Browsing by Author "Ross, Matthew, committee member"
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Item Open Access A characterization of Colorado Front Range and Denver basin aquifer system water stable isotope signatures(Colorado State University. Libraries, 2024) Ulate, Isabella, author; Rugenstein, Jeremy K. C., advisor; Ronayne, Michael, committee member; Ross, Matthew, committee memberThe Denver Basin Aquifer System (DBAS) is an important groundwater resource for Front Range communities and is currently experiencing increasing demand as populations grow and surface water supplies remain limited. It is necessary to better constrain aquifer recharge mechanisms to enable sustainable use of this resource. In other sedimentary basin aquifer systems, mountain front recharge has been shown to be a significant contributor to local basin groundwater recharge. In the DBAS, inputs from the mountain block are poorly understood, and previous numerical models have treated large segments of the mountain-front boundary as impermeable. However, there exist potential connections between the mountain block and the DBAS, either by direct contact of permeable units, which would facilitate underflow recharge into the basin, or by surface water infiltration to the aquifer units where they outcrop near the mountain front. To observe spatial and temporal relationships between mountain block water and DBAS water, we use water stable isotopes and characterize the δ2H and δ18O of monthly precipitation, seasonal surface waters, and groundwaters in and around the Front Range and Denver Basin. The goal of this study is to determine if differences in the isotopic composition of waters across the Front Range permit the use of δ18O and δ2H as tracers of water flow between Front Range streams and groundwater and the DBAS. We analyzed the unique signature of mountain-block water to compare with DBAS water stable isotope data collected from Castle Rock Water municipal wells. Stable isotope ratios varied spatially and temporally, with the greatest temporal variance observed in precipitation. Streams showed great spatial variance, and less significant seasonal variance between the three seasonal sampling events conducted. Groundwaters showed very little temporal variance but had great spatial variance both between the aquifer units of the DBAS and between different locations within the mountain block crystalline aquifer. The lowest δ2H and δ18O ratios were measured in winter precipitation, winter streams, and groundwater samples collected from the high-elevation Front Range. Samples of DBAS groundwaters with the lowest δ2H and δ18O ratios indicate potential hydrogeologic connection to the mountain block. Interpreted mixing lines on a d-excess versus δ18O plot support the potential DBAS-mountain block connection. The deepest aquifer units of the DBAS (Arapahoe and Laramie-Fox Hills) show the least relationship with meteoric or surface waters on both a δ2H and δ18O plot and the d-excess versus δ18O plot and have higher δ18O values than would be predicted based on their previously measured recharge ages and paleoclimate data from the region. Characterizing the spatial and temporal variations in water stable isotope signatures of the Front Range and DBAS region enhances understanding of the region's hydrology and hydrogeology. Additionally, these results help to better inform models of aquifer recharge and promote sustainable use of the DBAS resource.Item Open Access Acid mine drainage impacts in the Upper Arkansas River Basin: a study of water quality, treatment efficiency, and predicted longevity(Colorado State University. Libraries, 2019) Moore, Megan, author; Covino, Tim, advisor; Ross, Matthew, committee member; Wilkins, Mike, committee member; Rhoades, Charles, committee memberMining activity in the Sugarloaf and Leadville mining districts of Leadville, Colorado has impaired water quality in the Upper Arkansas River Basin. Tributary and main channel waters are often out of compliance with state water quality standards, and stream flora and fauna as well as human use of these waterways is threatened by acid mine drainage. This study aims to describe the impact historical mining activity has had on the waters of the Upper Arkansas River Basin by characterizing water quality, analyzing metal removal efficiency from both active and passive treatment sites in the area, and estimating the time it will take for drainage from mining tunnels to naturally comply with state water quality standards. A comparison of instream dissolved concentrations of cadmium, copper, iron, lead, manganese, and zinc to state water quality standards shows waters of the Upper Arkansas River Basin are often out of compliance with chronic and/or acute standards. This is seen more frequently upstream from treatment sites and higher up in the tributary system than at tributary mouths or in the main channel of the Arkansas River. An examination of metal removal from the Leadville Mine Drainage Tunnel and Yak Tunnel water treatment plants along East Fork and California Gulch shows dissolved metal reduction between 33 and 100 percent compared with 0 to 84 percent at the passive Dinero Wetland Complex along Lake Fork. Finally, an analysis of projected longevity highlights the importance of clean-up plans for future mining projects with estimated impaired water quality continuing upwards of 2000 years at Yak Tunnel.Item Open Access Changes in water chemistry and fluvial geomorphology from arsenic contaminated floodplains of Whitewood Creek and Belle Fourche River, South Dakota(Colorado State University. Libraries, 2023) Marr, Alexander