Talk

Why does variability in chemostatic concentration-discharge relationships differ systematically between solutes in Antarctic streams?

Anonymous — Fri, 09 Apr 2021 22:02:07 +0000

Why does variability in chemostatic concentration-discharge relationships differ systematically between solutes in Antarctic streams? Anonymous (not verified) Fri, 04/09/2021 - 16:02 Joel Singley

Concentration-discharge (C-Q) relationships have been widely applied to infer integrated hydrologic and biogeochemical processes at the catchment-scale. Apart from event hysteresis or comparisons between catchments, relatively little attention has been given to the “noise” within long-term C-Q patterns. We analyze over two decades of historic data from 10 streams in the McMurdo Dry Valleys to assess systematic differences in chemostatic C-Q variability for solutes representing a continuum from weathering solutes to primary nutrients. We propose the hypothesis that variability in chemostasis can emerge from asynchronous variations in stream corridor source and sink processes. We present a theoretical test of this hypothesis using an alternative version of the OTIS model that allows for time-varying reaction kinetics. Our analysis demonstrates that (1) chemostasis of both weathering solutes and nutrients can emerge from stream corridor processes, (2) solutes governed by a larger number of coupled processes exhibit more chemostatic variability, and (3) temporal fluctuations in the net balance of source and sink process rates can explain these differences in variability. Our work ultimately highlights the potential to move beyond ignoring “noise” in long-term C-Q observations to better understand how the biogeochemical function of stream corridors varies over time.

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Improving Natural Water Quality through Wastewater Reuse

Anonymous — Fri, 09 Apr 2021 21:59:29 +0000

Improving Natural Water Quality through Wastewater Reuse Anonymous (not verified) Fri, 04/09/2021 - 15:59 Anthony Pimentel

Wastewater reuse is a growing application in many areas of the world as water scarcity is becoming a major issue due to climate change and exponential population growth. In Colorado, water reuse is becoming more viable because of drought and increased water demand. However, chemical contamination from industrial and domestic waste are a main concern of direct potable reuse project because of their ability to pass through conventional water treatment processes. Chemicals contaminants are well known to harm aquatic wildlife and can cause chronic illness if ingested at high concentrations. Membrane filtration can be applied in these settings to physically separate larger contaminants, but membrane fouling can reduce water quality and membrane lifetime. Advanced Oxidation Processes (AOPs) and ceramic membrane filtration can work together in water treatment processes to enhance chemical removal. This study investigated the synergistic effects of ceramic microfiltration and ozonation compared with other AOPs in secondary wastewater effluent. Ozone enabled oxidation of micropollutants, anthropogenic trace organic contaminants, were studied by measuring total organic carbon (TOC) and ultraviolet absorption (UVA254) reduction. Ozonation with ceramic microfiltration was compared to other AOPs such as UV with hydrogen peroxide (UV/H2O2) which can remove chemicals, pathogens, and bio foulants forming on the membrane surface. These bio foulants physically block membrane pores and lead to an increased transmembrane pressure (TMP) needed to push water through the membrane, as well as irreversible membrane fouling. Less membrane fouling leads to less frequent backwashing and chemical cleaning of the membranes, thus lowering operating costs and extending the lifetime of the membranes for water utilities. The study found that ozonation coupled with ceramic microfiltration was the most efficient in reducing TOC (~35-40%) and UVA254 (~60-70%). Overall, advancing technologies in wastewater reuse shows that potable reuse is becoming more viable and can enhance water availability while protecting natural water quality.

