Theses and Dissertations

Permanent URI for this collectionhttps://hdl.handle.net/10217/100381

Browse

Now showing 1 - 20 of 685

Open Access
Design of baffled hydraulic jump stilling basins for dams
(Colorado State University. Libraries, 2025) Moses, Dana Wesley, author; Thornton, Christopher, advisor; Crookston, Brian, committee member; Ettema, Robert, committee member; Julien, Pierre, committee member; Rathburn, Sara, committee member
The hydraulic jump has been studied and used as a primary means of energy dissipation for hydraulic structures for well over a century. By the 1920s and 1930s, baffled hydraulic jump stilling basins were in widespread use as energy dissipators for large dams. These hydraulic jump stilling basins often consisted of toe blocks, a negative step and/or toe curve; one or more rows of baffle blocks; and a solid or dentated end sill. By the 1950's standard design guidance was developed by multiple agencies and universities. A comparison of the standard baffled hydraulic jump guidance illustrates a drastic difference in recommended stilling basin geometry with identical incoming flow conditions. For example, given the same incoming flow conditions, the height of baffle block determined for a U.S. Bureau of Reclamation standard design can be more than twice the block size for a standard outlet works stilling basin determined from US Army Corps of Engineers guidance. The use and/or geometry associated with chute blocks, number of rows of baffle blocks, length of basin, distance to baffle blocks, and end sill geometry have similar discrepancies. The current research includes a systematic physical model evaluation, performing over 400 individual experiments of the most often utilized baffled stilling basin design configurations. These experiments include 15 stilling basin configurations, each being evaluated for six discharge conditions and six tailwater scenarios. In addition, the USACE standard stilling basin configuration was evaluated for the general scour tendencies for discharges below and above the design discharge by means of mobile bed physical modeling. A numbered list of significant findings associated with the current research are provided below. Detailed descriptions of these significant findings and other conclusions and recommendations associated with the research objectives are provided subsequently. 1. The USACE (1992) stilling basin configuration is recommended for incoming Froude Numbers less than 4.5. 2. The Modified Type III stilling basin configuration is recommended for incoming Froude Numbers in the range of 4.5 to 8. 3. The stilling basin length and minimum required tailwater for the USACE (1992) and USBR (1984) can be expressed by unified equations. 4. A toe curve is not recommended for the hydraulic jump basin due to increase in length required and the decrease in jump stability. 5. Intermittent ramps associated with the tapered baffle block configuration are not recommended due to increase in downstream scour potential, decreased tailwater resilience, cost, general lack of observed cavitation damage, and unproven effectiveness in reducing cavitation damage. 6. Macro-scale turbulent structures exiting the stilling basin are the primary phenomenon controlling downstream scour potential. A maximum downstream attack angle of 15-degrees from horizontal was determined for the USACE (1992) stilling basin configuration for incoming Froude Numbers in the range of 3 to 5.
Open Access
Novel applications of data-driven approaches for understanding the impacts of household energy interventions
(Colorado State University. Libraries, 2025) Brehmer, Collin, author; Carter, Ellison, advisor; Davenport, Frances, committee member; Keller, Kayleigh, committee member; Sharvelle, Sybil, committee member
Air pollution from household solid fuel combustion is associated with premature death, disease, and radiative climate forcing. Beginning in 2015, the Chinese government implemented the Clean Heating Policy in Northern China (CHP) with the goal to transition 70% of homes in the Beijing region from coal-based space heating to natural gas or electric-powered space heating. Studies of the impact of the CHP on air pollution and the potential mechanisms of action are limited. The continued use of a secondary solid fuel or heating device after the primary solid fuel heating stove is replaced with a cleaner alternative could weaken the impacts of the effort to replace the primary solid fuel stove. In Chapter 1, we identified heating events from biomass kang stoves as a proxy for stove use using a combination of manually labeled data and XGBoost modeling. We showed that biomass kang stove usage did not change because of the CHP and agreed with self-reported measures of heating duration. Our results demonstrated the capability of XGBoost to identify stove use events when trained on manually labeled event data and provided evidence that self-reported measures of stove use may be sufficient for understanding how secondary stove use changes as a result of a household energy intervention. Fine particulate matter air pollution (PM2.5) is of particular interest when evaluating household energy transitions since it is a product of incomplete combustion and is related to several health outcomes. We evaluated the impacts of the CHP on seasonal indoor, seasonal outdoor, and 24-hr personal PM2.5 exposure in 50 villages, 300 homes, and 500 participants during three years over a four-year period. The CHP had high uptake, with a significant decrease in coal usage in treated groups. We also observed a significant reduction in seasonal average indoor PM2.5 (22.2 [4.2, 40.3] µg/m3). Seasonal outdoor and 24-hr personal PM2.5 exposure did decrease over time but the decrease could not be attributed to the CHP due to similar decreases in treated and untreated groups. Our study suggests that the CHP yielded promising results in reducing indoor PM2.5 and provided valuable insights for household energy transitions worldwide. Given that most household energy interventions target one source of air pollution, using a mixture of sources as an outcome, like PM2.5, when only one of the sources of air pollution is targeted by the policy can make it hard to disentangle the effects of the policy if the variability in the non-targeted sources is high. Chapter 3 identified sources and their contributions to outdoor and personal PM2.5 exposure using chemical analysis and source apportionment. We used the concentration of the coal-containing source in outdoor and personal exposure measurements as the outcome in policy analysis models and compared the findings to the models where total PM2.5 was the outcome. We found a significant reduction in personal exposure to the coal containing source (-7.75 [-13.4, -2.14] µg m-3), which contrasts with our findings that the CHP had no impact on personal exposure to total PM2.5. This work demonstrates how additional granularity in the air pollution outcome can serve as a better outcome than a mixture of sources.
Open Access
Development of data integration strategies to improve interdisciplinarity in hazards research
(Colorado State University. Libraries, 2025) Johnston, Blythe, author; van de Lindt, John W., advisor; Guo, Yanlin, committee member; Mahmoud, Hussam, committee member; Shields, Martin, committee member
