Browsing by Author "Bailey, Ryan, committee member"
Now showing 1 - 17 of 17
Results Per Page
Sort Options
Item Open Access Confronting the natural variability and modeling uncertainty of nonpoint source pollution in water quality management(Colorado State University. Libraries, 2017) Tasdighi, Ali, author; Arabi, Mazdak, advisor; Bledsoe, Brian, committee member; Bailey, Ryan, committee member; Hoag, Dana, committee memberNonpoint source pollution is the primary cause of impaired water bodies in the United States and around the world. Hence, managing the water quality is hinged mainly on controlling this type of pollution. However, characterization of nonpoint source pollution is extremely difficult due to high inherent natural variability and uncertainty. Nonpoint source pollution loads depend on climate, land use, and other environmental conditions that are highly variable by nature. On the other hand, since it is often infeasible to measure pollutant loads from nonpoint sources within a watershed using monitoring campaigns, models are increasingly used to estimate these loads. Models are simplified representations of reality. Consequently, they are subject to various sources of uncertainty including: model parameters, input data (climate, land use, etc.), model structure (conceptualization), and measurement data (streamflow, nutrient concentrations or loads, etc.).Item Open Access Evaluating covariance-based geostatistical methods with bed-scale outcrop statistics conditioning for reproduction of intra-point bar facies architecture, Cretaceous Horseshoe Canyon Formation, Alberta, Canada(Colorado State University. Libraries, 2022) McCarthy, Andrew Louis, author; Stright, Lisa, advisor; Ronayne, Michael, committee member; Bailey, Ryan, committee memberGeostatistical characterization of petroleum reservoirs typically suffers from problems of sparse data, and modelers often draw key parameters from analogous outcrop, numerical, and experimental studies to improve predictions. While quantitative information (bed-scale statistical distributions) from outcrop studies is available, translating the data from outcrop to models and generating geologically-realistic realizations with available geostatistical algorithms is often problematic. The overarching goal of this thesis is to test the capacity of covariance-based geostatistical methods to reproduce intra-point bar facies architecture while guiding those algorithms with bed-scale outcrop statistics from the Late Cretaceous Horseshoe Canyon Formation in southeastern Alberta. First, general facies architecture reproduction is tested with 2- and 3-facies synthetic and outcrop-based experiments with variable hard data, soft data weight, and soft data reliability. Next, 3-D sector models compare performance of different geostatistical simulation methods: sequential / co-sequential indicator, plurigaussian, and nested truncated gaussian. Findings show that despite integration of outcrop statistics, all conventional covariance-based geostatistical algorithms struggle to reproduce complex facies architecture that is observed in outcrop. Specifically, problems arise with: 1) low-proportion facies and 2) a weak statistical relationship between hard data (measured sections) and soft data (probability models). Nested modeling partially mitigates low-proportion issues and performs better as a result.Item Open Access Evaluating spatial and temporal controls on recharge fluxes in a stream-alluvial-bedrock aquifer system(Colorado State University. Libraries, 2023) Cognac, Kristen, author; Ronayne, Michael, advisor; Bailey, Ryan, committee member; Rathburn, Sara, committee member; Stright, Lisa, committee memberThe dynamics and timescales associated with natural and induced recharge to aquifers dictate whether and for how long groundwater resources are sustainable. This dissertation contains three studies which apply groundwater flow and geostatistical modeling to evaluate spatial and temporal controls on recharge fluxes in a stream-alluvial-bedrock system. Each study is based on a recharge mechanism that occurs within the Denver Basin aquifer system, a regionally significant water supply for which long-term pumping and active aquifer depletion call for improved characterizations of recharge. While recharge is the theme of this dissertation, I don't attempt to directly estimate recharge for the Denver Basin, but rather to investigate and expose dynamics of recharge that are essential for accurate conceptualizations and estimates of recharge. The first study investigates controls and timescales associated with streambed fluxes which are an important component of seepage recharge along mountain-front streams. Streambed fluxes are highly variable through time and space, having a range of implications for stream-aquifer processes. While spatial variations in streambed flux have been heavily characterized, temporal variability has been limited to short-term or low-frequency measurements. This study calculates high-frequency time series of Darcy-based streambed fluxes over a three-year period using water level and temperature inputs from shallow (<1.5m) nested streambed piezometers installed in two mountain-front streams in Colorado, USA. Results reveal important conclusions about controls and patterns of temporal variability. Three predominant temporal scales of variability, sub-daily (<1day), daily (>1d; <1y), and interannual (>1y), are quantified through statistical measures. Sub-daily variability was related to ET, temperature-induced changes in hydraulic conductivity, and variable stream stage while daily variability was highly seasonal and related to specific events on the channel (e.g., beaver dams). The magnitude of sub-daily variability was significant compared to daily variability (ratio 0.03 to 0.7). Annual median fluxes at each site varied across years, but typically remained consistent in order of magnitude and direction. A strong linear correlation characterizes the relationship between the daily variability and the median annual flux at individual sites, highlighting how sites with greater fluxes also exhibit greater temporal variability. The temporal flux variations documented in this study have important implications for calculations and interpretations of hyporheic exchange and groundwater recharge. Results provide a basis for quantifying temporal variations in streambed fluxes and highlight the extent to which fluxes vary over multiple timescales. Chapters 3 and 4 are organized to progress vertically downward within the system to investigate controls for inter-aquifer exchange between the alluvial and bedrock aquifer, an important component of recharge to the underlying bedrock aquifer system. In Chapter 3, the potential for and