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Numerical Simulation of Partially Frozen Soils to Understand Aufeis Formation in Polar Regions

Anonymous — Fri, 09 Apr 2021 21:56:24 +0000

Numerical Simulation of Partially Frozen Soils to Understand Aufeis Formation in Polar Regions Anonymous (not verified) Fri, 04/09/2021 - 15:56 Alexi Lainis

Many hydrologic features in the polar regions will be impacted by increasing temperatures because of climate change. One of these such features is Aufeis (also known as Icings) which are large sheets of ice that form in river channels that can stay frozen well into summer. These features can be over 10 km2 in surface area and provide flow to rivers during the summer when other water resources are reduced (Pavelsky et al. 2017). The aim of this research is to better understand the processes that cause Aufeis to form, particularly the movement of groundwater below and near Aufeis fields. Specifically, we use SUTRA-ICE to analyze these groundwater conditions. Because these conditions include areas of permafrost and seasonally frozen soils, water is restricted and conveyed in complex patterns that can vary over time. Furthermore, the movement of subsurface water transports heat which then influences which areas are frozen or unfrozen. Terry et al. 2020 has come up with a conceptual model of these groundwater conditions using field data gathered from the Kuparuk Aufeis Field on the North Slope of Alaska. In this study we replicate this conceptual model using numerical simulations. So far, we have developed a 2-D model which shows a process by which subsurface water is forced to the surface by regions of frozen soils and regions of higher hydrologic conductivity during winter months. This water forced to the surface would then freeze contributing to Aufeis formation. Moving forward we will perform sensitivity analyses on this model with different soil hydraulic conductivities and different surface temperature forcings. By understanding the formation processes of Aufeis we will be able to predict how these hydrologic features might change because of rising temperatures and the potential impact to river ecosystems.

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Using fluorescence spectroscopy to detect photochemical changes of dissolved wildfire byproducts

Anonymous — Fri, 09 Apr 2021 20:31:46 +0000

Using fluorescence spectroscopy to detect photochemical changes of dissolved wildfire byproducts Anonymous (not verified) Fri, 04/09/2021 - 14:31 Jessie Egan

Nearly 80% of the United States’ freshwater originates in forested landscapes at risk of wildfires (United States Geological Survey (USGS), 2018), which influence both the terrestrial landscape and hydrologic regime by introducing a heterogeneous spectrum of thermally altered carbon compounds, known as pyrogenic carbon (PyC) (Bird et al., 2015). Given the projected increase in both wildfire frequency and intensity, understanding the coupling of hydrologic transport and chemical fractionation that wildfires impose on water sources is critical (Myers-Pigg et al., 2017). Research has begun to show that PyC can be quite mobile and reactive with turnover times of decades or years in soils rather than previously assumed millennia timescales, emphasizing the importance of dissolved PyC (DPyC) translocation from soils to rivers (Bird et al., 2015; Dittmar et al., 2012). While riverine PyC transport has been identified as a key component of the global PyC cycle, the extent to which photodegradation contributes to both short-term and long-term DPyC chemical fraction has yet to be resolved. We investigate the role of photodegradation as a major driver altering aquatic PyC physical and chemical properties. Artificial PyC was made by burning organic matter (leaves and soil) at various temperatures to isolate distinct portions of the PyC spectrum. Each temperature range of the PyC spectrum was separately leached, filtered, and the dissolved fraction was placed outside and exposed to natural sunlight for various exposure times ranging from zero to 28 days. This photodegradation experiment took place in Boulder, Colorado during the summer months to maximize daily sun exposure. Photochemistry was confirmed by monitoring the photochemical formation of hydrogen peroxide via fluorescence spectroscopy. The dissolved organic matter was primarily characterized using excitation-emission matrix (EEM) fluorescence spectroscopy. Our results confirm that 1) DPyC is susceptible to photodegradation, and 2) there are distinct fluorescence signatures and trends that can differentiate PyC from natural organic matter, underscoring that burn severity matters.