E., author; Sutton, Sally, advisor; Ridley, John, advisor; Ross, Matthew, committee memberFrom 1877 to 1977 the Homestake Gold Mine in Lead, South Dakota released over 100 million megagrams (Mg) of arsenic rich mine waste into Whitewood Creek which joins the Belle Fourche River. The mine waste which contains arsenopyrite and other arsenic bearing minerals, is deposited along the floodplains of Whitewood Creek and the Belle Fourche River as overbank deposits and abandoned meander and channel fill. The introduction of mine tailings into these streams has impacted them chemically and geomorphologically for over 100 years. This study is a continuation of the work from Ji (2021) who focused on the long-term behavior of arsenic in the mine tailings. Her work involved sequential extractions of the tailings to determine the mineralogical setting of the arsenic and its rate of release. She also used statistical regression on historical data to estimate the physical and chemical removal of arsenic from Whitewood Creek's watershed. The focus of this study is to see how the tailings might have impacted the stream chemistry of Whitewood Creek and the Belle Fourche River by modeling mineral saturation indices of the stream and seep water through the geochemical modeling program, The Geochemist's Workbench. The Geochemist's Workbench was used to model the dissolution rate of arsenopyrite to calculate the rate of dissolved arsenic entering Whitewood Creek. Suspended arsenic entering Whitewood Creek was calculated using the dimensions of the creek bed, thickness of tailings, and density of arsenopyrite. In addition to chemistry, this study investigated the changes in the tailings and fluvial geomorphology of Whitewood Creek and the Belle Fourche River from 1948 to 2012. This was performed by using aerial photographs from 1971, which mapped locations of the tailings along the floodplains, and overlaying them with photographs from 1948, 1977, and 2012. Using GIS through ArcMap, the tailings and their portions that have been removed over time were digitized. Other fluvial parameters that have been determined and digitized are stream longitudinal profiles, sinuosity, contaminated floodplain width, channel migration, and total sediment deposition area. The mineral saturation indices of Whitewood Creek and the Belle Fourche River are similar to each other and differ at the most by around 2-3 orders of magnitude. The minerals that are supersaturated are mainly phyllosilicates (mostly clays), Fe, Cu and Al (hydr)oxides, and carbonates with minor sulfates and phosphates. Seep waters have lower mineral saturation indices, up to 10 orders of magnitude lower for Fe bearing minerals. The only arsenic bearing mineral that is calculated to be supersaturated is Ba3(AsO4)2; however, this mineral has not been observed in nature. Based on the range of possible arsenopyrite concentration in the contaminated sediment (15 to 0.11%), the calculation of dissolved arsenic being discharged out of Whitewood Creek ranges from 52 to 0.39 Mg per year. This range compares to Ji's (2021) daily dissolved arsenic rate range of 3.89-0.33 Mg/year. For a tailings width range of 0.6 to 3.5 m, the calculated rate of suspended arsenic being discharged ranges from 254 to 1.98 Mg per year. Although large, this range encompasses Ji's (2021) suspended arsenic transport rate range of 33 to 70 Mg per year. The overlap of values from Ji's (2021) statistical approach and this study's geochemical approach indicates that arsenopyrite may be to some degree significant in controlling As transportation in Whitewood Creek. Based on GIS results, the location and evolution of contaminated floodplains along Whitewood Creek and the Belle Fourche River are very complex. The streams are different from each other and behave as their own systems. In Whitewood Creek, locations with high tailings area and removal are controlled by a possible range of factors such as knickzone geomorphology, bedrock lithology, and changes in stream energy due to topography. In the Belle Fourche River, reaches with high tailings area and removal are found about 7 km from the Whitewood Creek confluence and a 30 km stretch where rapid floodplain reworking occurs due to neotectonics from Precambrian basement adjustments. Tailings removed area and contaminated floodplain width graphs show that the Belle Fourche River has larger storage for tailings and undergoes more floodplain reworking due to higher flood frequency and neotectonics. In contrast, Whitewood Creek has lower storage and erosion due to decreasing mine sediment load at least since 1948 and channel incision into shale bedrock in some reaches. While the reworking of tailings into the stream is lower in Whitewood Creek than the Belle Fourche River, the tailings will remain on the floodplains for many generations.Item Open Access Errors of opportunity: using neural networks to predict errors in the unified forecast system (UFS) on S2S timescales(Colorado State University. Libraries, 2023) Cahill, Jack, author; Barnes, Elizabeth A., advisor; Maloney, Eric D., advisor; Ross, Matthew, committee memberMaking predictions of impactful weather on timescales of weeks to months (subseasonal to seasonal; S2S) in advance is incredibly challenging. Dynamical models often struggle to simulate tropical systems that evolve over multiple weeks such as the Madden Julian Oscillation (MJO) and the Boreal Summer Intraseasonal Oscillation (BSISO), and these errors can impact geopotential heights, precipitation, and other variables in the continental United States through teleconnections. While many data-driven S2S studies attempt to predict future midlatitude