controls of hydraulic disconnection between the alluvial and bedrock aquifer are investigated. Hydraulic disconnection occurs when unsaturated conditions develop between a stream and water table causing seepage rates to stabilize with additional water table drawdown. In this study, I demonstrate that hydraulic disconnection can occur between an alluvial and bedrock aquifer when unsaturated conditions develop between the two water tables and inter-aquifer flow rates stabilize with subsequent drawdown. Variably saturated flow modeling is performed to simulate the effects of drawdown on alluvium to bedrock flow rates (A-B flow). Bedrock aquifer heterogeneity is represented through object-based geostatistical models that are conditioned to wellbore data from the Denver Basin aquifer system. The Monte Carlo framework includes 200 heterogeneity realizations across a range of sandstone fractions. Results document the formation of unsaturated regions beneath the alluvium in all models, particularly where sandstone channels underlie thinner low-permeability mudstones. Three-dimensional heterogeneity creates complex saturation patterns that result in localized flow paths, spatially varying disconnection, and a gradual transition to hydraulic disconnection as the regional water table is lowered. Successive changes in A-B flow decrease over the course of simulations by 80% to 99% and final rates approach stability as indicated by changes of <1% between successive stress periods. Of the 200 models, 190 reach full hydraulic disconnection and 10 conclude with a transitional flow regime. Dynamic connectivity metrics developed within the study strongly explain flow results. I also evaluate the aspects of heterogeneity that are most likely to produce disconnection, highlighting several factors that influence disconnection potential. Chapter 4 evaluates the potential for a beaver dam to drive flow across the alluvial-bedrock contact. Beavers construct dams which promote a range of surface and near-surface hydrologic processes, however, the potential for beavers to influence deeper aquifer dynamics is less often, if ever, considered. In this study I consider the potential for a beaver dam, specifically increased stream stage and width upstream of a dam, to drive deeper flow from an alluvial to bedrock aquifer. I utilize a numerical groundwater flow model to simulate the effects of the beaver dam on inter-aquifer exchange rates. The base case model is parameterized based on observations from a beaver dam constructed on Cherry Creek in 2020 and the stream-alluvial-bedrock aquifer sequence in the Denver Basin in previous chapters. I also test whether the influence of the beaver dam is sensitive to the alluvial-bedrock contact depth, beaver pond depth, and hydraulic properties by simulating flow across a range of sensitivity scenarios. Model results document an increase in alluvial to bedrock flow on the order of 0.5% to 4%, depending on the contact depth, beaver pond depth, and hydraulic properties. Changes in hydraulic head due to the dam propagate deep into the aquifer (>30m), highlighting the potential for deeper aquifer impacts. The effect of the beaver dam is greatest for shallow alluvial-bedrock contact depths, deeper pond depths, and lower hydraulic conductivity contrasts between the alluvial and bedrock aquifer. Overall, results document the potential for beavers to influence deeper aquifer fluxes where regional hydraulic gradients are downward, highlighting broader potential for beaver dams to enhance aquifer recharge in deeper aquifer settings.Item Open Access Evaluating the impact of hierarchical deep-water slope channel architecture on fluid flow behavior, Cretaceous Tres Pasos Formation, Chile(Colorado State University. Libraries, 2021) Ruetten, Andrew, author; Stright, Lisa, advisor; Ronayne, Michael, committee member; Bailey, Ryan, committee memberChannelized deep-water reservoirs inherently contain sub-seismic scale heterogeneity, resulting in uncertainty when evaluating reservoir connectivity and flow patterns. Stratigraphic architectural features, including stacked channel elements, channel element fill, mass transport deposits (MTDs), and channel base drapes, can have a complex and significant impact on fluid flow pathways. While this detailed stratigraphic architecture can be difficult to capture at the development scale, it can be effectively modeled at the sector scale using high-resolution outcrop data. The characterization of flow behaviors and reservoir performance at this finer scale can then be used in the construction of lower-resolution development-scale simulations. This study uses a three-part sensitivity analysis to test how fluid flow behavior responds to channel element stacking patterns, net to gross ratio, channel base drape coverage, and MTD properties. First, simplified models are used to isolate key flow behaviors. Then, field data is incorporated from the seismic-scale Laguna Figueroa outcrop of the Cretaceous Tres Pasos Formation, Magallanes Basin, Chile to construct a deterministic outcrop model that incorporates realistic stacking patterns and architectural features, including MTDs. Finally, stochastic object-based methods are used to try to replicate the flow characteristics of the outcrop model using established geostatistical methods and limited data input. Fluid flow was simulated using a constant flux aquifer at the base of the model and three producing wells at the top, and the results of the three modeling methods were compared in an effort to elucidate key flow behaviors.Item Open Access Growth, recovery and bioaccumulation of alfalfa (Medicago sativa) and spinach (Spinacia oleracea) exposed to cyanotoxins in agricultural environments(Colorado State University. Libraries, 2020) Nezat, Caryn Janel, author; Omur-Ozbek, Pinar, advisor; Peebles, Christie, committee member; Bailey, Ryan, committee memberHarmful algal blooms (HABs) are a growing concern for surface water resources around the globe. With increasing pressure on our limited fresh water resources due to climate change, the risk of contamination from HABs and the cyanobacterial toxins that accompany blooms, exacerbates the problem. Adverse health effects from cyanotoxin exposure has been documented in human and animal mortality and morbidity cases worldwide. Nationally, the presence and severity of HABs has prompted multiple cyanotoxins, including cylindrospermopsin (CYN) and microcystins (MCLR), to be listed on the USEPA Drinking Water Contaminant Candidate List-4 (CCL4) requiring many public systems to monitor for cyanotoxin presence. Recognizing this risk, the World Health Organization (WHO) has long established guidelines to acceptable levels in surface waters based on exposure pathways and