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Modeling the recent and future water and sediment discharge regime of the Ganges-Brahmaputra delta in response to a changing climate

Anonymous — Fri, 09 Apr 2021 20:29:12 +0000

Modeling the recent and future water and sediment discharge regime of the Ganges-Brahmaputra delta in response to a changing climate Anonymous (not verified) Fri, 04/09/2021 - 14:29 Abigail Eckland

The Ganges-Brahmaputra-Meghna (GBM) rivers carry a massive sediment load that feeds the world’s largest depositional system: the GBM megadelta. The mass of sediment transported annually by the GBM rivers has not been well constrained; previous estimates range between 0.5 and 2.4 BT/year. The present study attempts to resolve the sediment load of the GBM rivers to estimate their future sediment discharge regimes, a task of utmost importance for informing coastal management and predicting the sustainability of the GBM delta into the 21st century. A comprehensive modeling effort was conducted using HydroTrend, a well-established, climate-driven, water balance and sediment transport model. HydroTrend simulated daily water and sediment discharge from 1975 to 2100 at the Ganges and Brahmaputra basin outlets, driven by precipitation and temperature data spanning five global climate models (GFDL-ESM2M, HadGEM2, IPSL_CM5A, MIROC-ESM-CHEM, and NORESM-M) and three emission scenarios (reference, RCP4.5, and RCP8.5). The model was calibrated and validated using biweekly water discharge and suspended sediment concentration (SSC) data newly collected in 2019-2020, established sediment rating curves, and historic water discharge data over the reference scenario: 1975-2000. Results suggest HydroTrend simulates mean water discharge well, with percent errors of 2% and -7% for the Ganges and Brahmaputra rivers, respectively, over the reference scenario. The annual sediment load for the combined rivers was found to be on the low end of the previously estimated range (<1 BT/yr), determined from recently collected water discharge and SSC measurements. Simulations show that mean water and sediment discharge may increase by ~30% and ~50%, respectively, by end of century for the combined Ganges-Brahmaputra rivers. Refined sediment flux results will fuel macro-scale modeling efforts of GBM delta morphology, which will enhance our understanding of this complex deltaic system and can support the design of climate resilient adaptation measures.

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The Colorado River Basin Robustness Analysis web application: a novel tool for visualizing and filtering candidate Lake Mead operation policies

Anonymous — Fri, 09 Apr 2021 20:27:38 +0000

The Colorado River Basin Robustness Analysis web application: a novel tool for visualizing and filtering candidate Lake Mead operation policies Anonymous (not verified) Fri, 04/09/2021 - 14:27 Nathan Bonham

This presentation reveals the Colorado River Basin (CRB) Robustness Analysis web application. Robustness analysis is the process of simulating management alternatives in an ensemble of plausible future States of the World (SOW), then using statistical functions, called robustness metrics, to quantify the performance of each alternative when “stress-tested” in the SOW ensemble. In this research, we simulated 463 Lake Mead policies in 500 SOW each using the Colorado River Simulation System, where each SOW samples future scenarios of hydrology, Upper Basin demand, and initial reservoir pool elevations. Then, we calculated eight classes of robustness metrics and created an interactive visualization web application to visualize Lake Mead policies and filter them by robustness. This presentation provides an overview of the web application plus an example robustness analysis workflow to identify promising policies. This research includes several novel contributions: a web-application built on the philosophy of robustness metric exploration and efficient filtering of management alternatives, leveraging the non-domination operator as an alternative to aggregating metrics, and overall a framework for the Bureau of Reclamation and CRB stakeholders to assess robustness of Lake Mead policies. Authors: Nathan Bonham^1,2, Edith Zagona^1,2, Joseph Kasprzyk^{1,2 1}University of Colorado Boulder, department of Civil, Environmental, and Architectural Engineering ²Center for Advanced Decision Support for Water and Environmental Systems, University of Colorado Boulder.

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A Paleolimnological Analysis of Possum Kingdom Lake

Anonymous — Fri, 09 Apr 2021 20:26:34 +0000

A Paleolimnological Analysis of Possum Kingdom Lake Anonymous (not verified) Fri, 04/09/2021 - 14:26 Lane Allen

Reservoirs are typically considered too young and dynamic to validate paleolimnological analysis (Filstrup et al. 2010). Using biological and mineralogical proxies, three shifts were identified in the history of Possum Kingdom Lake, successfully demonstrating the application of paleolimnology in reservoirs. The trends documented may provide insight into the factors driving the P. parvum blooms that have been responsible for extensive economic losses.