variables using current conditions, here we instead focus on post-processing of the National Oceanic and Atmospheric Association's (NOAA) Unified Forecast System (UFS) to predict UFS errors. Specifically, by looking at when/where there are errors in the UFS, neural networks can be used to understand what atmospheric conditions helped produce these errors via explainability methods. Our 'Errors of Opportunity' approach identifies phase 4 of the MJO and phases 1 and 2 of the BSISO as significant factors in aiding UFS error prediction across different regions and seasons. Specifically, we see high accuracy for underestimates of geopotential heights in the Pacific Northwest during Spring and as well as high accuracy for overestimates of geopotential heights in Northwest Mexico during Summer. Furthermore, we demonstrate enhanced error prediction skill for overestimates of Summer precipitation in the Midwest following BSISO phases 1 and 2. Most notably, our findings highlight that the identified errors stem from the UFS's failure to accurately forecast teleconnection patterns.Item Open Access Exploration of passive desaturation of in place tailings using wicking geosynthetics(Colorado State University. Libraries, 2024) Monley, Kendall O., author; Scalia, Joseph, IV, advisor; Bareither, Christopher, committee member; Ross, Matthew, committee memberAs global demand for metals and critical minerals increases, so too does the production of tailings. Tailings are what is left behind after extraction of valuable metals and minerals from ore, and consist of finely ground rock, water, unrecoverable metals, chemicals, and organic matter. These residuals are managed in engineered facilities that function to both dewater and store tailings, known as tailings storage facilities (TSF). A common assumption is that the water initially contained in TSFs will drain down to an unsaturated condition after deposition of new tailings ceases. However, a review of literature on geotechnical and hydrotechnical conditions of legacy TSFs (TSFs that have stopped receiving tailings) in arid environments illustrates that achievement of unsaturated conditions in internal fine-grained layers may not always occur. As the tailings are deposited, layers of finer and coarser particles are interbedded. This causes the formation of capillary barriers and may ultimately result in finer-grained layers held at near saturation after drain down. These fine-grained layers are more susceptible to liquefaction concerns and can require costly remedial actions to ensure geotechnical stability. Dewatering is the process of removing water from whole tailings and offers benefits including increasing geotechnical stability and recovering stored water. Tailings dewatering may occur prior to or after deposition into a TSF. In this study, I explore in-situ dewatering via use of capillary (wicking) geotextiles, and the effectiveness of the wicking geotextiles. Beaker and column experiments were created to emulate stratigraphy seen in legacy TSFs. Additionally, shrinkage testing was conducted to compare the final densities and void ratios of samples with and without wicking geotextiles. Column testing reveals the wicking geotextiles accelerated dewatering by 2.8 times the rate of natural drying processes. At the conclusion of testing, the wicking geotextile experiments had reached similar densities and void ratios to control experiments. This novel approach to passively dewatering tailings warrants additional testing.Item Open Access Managing developing landscapes for stormwater, water yield, and ecosystem services with data-driven approaches(Colorado State University. Libraries, 2022) Choat, Benjamin, author; Bhaskar, Aditi, advisor; Sharvelle, Sybil, committee member; Kampf, Stephanie, committee member; Ross, Matthew, committee memberTo view the abstract, please see the full text of the document.Item Open Access Metagenomic insights into microbial colonization & persistence in subsurface fractured shales(Colorado State University. Libraries, 2023) Amundson, Kaela K., author; Wilkins, Michael J., advisor; Wrighton, Kelly C., committee member; Borch, Thomas, committee member; Ross, Matthew, committee memberMicroorganisms are pervasive yet important components of hydraulically fractured shale systems. Subsurface shales harbor oil & gas and require unconventional techniques, such as hydraulic fracturing, to access these trapped hydrocarbons. Shale microbiomes are of crucial importance as they can directly impact the recovery of oil & gas and associated infrastructure. The overarching theme of this dissertation was to characterize the metabolisms and key traits that underpin the colonization and persistence of fractured shale microbiomes using a multi-omic approach to better understand the microbial impact on this important ecosystem. In Chapter 1, I first discuss the importance of subsurface shales as an important energy reserve, summarize what is known about microorganisms in these ecosystems, and highlight the strength of using a metagenomic approach to studying shale microbiomes. Subsurface shales are heterogeneous – varying in their mineral content, temperature, and other physiochemical conditions. The microbial communities that persist can have substantial impact on the fractured shale ecosystem and contribute to common challenges in hydrocarbon recovery such as corrosion, souring, and bioclogging. The literature review presented here highlights the need to study the functional potential of shale microbiomes as most studies have mostly focused solely on taxonomic composition of persisting microbial communities, and a vast majority of these studies