use. Further concerns have arisen as our understanding about cyanotoxins has been expanded by research. The purpose of this experiment was to determine 1) effects of toxin exposure during germination, 2) the effects of CYN and MCLR on agricultural crops exposed to toxins during vegetative and mature growth stages, 3) crops ability to recover from toxin exposure and 4) to quantify amount of cyanotoxin accumulated within crop tissue after exposure to cyanotoxins. Germination results indicated exposure to CYN and MCLR did not decrease the rate of germination of alfalfa or spinach. Further, alfalfa and spinach had increased primary root growth for seeds exposed to cyanotoxins. During early vegetative exposure, spinach showed increased biomass and larger leaf area when exposed to MCLR and CYN. After a recovery period spinach plants exposed to CYN showed increased biomass compared to controls. Alfalfa plants exposed to MCLR in vegetative stages had significantly more biomass when compared to controls and this trend was observed after the recovery period. Results of alfalfa exposed during mature growth stages to CYN and MCLR indicated it was more sensitive to CYN, however both toxin treatments resulted in increased biomass production. After one- and two-weeks of recovery the MCLR treated alfalfa biomass remained higher than controls. Bioaccumulation of CYN and MCLR was observed in alfalfa exposed early to the toxins and detectable levels were observed after the one-week recovery period. Spinach accumulated MCLR during early exposures and had detectable levels in the stems after one-month recovery. During mature exposure, alfalfa initially only had detectable levels of MCLR, which decreased over the recovery periods. However, the presence of CYN was not detected until one-week prior to the final toxin exposure. These findings support the growing concern that use of cyanotoxin contaminated irrigation water can be an additional exposure route for ingestion of toxins and increased risk of adverse health effects. Further studies into the subsurface fate of cyanotoxins will further increase the understanding of their bioavailability and persistence in soil.Item Open Access Hydrologic impacts of lined gravel pits, Colorado Front Range(Colorado State University. Libraries, 2018) Rach, Gavin, author; Ronayne, Michael, advisor; Sanford, William, committee member; Bailey, Ryan, committee memberSand and gravel quarries are a major source of natural aggregate. Gravel pits often excavate below the water table and therefore can influence alluvial aquifer groundwater flow directions and groundwater-surface water interaction. By regulation in the state of Colorado, low-permeability liners are installed after extraction to minimize water seepage into the pit. The liner impedes flow and disturbs the local water table, creating mounding on the upgradient side and shadow drawdown on the downgradient side. To better understand the magnitude and extent of these effects, numerical groundwater modeling was conducted for a study area along the Saint Vrain Creek alluvial aquifer in Colorado that contains an active gravel pit. The numerical model was based on a revised conceptual model, including a reinterpretation of the bedrock surface, and was calibrated using measured groundwater levels and estimated groundwater-surface water exchange rates constrained by streamflow gaging data. Two transient modeling scenarios were developed: a base case pre-mining scenario and a post-mining lined-pit scenario. The hydrologic effects of the pit liner were quantified through a detailed comparison of the scenarios. Model results indicate that the liner has a significant effect on water-table elevation in the vicinity of the pit during the non-irrigation season (October-March). In March, upgradient mounding produced by the liner exceeds 0.5 m at an approximate distance of 100 m, whereas the drawdown exceeds 0.3 m at this distance on the downgradient side of the pit. The magnitude of these liner-induced changes is less than other seasonal variability in hydraulic head, particularly the variability associated with irrigated agriculture (seasonally active irrigation ditches). During the irrigation season, simulated hydraulic heads are similar in both model scenarios, demonstrating that irrigation ditches are a major control on groundwater flow. Despite significant water table elevation change in parts of the year, groundwater discharge to the stream increased by 0.11% of the total streamflow at its maximum, demonstrating this particular pit liner has a negligible effect on the Saint Vrain Creek.Item Open Access Investigation of dual-pulse laser plasmas for ignition of fuel-air mixtures(Colorado State University. Libraries, 2020) Butte, Carter Vincent, author; Yalin, Azer, advisor; Marchese, Anthony, committee member; Bailey, Ryan, committee memberProgress towards more complex combustion applications has demanded more advanced and versatile ignition techniques. One attempt to address some of the concerns associated with well-established techniques such as spark plugs and igniters is laser plasma ignition. Advantages of laser ignition include flexibility of spark location and timing, reduced NOx formation, leaner engine operation, increased combustion efficiency, and greater system longevity at elevated pressures. Additionally, the non-intrusive nature of laser plasmas results in more unperturbed kernel evolution, as mounting hardware is not required. This is an advantage when compared with spark plug or igniter electrodes which typically act as heat sinks quenching the flame. However, large input energies, complications with beam delivery, and undesirable kernel dynamics have impeded field implementation. Our approach to address these challenges uses a dual-pulse laser plasma where an ultraviolet (UV) beam preionizes a gas mixture and a second near infrared (NIR) beam increases the energy and ionization state of the gas. The use of this technique decouples the processes responsible for ionization, predominantly multiphoton ionization (MPI) and electron avalanche ionization (EAI) through inverse bremsstrahlung absorption, and allows for tailoring of plasma properties through adjustments to beam energies and delay time. Recent work has shown that dual-pulse laser plasmas not only reduce energy requirements but also enhance ignition characteristics such as combustion efficiency, particularly around the lean limit.6 The present thesis serves to fill voids in the existing literature with regards to plasma properties and ignition characteristics in various fuels, as well as present a new resonant preionization scheme targeting molecular oxygen at Ī»=287.5 nm. Four laser plasmas are investigated in this work: non-resonant single pulse (Ī»=1064 nm), non-resonant dual-pulse (preionization at Ī»UV=266 nm with energy-addition at Ī»NIR=1064 nm), resonant single-pulse (Ī»REMPI=287.5 nm), and resonant dual-pulse plasma (preionization at Ī»REMPI=287.5 nm and energy addition at Ī»NIR=1064 nm). Each of these plasmas are analyzed for electron density and gas temperature using combined Rayleigh Thomson scattering, and are studied for ignition of propane-air, methane-air, and hydrogen-air mixtures. In the analysis, these experimental results are combined with past results to give a comprehensive picture of the ignition abilities of single pulse and dual-pulse plasmas in propane-air, methane-air, and hydrogen-air mixtures. Together, knowledge of plasma properties and ignition characteristics give us a more complete picture of the capabilities and limitations of each plasma for combustion applications.Item Open Access Modeling effects of microvilli on somatic signal propagation(Colorado State University. Libraries, 2018) Aldohbeyb, Ahmed A., author; Lear, Kevin, advisor; Vigh, Jozsef, committee member; Bailey, Ryan, committee memberThe electrical behavior of small compartments in neurons such as dendritic spines, synaptic terminals, and microvilli has been of interest for decades. Most of these fine structures are found in the dendrite, where most excitatory inputs are received, or in the axon where the action potential is generated and propagates. However, a recent study has shown expression of sodium voltage-gated channels (VGCs) in the soma of intrinsically photosensitive retinal ganglion cells (ipRGCs). Confocal imaging locates these sodium VGCs outside the main soma membrane, which implies that the VGCs occur in structures that protrude from the soma but are too small to be resolved with conventional optical microscopy. An investigator has hypothesized the voltage-gated sodium channels are positioned in microvilli. The microvilli hypothesis raises the question of the role of voltage-gated sodium channels on microvilli and more specifically what effect they would have on propagation of signals in the soma. The nanoscale dimensions of the microvilli, which are much smaller than patch-clamp probes, prevent conventional electrical studies that isolate individual compartments. In the absence of direct, high-spatial resolution measurements, computational models are valuable tools for developing a better understanding of the electrical behavior of the neuronal compartments. Well known models such as HodgkināHuxley models and cable theory have been the foundation of many advances in neuroscience. In this work, initial insights about the role of somatic microvilli are being generated using an equivalent circuit model based on the cable equation. For the circuit model, microvilli stubs containing resistor-capacitor networks and sodium channels are treated as branches off the main soma membrane. Circuit models of the soma membrane without microvilli serve as controls. The circuit models were simulated using Simulink. The results show that voltage-gated sodium channels placed on the main soma membrane or on the microvilli increase the amplitude of somatic signals as they propagate to the axon initial segment. Moreover, restriction of the VGCs to the somatic microvilli reduces the probability of misfires originating from spontaneous ion channel opening while still enhancing above threshold depolarizations propagating in the main soma membrane. For comparison, simulations of somatic signal propagation were also performed using the NEURON software as it readily incorporated the Hodgkin and Huxley model, including both sodium and potassium voltage-gated channels. The dendritic input signal was generated using the current clamp technique. The results show that the presence of VGCs on the main soma membrane lower the threshold for triggering the AIS to generate action potential. However, restricting sodium VGCs to the microvilli only did not initiate an action potential at the AIS. The ability of the microvilli Na+ VGCs to serve as excitatory inputs directly to the soma in the absence of the dendritic input was also investigated using NEURON. Using a current clamp, current was injected at the tip of the microvilli and the signal was recorded at the AIS. The results show that the signal at the AIS increases linearly with the injected current. However, the amplitude of the AIS potential was lower than the microvilli signal due to the high microvilli neck resistance. The results support the view that the microvilli act as electrical compartments that attenuate the microvilli VGCs' signals.Item Open Access Optimizing operation and design of aquifer storage and recovery (ASR) wellfields(Colorado State University. Libraries, 2019) Alqahtani, Abdulaziz, author; Sale, Tom, advisor; Grigg, Neil, committee member; Bailey, Ryan, committee member; Ronayne, Michael, committee memberSustained production of groundwater from wells in wellfields can lead to declining water levels at production wells and concerns regarding the sustainability of groundwater resources. Furthermore, minimizing energy consumption associated with pumping groundwater is a growing concern. Aquifer Storage and Recovery (ASR) is a promising approach for maintaining water levels in wells, increasing the sustainability of groundwater resources, and minimize energy consumption during groundwater pumping. Therefore, studying the importance of ASR in sustaining water levels and minimizing energy consumption is critical. In the first part of this dissertation, an analytical model relying on superposition of the Theis equation is used to resolve water levels in 40 wells in three vertically stacked ASR wellfields. Fifteen years of dynamic recovery/recharge data are used to obtain aquifer and well properties. Estimated aquifer and well properties are used to predict water levels at production well. Close agreement between modeled and observed water levels support the validity of the analytical model for estimating water levels at ASR wells. During the study period, 45 million mĀ³ of groundwater is produced and 11 million m3 is recharged leading to a net withdrawal of 34 million mĀ³ of groundwater. Rates of changes in recoverable water levels in wells in the Denver, Arapahoe and Laramie-Fox Hill Aquifers are 0.20, -0.91, and -3.48 m per year, respectively. To quantify the benefits of recharge, the analytical model is applied to predicting water levels at wells absent the historical recharge. Results indicate that during recovery and no-flow periods, recharge has increased water levels at wells up to 60 m compared to the no-recharge scenario. On average, the recharge increased water levels at wells during the study period by 3, 4, and 11 m in the Denver, Arapahoe, and Laramie Fox-Hills