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Inter- and intra-annual precipitation variability observed in the Navajo Nation

Anonymous — Fri, 09 Apr 2021 20:16:40 +0000

Inter- and intra-annual precipitation variability observed in the Navajo Nation Anonymous (not verified) Fri, 04/09/2021 - 14:16 Crystal Tulley-Cordova

The drought conditions in the Navajo Nation are severe to exceptional, and observed across the more than 70,000 square kilometers. The Navajo Nation is the largest land-based tribe in the United States that experiences impacts brought on by subtle changes in precipitation. Evaluation of precipitation from 2002 to 2015 water years across at 90 precipitation sites in Arizona, Utah, and New Mexico was completed. Five sub-regions of differing precipitation climatology were identified using k-means clustering, a vector quantization method. Spatial and temporal trends of precipitation variability were conducted with three climate indices and showed strong winter precipitation association to the Pacific North American teleconnection pattern for all regions; less correlation between climate indices and summer precipitation were observed; however, modest correlations with Pacific Decadal Oscillation were witnessed. Inter- and intra- annual precipitation variability contributes to additional climate change impacts observed.

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Snow in forest canopies: new insights from old ideas

Anonymous — Fri, 09 Apr 2021 20:15:29 +0000

Snow in forest canopies: new insights from old ideas Anonymous (not verified) Fri, 04/09/2021 - 14:15 Mark Raleigh

In forested basins, the amount of snow that accumulates on the ground depends on how much snowfall is intercepted in the forest canopy and the subsequent partitioning of canopy snow into sublimation, unloading, and melt drip. However, the amount of precipitation intercepted in forest canopies is rarely measured, and existing field studies of snow interception have suggested opposing sensitivities to temperature. Reliable observational techniques of canopy interception are needed to advance understanding and management of forested watersheds, especially in the context of a changing climate. Nearly five decades ago, a field study noted that wind-induced tree sway decreased when the canopy was loaded with snow, but to date this promising method has not been applied to measure snow interception. Here, I detail my efforts to use this technique to quantify the mass of intercepted snowfall in coniferous canopies. Accelerometers collected tree sway data nearly-continuously for six years at Niwot Ridge (2014-2020, two trees), and one year each at Grand Mesa (2016-2017, three trees) and Senator Beck Basin (2016-2017, two trees) in Colorado. Consistent with mechanical theory, the data show coherent drops in tree sway frequency during snow interception events, but also show increases in frequency when the trees freeze and become rigid. Compared to ground-based measurements of new snow, the sway technique shows good correspondence in the relative magnitude of snowstorms and a reasonable representation of the maximum snow interception capacity of a canopy. I will highlight the opportunities and limitations of this methodology for refining understanding of canopy processes in models.

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Projected large-scale regional baseflow declines in response to changing climate in the Upper Colorado River Basin

Anonymous — Fri, 09 Apr 2021 20:10:59 +0000

Projected large-scale regional baseflow declines in response to changing climate in the Upper Colorado River Basin Anonymous (not verified) Fri, 04/09/2021 - 14:10 Matt Miller

Given the importance of groundwater in sustaining Upper Colorado River Basin (UCRB) streamflow (over 50% of streamflow originates as baseflow), effective management of water resources in the basin requires estimates of how baseflow may change under projected climatic changes. We applied projections of future climate to a calibrated hybrid statistical-deterministic model (SPAtially Referenced Regressions On Watershed attributes, SPARROW) to estimate future baseflow changes under warm/wet, hot/dry, and central tendency climatic conditions for thirty-year periods centered around 2030, 2050, and 2080 compared to the historical period (1984-2012). Projected widespread baseflow declines, regardless of changes in precipitation, suggest increased evapotranspiration reduced baseflow. The largest relative declines in baseflow are projected to occur in high elevation source areas, and baseflow delivered to the UCRB outlet declining by between 11% and 40%. Results have implications for human and ecological water availability in one of the most heavily managed watersheds in the world.

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