have focused on samples from wells in the Appalachian Basin. However, functional potential of shale microbiomes across a variety of physiochemical conditions must be considered in order to gain an understanding of the role of microorganisms and what possible influences they may have on hydraulically fractured shales systems. Here, I highlight the need (1) to study the whole community at a functional scale and (2) apply a metagenomic approach to a variety of less characterized shale basins to gain a holistic understanding of shale microbiomes and the effects they may have on the broader ecosystem. In Chapter 2, I apply this metagenomic approach to study the persisting shale microbiomes of three fractured shale wells in the Anadarko Basin – a western shale basin characterized by elevated temperature and salinity. No studies using metagenomics had been applied to shale basins in the western United States prior to this research. We sampled five wells in the Anadarko basin over a timeseries >500 days and preformed NMR metabolomics and metagenomic sequencing to uncover the dominant metabolisms, community composition, and other functional traits of the Anadarko shale microbiome. This system was dominated by a fermentative microbial community and a less-abundant sub-community of inferred sulfate reducing microorganisms. Using paired NMR metabolomics and metagenomics, I demonstrated how many fermentative microorganisms have the potential to degrade common complex polymers, such as guar gum, and have potential to produce organic acids that may serve as electron donors for sulfate and thiosulfate reducing microorganisms. Thus, in this study I provided a framework for how carbon may move through the closed fractured shale ecosystem to sustain the microbial community. Finally, I investigated viral presence and diversity across all thirty-six metagenomes and found that inputs were large sources of viral diversity, but that only an extremely small proportion of viruses recovered from produced fluids were genetically similar to viruses previously reported from fractured shales. I observed that a majority of the dominant and persisting genomes encoded a CRISPR-Cas viral defense system, likely in response to the viral community. This highlights viral defense as another key trait for persisting microorganisms, as viruses are the only predators to bacteria and archaea in fractured shale ecosystems. Overall, this study expanded our knowledge of sulfate and thiosulfate reducing microorganisms in fractured shales, demonstrated the potential for common chemical inputs such as guar gum to be utilized by shale microbiomes, and highlighted how other key traits, such as CRISPR-Cas viral defense systems, may be a crucial trait for persisting shale microbiomes. Building on results from viral analyses in Chapter 2, in Chapter 3 I next sought to investigate the temporal dynamics between hosts and viruses to better understand the role of microbial defense against viruses in fractured shale ecosystems. To do this, I sampled six shale wells in the Denver-Julesburg Basin for >800 days, performed metagenomic sequencing, and identified host (bacterial & archaeal) and viral genomes from this data. I observed evidence of ongoing host defense to viral predation at both the community and genome-level through quantifying spacers from CRISPR arrays in metagenomic reads and MAGs. Through these analyses leveraging timeseries sampling and age differences between the shale wells, I provided evidence that suggested migration toward CRISPR arrays that may be more efficient at protecting the microbial host against a wider suite of viruses. Finally, I observed a temporal increase in host-viral co-existence in the closed, fractured shale ecosystem – suggesting the CRISPR defense does not entirely protect against viral predation. Chapter 4 ultimately leverages the approaches, insights, and data gained from Chapters 2 and 3 to study shale microbiomes at a cross-basin, geographic scale. Here, I collected samples from many collaborators who have previously worked in shale systems, performed metagenomic sequencing, and processed all samples in a standardized pipeline to build a comprehensive genomic shale database. In total, this database contains 978 unique MAGs and >7 million unique genes recovered from 209 metagenomic samples obtained from 36 fractured shale wells spanning eleven shale basins from North America, China, and the United Kingdom. In this chapter I analyze the functional potential of shale microbiomes at a genome-resolved level to better understand the geographic distribution of microbial metabolisms and other key traits that likely contribute to colonization and persistence of microorganisms. Here I also leveraged bioinformatic tools to build a custom annotation summary toolkit to process and analyze the large amount of sequencing data for traits of interest. The complete absence of a taxonomic core microbiome across shale basins illustrated in this chapter underscores the necessity of a genome-resolved and functional approach to studying shale microbiomes. Results from analyzing shale microbiomes at this scale could ultimately help to inform microbial management of fractured shale systems. The final chapter of this dissertation (Chapter 5) summarizes the key findings of my research into fractured shale microbiomes, and the mechanisms that may promote microbial colonization, persistence, and survival in these relatively harsh and economically relevant ecosystems. In this chapter I conclude this work by discussing future directions and lingering knowledge gaps for studying fractured shale microbiomes, as well as implications