Aquifers, respectively. Overall, the analytical model is a promising tool for advancing ASR wellfields and ASR can be a viable approach to sustaining water levels in wells in wellfields. In the second part of this dissertation, a simulation-optimization model (ASRSOM) is developed to optimize ASR wellfield operations. ASRSOM combines an analytical hydraulic model and a numerical optimization model to optimize wellfield operations. The objective function used to minimize energy consumption Ļ (Lā“) is the temporal integral of the products of temporally varying total dynamic head values and pumping rates. Comparison of ASRSOM results to work by others for idealized aquifer operations supports the validity of ASRSOM. Four scenarios were simulated to evaluate the role that optimization of operations and aquifer recharge play in reducing the energy required to lift groundwater out of aquifer. A 10-year study period is considered using data from a municipal ASR wellfield. Optimization decreased Ļ by 19.6%, which yields an estimated reduction of 2,179 MW hours of power and 1,541 metric tons of atmospheric carbon. For the condition considered, recharge reduced power by 1%. The limited benefit of recharge is attributed to the small recharge volume in the case study and the short duration of the analysis. Additional opportunities to address economic and environmental impacts associated with lifting groundwater out aquifer include optimizing the position of wells and factors controlling total pumping head. In the third part of this dissertation, the sensitivity of well-spacing in ASR wellfields to critical parameters is studied. The parameters studied are aquifer transmissivity and storativity, wells flowrate and the frequency of recharge and recovery. It has been found that larger well-spacing are appropriate for lower transmissivity and storativity, and larger wells flowrate and frequency. More work is needed to fully understand the optimal well-spacing of wells in ASR wellfields associated with more realistic storage and recovery schedules, and more complex wellfields. Overall, work supported the possibility that wells in ASR wellfields can be spread more closely than wells in conventional production wellfields.Item Open Access Parameter estimation methods for models of major flood events in ungauged mountain basins of Colorado(Colorado State University. Libraries, 2021) Irvin, Ben Christopher, IV, author; Niemann, Jeffrey D., advisor; Schumacher, Russ S., committee member; Bailey, Ryan, committee memberAccurate hydrologic modeling of ungauged mountain basins plays an important role in ensuring the safety of Colorado's dams. Recent research has shown that infiltration-excess runoff, saturation-excess runoff, and subsurface stormflow can all contribute to streamflow from major storms in Colorado's mountains, and the soil moisture accounting (SMA) method in HEC-HMS has been suggested as an appropriate approach to model these mechanisms. However, SMA requires estimation of parameters that have not been previously considered in dam safety analyses. The objectives of this work are to (1) evaluate simplifications to the modeling process that would reduce the number of required parameters and (2) develop methods to estimate the remaining parameters in ungauged mountain basins of Colorado where calibration to observed discharges is not possible. The proposed simplifications and parameter estimation methods are tested for five basins in the Front Range and three basins in the San Juan Range that have streamflow data available for major flood events. For these historical events, the proposed uncalibrated models produce the same streamflow generation processes as calibrated models and the predicted peak discharges from the uncalibrated models usually have 25% errors or smaller. For design storms, the peak discharges from the proposed uncalibrated models can differ substantially from the peak discharges from calibrated models but are conservative relative to the envelope of observed peak discharges.Item Open Access Reactive transport modeling of nutrients in arctic tundra streams(Colorado State University. Libraries, 2014) Kang, Woochul, author; Gooseff, Micheal N., advisor; Ramirez, Jorge A., committee member; Bailey, Ryan, committee member; Covino, Tim, committee memberThe one dimensional solute transport inflow and storage (OTIS) model is used to simulate the transport of non-conservative and conservative solutes in arctic tundra streams. Field research was conducted in I8 Inlet and Outlet streams, (in northen Alaska) which are located upstream and downstream of 18 Lake between June and September 2010 and 2011 (thaw season) and these two streams are classified as alluvial, low gradient, headwater tundra streams. Repeat solute injections were conducted on both streams. Two sets of solute injections were made, Injection A is sodium chloride (NaCl) and phosphate (PO4) and Injection B is sodium chloride (NaCl) and ammonium (NH4). The sodium chloride is conservative and other two solutes are non-conservative solutes. With the observed concentration data, OTIS-P was used to estimate the model parameters values related to transport (dispersion and advection), transient storage and nutrient uptake mechanisms, by nonlinear least squares fit. The dispersion coefficient and main channel cross-sectional area parameters represented transport, storage zone cross-sectional area and exchange coefficient parameters represent transient storage, and 1st order decay coefficient in main channel and storage zone represent nutrient uptake. Additionally, transport and uptake metrics were calculated with estimated parameters. We assumed discharge, stream water temperature, and date (as a surrogate for thaw depth beneath the stream) were potential control variables on transport, transient storage, and nutrient uptake processes. Linear regression was conducted to identify potential relationships between these estimated parameters and metrics and control variables. Hydraulic controls are positively correlated with transport and transient storage mechanisms and stream temperature has positive relationships with nutrient uptake of non-conservative solutes (NH4 and PO4). Although, this study did not found direct influence of date (indicate of thaw depth) as a control, active layer condition is an important factor in solute transport dynamics in arctic region. Moreover, additional controls should be considered to explain solute transport dynamics more exactly. Beyond the scope of this study, for example, stream ecosystem status or activity may more directly explain NH4 and PO4 uptake variability.Item Open Access Spatial arrangement of stormwater infiltration affects partitioning of subsurface storage and baseflow timing(Colorado