Nitrate removal along a Colorado montane headwater stream: the role of bidirectional hydrologic exchange at reach to catchment scales

Includes bibliographical references.2015 Fall.Bidirectional hydrologic exchanges between surface water and groundwater along a stream reach can act to dilute nutrient levels (physical processes), and/or can facilitate biogeochemical cycling (physical and biological processes). Such exchanges thus affect nitrogen transport within stream catchments, many of which have been altered in high-elevation locations along Colorado's Front Range due to elevated nitrogen levels from industrialization in recent decades. We applied a fully informed hydrologic mass balance model and nitrate mass balance model that include gross gains and gross losses along a 1000 m study reach, to better understand nitrate removal potential for a Colorado montane zone catchment, Lower Gordon Gulch. We collected data during four synoptic stream tracer and sampling campaigns along our study reach during the 2014-2015 water year, and also analyzed near-stream riparian lateral hydraulic gradients to assess groundwater and surface water interactions from a second perspective. Three distinct hydrologic regimes are captured in our results, including two experiments during baseflow, one experiment following snowmelt, and one experiment following late-spring rainfall. Results show a transition from hydrologic sources of nitrate following snowmelt, to biological sources during rainfall, and finally to hydrologic removal during baseflow. Higher hillslope water content appears to be directly correlated with nitrate sources, and lower in-stream discharge appears to be directly correlated with in-stream nitrate removal. This finding combined with lateral hydraulic gradient results point to groundwater-surface water interactions. Our findings corroborate earlier work in montane zone streams that show preferential flow on south-facing slopes and matrix flow with greater microbial activity on north-facing slopes following snowmelt. We provide a modeling framework that separates physical from biological processes to assess the potential of such catchments to cycle nitrate, which can help scientists and environmental planners in assessing ecosystem changes in Colorado due to anthropogenic influences

Simulations of an observed elevated mesoscale convective system over southern England during CSIP IOP 3

Simulations of an elevated mesoscale convective system (MCS) observed over southern England during the Convective Storm Initiation Project (CSIP) provide the first detailed modelling study of a case of elevated convection occurring in the UK. The study shows that many factors can influence the maintenance of elevated deep convection, from large-scale flow through to surface heating processes and diabatic cooling within the convective system. It is also shown that interactions and feedback mechanisms between a stable layer and the storm can act to maintain deep convection. The simulation successfully reproduced an elevated MCS above a low-level stable undercurrent, with a wave in the undercurrent linked to a rear-inflow jet (RIJ). Convection was fed from an elevated (840hPa) source layer with CAPE of about 350Jkg-1. The undercurrent in the simulation was approximately 1km deep, about half that observed. Unlike the observed MCS, a transition from elevated to surface-based convection occurred in the simulation due to the combined effects of a pre-existing large-scale θe gradient, advection and surface heating causing the system to encounter increasingly unstable low-level air and a shallower stable layer that was more susceptible to penetration by downdraughts. The transition to surface-based convection was accompanied by the development of cold-pool outflow and an increase in system velocity from about 6 to 10ms-1. Diabatic cooling from microphysical processes in the simulation enhanced the undercurrent and strengthened the RIJ. This strengthened the wave in the undercurrent and led to more extensive convection. The existence of a positive feedback process between the convection, RIJ and stable layer is discussed. Uncertainty in the synoptic scale generating errors in the undercurrent is shown to be a major source of error for convective-scale forecasts

Multi-family urban housing

Typescript (photocopy)

Control-Motion Studies of the PBM-3 Flying Boat in Abrupt Pull-Ups

No abstract availabl

The relationship between economic and political performance in Italy, 1948-1977

Thesis (B.A.) in Political Science -- University of Illinois at Urbana-Champaign, 1988.Bibliography: leaves 34-36.Microfiche of typescript. [Urbana, Ill.]: Photographic Services, University of Illinois, U of I Library, [1988]. 2 microfiches (43 frames): negative

Ohio Northern Alumnus - October, 1927

https://digitalcommons.onu.edu/alumni_mag/1002/thumbnail.jp

The reconciliation of communicative competence and structuralist approaches to second language acquisition: An account of my teaching approach experimentation

Thesis (B.A.) in French -- University of Illinois at Urbana-Champaign, 1990.Includes bibliographical references (leaf 21)Microfiche of typescript. [Urbana, Ill.]: Photographic Services, University of Illinois, U of I Library, [1990]. 1 microfiche (25 frames): negative.s 1990 ilu n

Climate Change, Snow Mold and the Bromus tectorum Invasion: Mixed Evidence for Release from Cold Weather Pathogens

Climate change is reducing the depth and duration of winter snowpack, leading to dramatic changes in the soil environment with potentially important ecological consequences. Previous experiments in the Intermountain West of North America indicated that loss of snowpack increases survival and population growth rates of the invasive annual grass Bromus tectorum; however, the underlying mechanism is unknown. We hypothesized that reduced snowpack might promote B. tectorum population growth by decreasing damage from snow molds, a group of subnivean fungal pathogens. To test this hypothesis, we conducted greenhouse and field experiments to investigate the interaction between early snowmelt and either fungicide addition or snow mold infection of B. tectorum. The greenhouse experiment confirmed that the snow mold Microdochium nivale can cause mortality of B. tectorum seedlings. In the field experiment, early snowmelt and fungicide application both increased B. tectorum survival, but their effects did not interact, and snow mold inoculation had no effect on survival. We did find interactive effects of snowmelt and fungal treatments on B. tectorum seed production: with ambient snowpack, M. nivale inoculation reduced seed production and fungicide increased it, whereas in the early snowmelt treatment seed production was high regardless of fungal treatment. However, treatment effects on seed production did not translate directly to overall population growth, which did not respond to the snow melt by fungal treatment interaction. Based on our mixed results, the hypothesis that reduced snowpack may increase B. tectorum fitness by limiting the effects of plant pathogens deserves further investigation