of these findings for other subsurface engineered ecosystems. Ultimately, this body of work contributes a substantial amount of new and informative insights into the functional potentials of persisting shale microbiomes across broad geographic scales.Item Open Access Multiscale connections between a groundwater dependent ecosystem and socio-hydrology: insight gained from numerical modeling, geospatial informatics, and Bayesian statistics(Colorado State University. Libraries, 2023) Lurtz, Matthew R., author; Morrison, Ryan R., advisor; Bhaskar, Aditi S., committee member; Bailey, Ryan T., committee member; Ross, Matthew, committee memberThe connectivity between floodplain practices and groundwater dependent ecosystems (GDE) is undeniable, yet difficult to measure. Quantifying the connection between ecosystems would be ideal for the conjunctive management of groundwater and surface water resources in an irrigated river valley. In the research presented, a variety of methodologies are used to understand the socio-hydrologic connections between a semi-arid GDE and agro-pastoral practices in southeastern Colorado (USA). I investigated the socio-hydrologic relationships between a GDE and the surrounding floodplain using three approaches. First, I used the output from a calibrated groundwater model and a remote sensing evapotranspiration (ET) algorithm with exploratory statistics. Second, I used remotely sensed vegetation information and socio-hydrologic data in a Bayesian hierarchical time series and spatial statistics models to compliment the first approach by examining new explanatory covariates. Third, a simple regression framework examines the point-scale relationship between groundwater and ET to further dissect results from the first approach at a finer resolution. These three approaches yielded key results. From the first objective, the dual-model comparison agreed with previous ecological research showing a non-linear relationship between ET and groundwater depth (0-5 m), and a threshold was identified at three meters where the rate between ET and groundwater depth change. The time series and spatial statistics objective helped identify a spatial scale threshold to detect temporal trend, lagged intra-seasonal predictors of vegetation water use, and which floodplain characteristics impact vegetation density. This statistical analysis discovered that temporal trend is not detectable at spatial scales larger than catchment size (> 10 km). Monthly temperature and lagged monthly values of precipitation and stream gain-loss (i.e., an return flow indicator variable) are all predictive of temporal changes in riparian vegetation density. Based on the floodplain characteristics tested in the spatial statistics approach, perennial tributaries to the Arkansas River increase vegetation density while the conversion of agriculture to fallow land decrease riparian vegetation density. The third objective highlighted that the process between evapotranspiration and groundwater head is non-linear but depends on temporal scale and plant functional group. The results from these approaches is important for GDE preservation in the face of increasing demand on groundwater supply. The process between groundwater and ET is of particular importance in large scale water balance studies that include a groundwater and surface water interface with need to model the groundwater-ET relationship in natural and agricultural ecosystems simultaneously.Item Open Access Quantifying the impact of climate change and land use change on surface-subsurface nutrient dynamics in a Chesapeake Bay watershed(Colorado State University. Libraries, 2023) Tuladhar, Avalokita, author; Bailey, Ryan T., advisor; Shanmugam, Mohana Sundaram, advisor; Smith, Ryan, committee member; Ross, Matthew, committee memberNutrients such as nitrogen can be harmful to aquatic organisms when loaded to receive water in excessive amounts. Climate change, through possible increases in temperature and variable rainfall, may cause changes in nutrient loading patterns from watersheds. This study assesses the potential impact of climate and land use change on nitrate (NO3) loading in the Nanticoke River Watershed (NRW), Chesapeake Bay region, USA, using an updated version of SWAT+ watershed model that simulates groundwater nitrate fate and transport in a physically based spatially distributed manner. The nutrient loadings from the NRW eventually drain into the Chesapeake Bay, exacerbating eutrophication. The model was simulated for the 2000-2015 time, and tested against measured streamflow, in-stream nitrate loadings, and groundwater head at various stream gages and monitoring wells. Once tested, the model was used to simulate changes in hydrological and nitrate fluxes under two future climates, according to Representative Concentration Pathways (RCP) 4.5 and 8.5, and land use changes as projected by USGS's FORE-SCE model. The projected results show that in the future climate change is to be responsible for an 18-34% and 22-33% decrease in annual average streamflow and a 4-22% and 4-11% decrease in annual average nitrate loading as projected under RCP 4.5 and RCP 8.5 scenarios for future timelines (near 2024-2048, mid 2049-2073 and far future 2074-2099), respectively. The overall decrease in future streamflow is due to higher temperatures resulting in higher evapotranspiration during summer months, offsetting the additional precipitation. The decrease in nitrate loading in the channel is influenced by lower runoff, and elevated nitrate concentration in the soil, leading to increased leaching into groundwater. This surge in soil nitrate concentration results from