State University. Libraries, 2019) Choat, Benjamin, author; Bhaskar, Aditi, advisor; Bailey, Ryan, committee member; Ronayne, Michael, committee memberUrban stormwater management is using distributed facilities that treat stormwater near where it falls at an increasing rate. These facilities are often designed to infiltrate water that would have previously been conveyed overland. By directing water that would have previously made it to receiving streams very quickly via overland flow into subsurface flow paths, the soil moisture, groundwater, and stream flow regimes are altered. While these alterations may have significant implications for urban watershed management, there remains a lack of knowledge about how spatial arrangements of infiltration focused facilities may affect catchment scale water-balances, including subsurface storage and streamflow. In particular, little focus has been given to relating site-scale behavior with catchment scale response. This project used a physically-based numerical model, ParFlow, to investigate the relationships between spatial arrangements of infiltration facilities, subsurface partitioning of water between unsaturated and saturated zones, and baseflow response duration and timing. Our findings show that more spatially distributed infiltration facilities, as compared to spatially-clustered infiltration facilities, encourage greater unsaturated zone storage, less saturated zone storage, and more total subsurface storage in scenarios where surface ponding is not severe. Depth to water table beneath infiltration facilities was found to be the main driver of observed differences in partitioning of subsurface storage. In our lowest conductivity soil, silt, severe groundwater mounding was observed at steady-state with significant surface ponding. In a catchment with high permeability and diffusivity, baseflow response to precipitation was delayed in the clustered infiltration scenario compared to the distributed scenario. The clustered scenario resulted in more baseflow after longer inter-event durations but lower baseflow between sequential precipitation events with short inter-event durations. In the same catchment, antecedent moisture was shown to amplify sensitivity of baseflow response to clustered infiltration spatial arrangement. These results can be used to help guide decisions about spatial locations of stormwater infiltration facilities to meet urban watershed management goals such as increasing plant available water, increasing aquifer recharge, producing more consistent or dynamic baseflow, and quicker or more delayed baseflow responses to precipitation.Item Open Access Subsurface water storage assessment model(Colorado State University. Libraries, 2015) Alqahtani, Abdulaziz A., author; Sale, Tom, advisor; Bailey, Ryan, committee member; Ronayne, Michael, committee memberWater storage is an essential part of water resources management schemes. Due to the high cost and escalating risks of building new surface reservoirs, water managers are becoming interested in employing more effective alternatives. Subsurface water storage is getting attention as one of these alternatives. However, due to lack of experience and tools to estimate the cost and effectiveness of subsurface water storage, water managers are reluctant to adopt this alternative. Available tools/models are only case specific; hence in this study, we develop a general model for subsurface storage and recovery. The model estimates the cost of the subsurface water storage and recovery using wells in bedrock. The model takes monthly river flow, population, and per capita demand as inputs to determine capital cost and operation and maintenance costs for the lifespan of the proposed project. To account for uncertainty in the input parameters, the model has the capability to perform stochastic analyses as well. Furthermore, the model includes the option of modular expansion of infrastructure through time, potentially reducing total and operation and maintenance costs. An application of the model is advanced based on the conditions in the vicinity of Fort Collins, Colorado. Critically, work presented herein should not be taken as a rigorous analysis of the issues faced by the city of Fort Collins. The application is simply a demonstration of what can be done with the tools developed in this thesis. The general premise of the application is creating new water storage in the Fountain Formation, north of Fort Collins. This model uses either deterministic or stochastic inputs. Since the deterministic model's inputs and outputs are both fixed numbers, the model is relatively simple. However, this type of input will yield specific results and does not consider the possibility of inputs varying through time. It misses a key challenge of water projects, the temporal variability in available water and demand. In Stochastic Analysis, inputs are varies from year to year and from month to month, allowing the system to accommodate wet or drought years, making the model more reliable for calculating the cost of system. One hundred simulations were performed using the stochastic model to estimate the range of variability of outputs. Except total pumping and additional storage, other outputs have small coefficients of variation, which show that they are less sensitive to uncertainity in input variables. The coefficient of variation for cost variables are around 0.1 (i.e., costs are expected to vary within Ā±10% of the estimated mean cost). As different cost components estimated by deterministic model are within Ā±10% of estimated mean cost from stochastic model. Therefore, we conclude that the deterministic model estimates different cost components fairly well. Both models, deterministic and stochastic, have been applied to a scenario predicted on conditions faced by the city of Fort Collins. At thirtieth year, the system can deliver 7.8Ć10ā¶ mĀ³/year of water (6.4Ć10Ā³acre-ft/year) in an average year and up to 15.7Ć10ā¶mĀ³/year of water (12.7Ć10Ā³acre-ft /year) in a drought year. The estimated present value cost from deterministic and stochastic models of the entire project was $ 23.1 million U.S and $ 22.5 million U.S., respectively. Not considered in the cost analysis is the value of the water saved due to reduced losses of evaporation and seepage losses, inherent with surface water storage. The model shows high reliability in meeting demand through the lifespan of the project, with no failure anticipated. The deterministic model added 9.12 million mĀ³ to the aquifer, while the stochastic model shows an average addition of 16.8 million mĀ³ to the aquifer. Greater stored water with the stochastic model is attributed to less pumping of groundwater. Further study is needed to resolve the basis