spring melt, during summer, and in the fall of 2003. Oxygen and hydrogen isotope compositions were evaluated in the context of an isotopic framework calculated from 2003 hydroclimatic data. Our analysis reveals that flooding from the Slave River and Great Slave Lake dominated early spring lakewater balances in outer and most mid-delta lakes, as also indicated by elevated TSS concentrations (\u3e0.01 g L-1). In contrast, the input of snowmelt was strongest on all apex and some mid-delta lakes. After the spring melt, all delta lakes underwent heavy-isotope enrichment due to evaporation, although lakes flooded by the Slave River and Great Slave Lake during the spring freshet continued to be more depleted isotopically than those dominated by snowmelt input. The isotopic signatures of lakes with direct connections to the Slave River or Great Slave Lake varied throughout the season in response to the nature of the connection. Our findings provide the basis for identifying three groups of lakes based on the major factors that control their water balances: (1) flood-dominated (n=10), (2) evaporation-dominated (n=25), and (3) exchange-dominated (n=6) lakes. Differentiation of the hydrological processes that influence Slave River Delta lakewater balances is essential for ongoing hydroecological and paleohydrological studies, and ultimately, for teasing apart the relative influences of variations in local climate and Slave River hydrology

Computational techniques for the assessment of fracture repair

The combination of high-resolution three-dimensional medical imaging, increased computing power, and modern computational methods provide unprecedented capabilities for assessing the repair and healing of fractured bone. Fracture healing is a natural process that restores the mechanical integrity of bone and is greatly influenced by the prevailing mechanical environment. Mechanobiological theories have been proposed to provide greater insight into the relationships between mechanics (stress and strain) and biology. Computational approaches for modelling these relationships have evolved from simple tools to analyze fracture healing at a single point in time to current models that capture complex biological events such as angiogenesis, stochasticity in cellular activities, and cell-phenotype specific activities. The predictive capacity of these models has been established using corroborating physical experiments. For clinical application, mechanobiological models accounting for patient-to-patient variability hold the potential to predict fracture healing and thereby help clinicians to customize treatment. Advanced imaging tools permit patient-specific geometries to be used in such models. Refining the models to study the strain fields within a fracture gap and adapting the models for case-specific simulation may provide more accurate examination of the relationship between strain and fracture healing in actual patients. Medical imaging systems have significantly advanced the capability for less invasive visualization of injured musculoskeletal tissues, but all too often the consideration of these rich datasets has stopped at the level of subjective observation. Computational image analysis methods have not yet been applied to study fracture healing, but two comparable challenges which have been addressed in this general area are the evaluation of fracture severity and of fracture-associated soft tissue injury. CT-based methodologies developed to assess and quantify these factors are described and results presented to show the potential of these analysis methods

Factors Which Affect Furrow Intake Rates

To apply irrigation water efficiently, the water must be absorbed evenly across the field. In surface irrigation systems, this requires either that the water be spread quickly across the soil surface so that each portion of the field has a nearly equal time to absorb water, and that all portions of the field absorb water at the same rate; or that water intake rate varies across the field to compensate for differences in intake opportunity time. Water distribution in surface irrigation systems is determined by: 1) the water application system capabilities and management, and 2) the infiltration characteristics of the field soils. Improved application systems and design procedures for surface irrigation are being developed. But unless soil infiltration rates can be managed to achieve uniform water intake at desireable rates, high surface irrigation application efficiencies cannot be achieved. Although the problem of nonuniform soil water intake can be solved by applying the water through sprinkler or trickle systems at rates lower than the lowest intake rates, with the present high energy costs, this option is often not economical. The objective of this study is to evaluate several farmer manageable factors which can affect water intake rates into irrigated furrows. The long term research goal is to quantify the effects of farmer practices which decrease intake uniformity, practices he can apply to improve uniformity, and practices which can change intake rates. Intake rate modification can be useful to accelerate advance (thus decreasing variations in intake opportunity times), counteract the effects of variations in intake opportunity times, or better - adapt a field to a fixed or desireable water application system or schedule. The manageable factors which will be discussed are: 1) wheel compaction of furrows 2) surface soil water content 3) flow rates, and 4) intermittent application, such as "surge" irrigation

Brane Localized Curvature for Warped Gravitons

We study the effects of including brane localized curvature terms in the Randall-Sundrum (RS) model of the hierarchy. This leads to the existence of brane localized kinetic terms for the graviton. Such terms can be induced by brane and bulk quantum effects as well as Higgs-curvature mixing on the brane. We derive the modified spectrum of Kaluza-Klein (KK) gravitons and their couplings to 4-dimensional fields in the presence of these terms. We find that the masses and couplings of the KK gravitons have considerable dependence on the size of the brane localized terms; the weak-scale phenomenology of the model is consequently modified . In particular, the weak-scale spin-2 graviton resonances which generically appear in the RS model may be significantly lighter than previously assumed. However, they may avoid detection as their widths may be too narrow to be observable at colliders. In the contact interaction limit, for a certain range of parameters, the experimental reach for the scale of the theory is independent of the size of the boundary terms.Comment: 20 pages, 11 figures, LaTex, minor revision

Cablegation: A review of the past decade and prospects for the next

Cablegation is an automated surface irrigation application system (Kemper et al., 1987). It was conceived and first tested in 1980 by USDA-Agricultural Research Service scientists at Kimberly, Idaho (Kemper et al., 1981). Over the past ten years, cablegation has been adapted to a wide range of conditions and a variety of commercially-available components have been developed. Over 100 systems have been installed on farmers' fields in 9 western states. The potential labor and water savings have been demonstrated. After initial widespread interest and rapid growth, the rate of system installation has declined and about 40% of the installations are no longer being used as designed. The objective of this paper is to describe the reasons for the reduced growth and to project the adoption of the technology for the coming decade. Many of the motivations and constraints discussed are common to other automated surface irrigation systems

Earthworms cause furrow infiltration increase

Infiltration rates into furrows in Southern Idaho, after decreasing toward a base rate, often increase. The increase is caused by earthworms piercing the furrow wetted perimeter during the irrigation and water entering and infiltrating from their interconnected burrow systems

Shifts in the Properties of the Higgs Boson from Radion Mixing

We examine how mixing between the Standard Model Higgs boson, $h$, and the radion present in the Randall-Sundrum model of localized gravity modifies the expected properties of the Higgs boson. In particular, we demonstrate that the total and partial decay widths of the Higgs, as well as the $h\to gg$ branching fraction, can be substantially altered from their Standard Model expectations. The remaining branching fractions are modified less than \lsim 5% for most of the parameter space volume.Comment: 17 pages, 7 figs., LaTex; revised versio

Watercourse Improvement in Pakistan

Extensive conveyance loss measurements in watercourses in the Pakistan Indus Basin indicated water loss in the range of 30 to 50 per cent of the inflow. This high loss motivated the development and testing of several system improvements which could be grouped in the categories of improved maintenance, redesign and earthen reconstruction, and channel lining. Evaluation of the costs and water savings of these techniques allowed the formulation of an optimal watercourse improvement strategy. This improvement strategy, which increases water deliveries to the field by 30 per cent, is presently being applied on a large scale by the Pakistan On-Farm Water Management Project. Total farmer provision of labor is evidence of their support for the program and recognition of its benefits