reduced plant uptake of nitrate due to decreased plant growth/lower crop yields. The stunted plant growth is due to reduced mineralization of nitrogen in the soil which, in turn, is linked to decreasing soil water content and water stress from higher surface temperatures. As compared to the influence of climate, land use change resulted in a minor decrease in future nitrate loading. These results and insights can be used in future nutrient management for similar landscapes. In addition, we show that the updated SWAT+ model can be a useful tool in quantifying and investigating nitrate fate and transport dynamics in coupled surface-soil-aquifer-channel systems, particularly for systems with a strong hydraulic connection between the unconfined aquifer and channel networkItem Open Access Sediment management alternatives analysis in the Louisiana deltaic plain(Colorado State University. Libraries, 2023) Heap, David A., author; Young, Peter, advisor; Zimmerle, Daniel, committee member; Grigg, Neil, committee member; Ross, Matthew, committee memberWhile coastal communities around the world are under threat from rising sea levels, those of Southeast Louisiana are some of the most threatened. Including subsidence, the region could potentially see rates of net sea level rise up to ten times the global mean. There is no shortage of causes for how this situation has come to pass. A Systems Engineering solution needs to be multi-faceted, similar to how the problem was created:- Climate change: like any coastal area, the region has to make hard decisions on how to handle a changing climate, but those choices have significant ramifications for the entire U.S. population, as significant commerce passes through the regional ports in the form of agriculture, oil/gas, petrochemicals, and the fishing industry. - Engineered factors: by controlling the flow of the Mississippi River with the intent of flood protection through the use of levees, floodwalls, and spillways, humans have inhibited the natural processes that could rebuild the wetlands and natural protection barriers. - River navigation: similarly, the locks and dams that allow maritime traffic have trapped the sediment that historically would have flowed down to the delta and built more land buffers against the sea. - Industrial infrastructure: with thousands of miles of navigation channels and pipelines, the wetlands have been cut up into non-natural bodies of water, allowing hurricanes and saltwater intrusion unabated access to delicate ecosystems. - Environmental damage: over 100 years of industrial development, combined with numerous environmental disasters, has compromised the health of the ecosystem. - Invasive species: whether intentionally introduced or not, non-native species, both flora and fauna alike, have wreaked havoc on native populations and weakened deltaic processes. - Stakeholder coordination: with dozens of local, state, and federal government agencies and nonprofit organizations, it is nearly impossible to make everyone happy. - Limited resources: there is a funding gap between the budget needed to implement a successful strategy and what is expected to be available if the status quo is maintained. While there are multiple methods employed to improve coastal resilience, a core strategy as defined by Louisiana's 2023 Coastal Master Plan is the introduction of sediment. The plan suggests two main alternatives of sediment management, that of the Major Diversions and Dredged Sediment. In this work, these two traditional alternatives are considered, and a new proposed approach is introduced, that of Micro Diversions, a concept developed in prior work by the author. All three approaches are described, analyzed, modeled, and compared against each other to determine which would be the most cost effective and appropriate for investment by coastal stakeholders. The compared metric is Cost Benefit over a 50-year time horizon, calculated using the Life Cycle Cost and Net Benefit variables from each alternative. Inherent in the Systems Engineering approach is that the cost variables consider the time value of money. The Major Diversion variables were taken from the stated goals in the Master Plan. The Dredged Sediment variables were forecasted from historical trends on recently completed and/or approved projects. The Micro Diversion variables were formulated from hydrologic software modeling of a limited system and expanded to compare in size to the other alternatives. At a Cost Benefit of $61,773 per acre, the Major Diversion alternative was evaluated to be a better investment than Dredged Sediment or Micro Diversions ($67,300 and $88,206 respectively). Because coastal conditions can change over time, and that the inputs to these alternatives can likewise change, it is suggested to view solutions with a systems-level approach, with the potential to implement complementary alternatives.Item Open Access Soil health indicators for water-limited regions: sensitivity to compost and cropping intensification(Colorado State University. Libraries, 2024) Noble Strohm, Tess, author; Schipanski, Meagan, advisor; Fonte, Steven, advisor; Ross, Matthew, committee memberIn the water-limited agroecosystems of the Great Plains, USA, management strategies such as compost application and cropping system intensification have been promoted to increase soil health and help adapt to climatic variability. However, accurately assessing soil health to support production systems in such regions hinges upon a selection of indicators sensitive to management and linked to essential soil functions, especially those related to soil water dynamics. Using a suite of soil