for the stochastic model pumping less groundwater. The capital cost of the project is predicted to be approximately $ 6.0 million U.S. by both models. Both models estimated the need for 10 ASR wells and two alluvium inflow drain units through the lifespan of the project. The case study of Fort Collins shows the potential of subsurface water storage as a viable and cost effective alternative to surface water storage.Item Open Access The development of a simplified asset management model for fixed US Air Force installations(Colorado State University. Libraries, 2014) Gregory, Colby S., author; Grigg, Neil, advisor; Bailey, Ryan, committee member; Glick, Scott, committee memberWater utility infrastructures that support Air Force installations are not only important to but also expensive to maintain and repair. While the Air Force strategic asset management structure focuses on mid- to long-term planning for budget allocation, at the installation level many issues confront the effectiveness of this program. Problems arise at every level within the installation's utility asset management program from asset inventory to condition assessments and failure consequence assessment. With inaccurate asset inventories, data disparities and uncertain information on system condition, installations are forced to take a "worst first" approach to maintenance operations. The largest issues confronting utility management at the installation level are time and money. Reductions in force size and spending provide the impetus to create a simplified method for asset management. To solve this complex problem, an investigation of various approaches to utility asset management has been conducted to encompass the intent of the Air Force's existing activity management framework. Using pre-existing information and new methods, a risk management model was developed to bolster the efficacy of the pre-existing management system. Knowledge-based condition assessments and criticality assessments allow utilities engineers to calculate infrastructure risk for their planning horizons, rather than strategic planning horizons. This research includes analytical and mathematical approaches that formulate the backbone of the simplified process. This study also provides a user-focused data model and an implementation strategy to outline the processes required to improve management conditions. By laying the groundwork for how utility infrastructures can be better managed, conclusions about feasible approaches are made considering the Air Force's monetary and manpower constraints. The research was validated through a case study at Francis E. Warren Air Force Base. A discovery was made that through both a paradigm shift in the calculation and communication of failure consequences, improvements can be made to the process by which infrastructure is managed at the installation level. The research concludes with an analysis of the roles of key factors in the process of asset management as practiced by the defense industry and fee-based public utilities. The implications of this research primarily benefit multi-layered organizations that currently use a top-down approach to asset management. By aiding the ability for lower levels to aggregate data and determine priority, improved levels of service, more effective mission support and reduced outages may be realized.Item Open Access Thermal monitoring of natural source zone depletion(Colorado State University. Libraries, 2019) Karimi Askarani, Kayvan, author; Sale, Thomas, advisor; Ham, Jay, committee member; Scalia, Joseph, committee member; Bailey, Ryan, committee memberNatural Source Zone Depletion (NSZD) has emerged as a viable remedial approach for mature releases of petroleum liquids in soils and groundwater. Herein, petroleum liquids in soils and groundwater are referred to as LNAPL. In recent years, gradient, dynamic chamber, and carbon trap methods have been developed to quantify NSZD rates based on measuring the consumption of O2 or the generation of CO2 associated with biodegradation of LNAPL. A promising alternative approach to resolving LNAPL NSZD rates is real-time monitoring of subsurface temperatures. Transformation of temperature data to NSZD rates involves use of background-corrected temperature data, energy balances to resolve NSZD energy, and an estimate of heat produced through NSZD. All current computational methods for quantifying NSZD rates using temperature data have the drawbacks of: 1) incomplete energy balances 2) ignoring the effect of water table fluctuation, and 3) using linear extrapolations of temperature profiles to calculate thermal gradients. A regression algorithm is advanced to overcome the primary drawbacks of current computational methods that convert subsurface temperature data to NSZD rates using background correction. The regression algorithm is demonstrated using 42 million temperature measurements from a fuel terminal. An 8% difference between NSZD rates from the CO2 Trap method and the regression algorithm supported the validity of regression algorithm for estimation of NSZD rates using subsurface temperatures. In addition, seasonal behavior of NSZD rates is captured and correlated water content in shallow soils and depth to the water table. It is concluded that as the water table rises, the apparent NSZD rates increase, while larger water content in shallow soil causes a reduction in the apparent NSZD rates. Imperfection with background-correction approaches can be attributed to many factors, including differing infiltration of precipitation, vegetative cover, soil properties, and net solar radiation, at background versus impacted locations. Differences between the background location and the impacted area cause anomalous background-corrected temperatures leading to over/under estimation of NSZD rates. A new computational model is developed to eliminate the need for background correction of temperature data in calculating NSZD rates. Since the new model uses only the temperature data collected from the temperature sensors attached to a single solid stick, the model is referred to as the "single stick" method. The validity of the single stick model is evaluated using a numerical model and field temperature data. Agreement between the results from a numerical model with imposed heat fluxes, and estimated heat fluxes using temperature data derived from the numerical model, supports the validity of single stick model. In addition, a close match between single stick simulated temperatures using estimated heat fluxes and actual measure temperatures supports the validity of the single stick model. Furthermore, comparison of NSZD rates from the single stick model with the rates from background correction methods at background locations shows