physical and biological parameters, this study assessed the effects of management on soil health metrics and evaluated the extent to which these metrics were related to soil water dynamics utilizing long-term studies in Akron, CO, and Clovis, NM. Soil physical indicators included aggregate stability (mean weight diameter; MWD), bulk density and saturated hydraulic conductivity, while biological indicators included measures of soil macrofauna and microbial communities. Compost application was the primary driver of increased aggregate stability and abundance of soil biota at both sites, though effects of cropping system intensification were observed for some indicators. Measures of soil microbial abundance were correlated with MWD, but saturated hydraulic conductivity was generally not correlated with other measured variables. Our findings indicate that MWD and microbial abundance are linked and sensitive to management, and further research to connect measures of soil biological and physical health to soil water dynamics in semi-arid systems is necessary to develop regionally relevant frameworks for soil health assessments.Item Open Access The development of a decision support system for concurrently evaluating changes in instream and floodplain habitats caused by flow modifications(Colorado State University. Libraries, 2020) Passero, Elaina, author; Morrison, Ryan, advisor; Ross, Matthew, committee member; Julien, Pierre, committee memberAssessments of changes to riverine ecosystems due to flow modifications have historically focused on instream habitat. Thus, considerations of floodplain habitat have often been neglected in assessment tools, creating difficulties for understanding the comprehensive impacts of flow changes to both instream and floodplain environments. To support improved habitat management and protection of naturally variable flows, I developed a decision support system that evaluates both fish and vegetation habitat availability in alternative flow scenarios. This system uses the results of high resolution 2D hydrodynamic models to quantify and map suitable habitat for fish and floodplain vegetation at a range of discharges in a river reach. Depth, velocity, and substrate habitat preference information was used to determine available fish habitat at each modeled discharge. Vegetation habitat was quantified from logistic regression equations relating long-term habitat inundation patterns to probability of occurrence of vegetation. I demonstrate the use of this tool on the Verde River in Arizona, USA. Habitat was evaluated for the historic flow record and two alternative flow scenarios: reduced high flows and reduced baseflows. The two scenarios were compared by evaluating changes in monthly and overall habitat availability, the balance of native and non-native fish habitat, and potential for vegetation movement. Reducing high flows created more habitat for fish with non-natives having the largest increases and led to vegetation encroachment. Reducing baseflows did not affect vegetation habitat, but native and non-native fish habitat was greatly reduced.Item Open Access The effect of projected sea surface temperature change on MJO activity in a warmer climate(Colorado State University. Libraries, 2023) Bowden, Amanda Francine Marie, author; Maloney, Eric D., advisor; Hurrell, Jim, committee member; Ross, Matthew, committee memberThe Madden Julian Oscillation (MJO) consists of a convective region that propagates eastward in the tropics on repeat every 30-90 days with peak amplitude during the Boreal Winter (November - March). Since the MJO modulates extreme weather such as tropical cyclones, atmospheric rivers, and monsoon variability, future MJO changes in a warmer climate have implications for prediction of extreme events. Understanding precipitation pattern changes in a changing climate is critical for fresh-water resources and societal planning for oceanic regions. Decadal variability in the climate system causes patterns of sea surface temperature (SST) change in the tropical Pacific and associated precipitation, humidity, and wind pattern changes to vary from one decade to the next. MJO changes are strongly dependent on the pattern of SST change, and so understanding uncertainty in MJO change in future decades in the context of this decadal variability is the primary motivation for this investigation. Since climate models contain climate variability on decadal timescales, different initial conditions across ensemble members can result in diverse projection outcomes in any given decade. This investigation examines the impact of projected SST and moisture pattern changes over the 21st Century on MJO precipitation and zonal wind (850 mb) amplitude changes using 80 members with the SSP370 radiative forcing scenario from the Community Earth System Model 2 (CESM2) Large Ensemble. The projected SST and moisture pattern changes can be weighted more toward the central or eastern equatorial Pacific in earlier parts of the 21st Century across ensemble members, although becomes strongly El Niño-like later in the century. Ensemble members with stronger MJO precipitation amplitude in a given period are characterized by stronger El Niño-like east Pacific warming, associated with a strengthened meridional moisture gradient. As interpreted through moisture mode theory, greater east Pacific warming supports a stronger MJO by enhancing propagation through a stronger meridional moisture gradient, and enhancing MJO amplitude through a stronger vertical moisture gradient. The investigation supports the hypothesis that projected SST and moisture pattern changes influence MJO activity, and also highlights the importance of understanding decadal climate variability for interpreting changes in water resources of oceanic regions.Item Open Access Understanding the daily to decadal evolution of mountain glaciers in Alaska and high mountain Asia from satellite remote sensing(Colorado State University. Libraries, 2024) Zeller, Lucas R., author; McGrath, Daniel, advisor; Gallen, Sean, committee member; Ross, Matthew, committee member; Florentine, Caitlyn, committee memberGlaciers are important components of mountain ecosystems, mountain hydrological systems, and the global water cycle. Improving our scientific understanding of the spatial and temporal variability in glacier changes and the physical processes that drive those changes will allow better prediction of future glacier evolution. In this dissertation, I explore ways in which satellite-based remote sensing products can be used to study mountain glaciers across a wide range of spatial and temporal scales, with a specific focus on Alaska and High Mountain Asia. The accumulation area ratio (AAR) of a glacier reflects its current state of equilibrium, or disequilibrium, with climate and its vulnerability to future climate change. In Chapter 1, I present an inventory of glacier-specific annual accumulation areas and equilibrium line altitudes (ELAs) for over 3,000 glaciers in Alaska and northwest Canada (88% of the regional glacier area) over the 2018–2022 period derived from Sentinel-2 satellite imagery. I find that the five-year average AAR of the entire study area is 0.41, with an inter-annual range of 0.25–0.49. More than 1,000 glaciers, representing 8% of the investigated glacier area, were found to have effectively no accumulation area. Summer temperature and winter precipitation from ERA5-Land were found to be effective predictors of inter-annual ELA variability across the entire study area (R2=0.47). An analysis of future climate projections (SSP2-4.5) shows that ELAs will rise by 170 m on average by the end of the 21st century. Such changes would result in a loss of 25% of the modern accumulation area, leaving more than 1,900 glaciers (22% of the investigated area) with no accumulation area. These results highlight the current state of Alaska glacier disequilibrium with modern climate, as well as their vulnerability to projected future warming. In High Mountain Asia, many glaciers have thick debris cover over the majority of their ablation zones, earning them the name 'debris-covered glaciers'. Supraglacial lakes (SGLs) play an important role in debris-covered glacier (DCG) systems by enabling efficient interactions between the supraglacial, englacial, and subglacial environments. Developing a better understanding of the short-term and long-term development of these features is needed to constrain DCG evolution and the hazards posed to downstream communities, ecosystems, and infrastructure from rapid drainage. In Chapter 2, I present an analysis of supraglacial lakes on eight DCGs in the Khumbu region of Nepal by automating SGL identification in PlanetScope, Sentinel-2, and Landsat 5–9 satellite images. I identify a regular annual cycle in SGL area, with lakes covering approximately twice as much area during their maximum annual extent (in the pre-monsoon season) than their minimum annual extent (in the post-monsoon season). The high spatiotemporal resolution of PlanetScope imagery (∼ daily, 3 m) shows that this cycle is driven by the appearance and expansion of small lakes in the upper debris-covered regions of these glaciers throughout the winter. Decadal-scale expansion of large, near-terminus lakes was identified on four of the glaciers (Khumbu, Lhotse, Nuptse, and Ambulapcha), while the remaining four showed no significant increases over the study period. The seasonal variation in SGL area is of comparable or greater magnitude as decadal-scale changes, highlighting the importance of accounting for this seasonality when interpreting long-term records of SGL changes from sparse observations. The complex spatiotemporal patterns revealed in this analysis are not captured in existing regional-scale glacial lake databases, suggesting that more targeted efforts are needed to capture the true variability of SGLs on large scales. In Chapter 3, I expand these methods across a wider spatial extent by using the Landsat 5, 7, 8, and 9 archive to delineate SGLs on debris-covered glaciers across all of High Mountain Asia at near-annual cadence from 1988–2023. I find that SGL area has increased throughout the study period, rising to 17.2 km2 (0.7% of the investigated debris-covered area) in 2023, compared to ~8 km2 (0.3% of debris-covered area) in 1988. SGL growth is most concentrated in the Himalaya and Nyainqêntanglha regions, which have also experienced the greatest rates of 20th and 21st century mass loss. The 21st century SGL growth is concentrated almost entirely near the termini of these glaciers, indicating the possibility of continued growth and coalescence into large proglacial lakes. Areas of high SGL concentration are predominantly found in areas with lower surface gradients, low velocity, and thicker debris cover. Glaciers with high SGL concentrations are found to have steeper longitudinal gradients of thinning, with greater thinning rates further from the terminus resulting in lower surface slopes and more concave geometries throughout their entire debris-covered extents. However, the representative longitudinal thinning pattern of glaciers without substantial SGL formation have become more similar to this pattern in recent years, suggesting that more of these glaciers may be primed for SGL formation in the future.