that the single stick model is the only algorithm that consistently provides near zero NSZD rates in clean areas. Lastly, per thermodynamic calculations and preliminary lab studies, it is observed that negative NSZD rates may be due to endothermic methanogenic process. Thermal conductivity is one of the key input parameters for all computational methods converting temperature data to NSZD rates. An integrated Internet of Things (IoT) instrument and computational model is developed to measure real-time in-situ thermal conductivity of soils. Favorable agreement between measure ex-situ and in-situ thermal conductivities values supports the validity of the demonstrated in-situ techniques for estimating thermal conductivities. Favorable attributes of the new in-situ methods include lower cost, automated data acquisition and an ability to acquire in-situ estimates of thermal conductivities through time. Overall, this work demonstrated that monitoring subsurface temperature is a viable technique to resolve NSZD rates for LNAPLs. A promising next step for evaluating the validity of thermal NSZD rates is to periodically collect and analyze cryogenic cores from field sites to independently validate NSZD rates. Also, further work is needed to better resolve NSZD thermodynamics.Item Open Access Trends and controls on lake color in the high elevation western United States(Colorado State University. Libraries, 2021) Austin, Miles T., author; Ross, Matthew R. V., advisor; Hall, Ed, committee member; Bailey, Ryan, committee memberLakes are perceived to be having an increase in algal blooms across the Western United States due to climate change driven and other anthropogenic drivers. Despite this perception, long-term records do not exist for many lakes, so looking at macroscale patterns is challenging. We present and discuss here our results from using a remote sensing dataset, LimnoSat-US. LimnoSat-US contains Landsat imagery from 1984 to 2020. In the intermountain west, our focus study region of Colorado, Wyoming, Idaho, Montana, New Mexico, and Utah, LimnoSat includes 1,200 lakes and over 150,000 summer observations of water color and reflectance. We used LimnoSat-US to examine what controls lake color and what, if any, changes are occurring lake color, which is a strong indicator of whether a lake is prone to algae blooms. A lake's mean depth and annual temperature were the strongest predictors of whether a lake was, on average, blue and clear or green and murky. Despite the perception of increased algae blooms, we found no consistent evidence of lakes 'greening' or shifting from mostly oligotrophic, blue, and clear to eutrophic, green, and murky. Instead, the vast majority of our lakes (> 80%) had no trend in lake color. Further, we found that our approach did not capture the dominant controls on whether not a lake was shifting from blue to green or green to blue, highlighting the need for additional work.Item Open Access Vulnerability of U.S. river basins to water shortage over the 21st century(Colorado State University. Libraries, 2021) Heidari, Hadi, author; Arabi, Mazdak, advisor; Warziniack, Travis, committee member; Brown, Thomas C., committee member; Bailey, Ryan, committee member; Goemans, Christopher G., committee memberFuture changes in climate and population across the United States may cause a decrease in freshwater availability and an increase in water demand. These trends may lead to more frequent water shortage conditions when water demand exceeds water supply. The enhanced characterizations of changes in both longāterm anomalies such as aridity and evaporative indices and short-term anomalies such as multi-year and interannual water shortage events in a changing environment are requisite to the appropriate management and planning of future water resources, and improved implementation of regional adaptation and mitigation strategies. The main goal of this dissertation is thus to assess shifts in hydroclimatic conditions and water shortage (IDF) relationships across the conterminous United States (CONUS) over the 21st century. To achieve this goal, first, the effects of climate change on the regional hydroclimatology of U.S. river basins were assessed over the 21st Century to determine regions with prolonged dry or wetting periods. This analysis shows that U.S. river basins within the CONUS can be clustered into seven groups with unique hydroclimatic behaviors in response to climate change that are highly associated with regional landform, climate, and ecosystems of river basins. The South United States is more likely to experience warmer and drier conditions meaning higher chances of aridification. Second, the impact of climate change on hydroclimatic conditions of U.S. national forests (NFs) and national grasslands (NGs) was investigated. The results of this study indicate that NFs and NGs are more likely to experience larger changes in hydroclimatic variables compared to the average of the United States. The findings help environmental scientists and forest managers to mitigate the negative consequences of climate change on forest and grassland resources. Third, shifts in hydroclimatology of U.S. megaregions in response to climate change were investigated. This analysis reveals that Houston may experience more arid climatic conditions with higher evaporative loss of freshwater resources in the future. These steps provide an improved understanding of the effects of climate change on the regional aridification or desertification across the CONUS. To accomplish the goal of the study, fourth, a probabilistic approach was developed to improve the characterization of both within-year and over-year socioeconomic droughts in a changing environment. The proposed approach provides a procedure to update sub-annual socioeconomic drought IDF relationships while taking into account changes in water supply and demand. Fifth, the developed probabilistic approach was applied to examine the effects of urban development patterns, i.e., sprawl versus high-density development, on the socioeconomic drought characteristics. The results of this study highlight that urban regions under the sprawl development pattern are likely to experience more frequent socioeconomic drought events with higher intensity and longer duration compared to the high-density development pattern. Finally, the developed approach was implemented across the CONUS to characterize vulnerability of U.S. river basins to water shortage from 1986-2015 to 2070-2099 periods. The results show that prolonged water shortage conditions in drier basins and interannual water shortage events in wetter basins are likely to be the main concerns in the future and should gain more attention in future water resource planning and management.