Natural hazards are inherently interdisciplinary problems that pose risk to human life, property and prosperity. To provide holistic and actionable solutions in the face of these hazards, a more integrated approach to hazards research is needed. The current state of the hazards and disaster research continues to work more in disciplinary silos with progress being made around the world. This progress is ongoing, and this dissertation contributes to the investigation of these cross- and trans-disciplinary spaces in the context of natural hazards research and how they can be further fused and progressed, with a specific focus on data integration and modeling techniques that inform the complex problem of outmigration characterization following a hazard event. For contextualization, this dissertation first presents prior attempts at data integration. With the commonly echoed best practice of data integration from the earliest stages of data creation, a set of tools are developed for more interdisciplinary data collection in geographically large field studies. These tools are then implemented for the creation of a multi-community dataset tracking damage and recovery following the December 2021 Midwest Tornado Outbreak. This data can be utilized in the training and parameterization of long-term post-event models such as outmigration prediction. Modeling techniques for using the knowledge and data acquired in this field study are explored to arrive at actionable and predictive data for enhanced interdisciplinary hazards research. These modeling techniques include the combination of top-down and bottom-up approaches, linear multi-regression modeling, agent-based modeling, and hindcasting. Some or all these techniques are used to first develop a sheltering model to determine the viability of community tornado shelters during an event similar to that seen in the field study, and establish the knowledge needed to undertake the more complex outmigration model. The datasets and modeling techniques created and acquired are then leveraged to develop a top-down and bottom-up outmigration model after a hazard event that predicts rate of gross outmigration, gross inmigration, net migration, and demographic change following a hazard event. With this set of tools and resources, this dissertation aims to tangibly propel the task of interdisciplinarity in disaster and natural hazards research with the set of tools and resources provided here culminating in the development of a model for predicting long-term population flow following an event.
Embargo
Examining social equity in transportation asset management: current status and integration approaches
(Colorado State University. Libraries, 2025) Khalife, Fawzi Ghazi, author; Atadero, Rebecca, advisor; Ozbek, Mehmet, advisor; Grigg, Neil, committee member; Arneson, Erin, committee member; Malin, Stephanie, committee member
Transportation is a critical component of the built environment, vital for ensuring access to essential services and opportunities. In the U.S., transportation systems have expanded significantly since the rise of the automobile and the development of the Interstate Highway System. While these advancements have enhanced connectivity and accessibility, they have also had detrimental effects on many communities. Research shows that low-income and racially minoritized groups are disproportionately impacted by displacement, pollution, and substandard transportation infrastructure. This disparity has raised concerns about social equity among transportation professionals, which commonly refers to the fair distribution of benefits and burdens associated with transportation systems. Transportation asset management (TAM) is one subsector of transportation where social equity remains overlooked. TAM is centered on the operation and maintenance of transportation systems, traditionally prioritizing economic factors while giving minimal attention to social and equity factors in decision-making. To address this issue, this dissertation explores the integration of social equity – referred to as equity in this study – within TAM, identifies strategies for effectively incorporating equity into TAM practices, and analyzes the challenges faced in this process. This research is organized into three studies designed to highlight equity-related issues in TAM and promote the integration of equity into TAM practices. The first study (Chapter 2) investigated the incorporation of equity within TAM by analyzing the 2019 TAM plans from all U.S. states. The findings revealed that equity remains neglected in these plans, with many in the sector failing to integrate equitable practices. This underscored the need for further research on equity in the context of TAM. Additionally, the study reviewed existing guides and sustainability rating systems that can assist in managing assets to promote equity. These resources provide definitions and indicators of equity that TAM professionals can utilize as a foundation, allowing them to adapt and expand upon these frameworks to address the specific needs of their communities and achieve equitable outcomes. The second study (Chapter 3) involved conducting interviews with professionals engaged in integrating equity into transportation to gain deeper insights into the challenges they encounter. Recognizing that transportation sectors outside of asset management have made greater progress in integrating equity into practice, this study included a diverse sample of 29 professionals from local governments, community-based organizations, and departments of transportation. This approach reflects the varied backgrounds and expertise of those engaged in equity work within the transportation sector. Utilizing semi-structured interviews and thematic analysis, the author categorized equity-related challenges into four themes: definitions, metrics and data, community engagement, and organizational challenges. This research enhances the understanding of these challenges and explores strategies for effectively addressing them, facilitating the successful integration of equity across various transportation sectors, including TAM. The third study (Chapter 4) surveyed TAM engineers and professionals to understand whether and how equity is currently incorporated in their practices and decision-making processes. The respondents provided information about their work in TAM and equity, sharing their expert opinion on equity-related issues. The findings indicated that while equity remains neglected within TAM, there are existing efforts and initiatives that could be enhanced to promote equity. Respondents noted that there is not a singular approach to advancing equity in TAM and that several challenges hinder the process, particularly in measuring equity, securing funding for equity programs, and defining equity in the context of TAM. This understanding of equity in TAM can empower TAM professionals to better understand and advance equity in their work. This dissertation offers a deep understanding of equity in the context of transportation and TAM. It concludes by offering insights and resources that enable engineers and professionals in TAM to define and measure equity in their work, implement actionable strategies, and develop plans to advance equity while managing associated challenges. The findings aim to assist TAM professionals in refining their practices to better address community needs and deliver equitable outcomes, ultimately advancing social justice through transportation infrastructure and assets.
Open Access
Evaluating personal PM2.5 and black carbon exposure variability in Beijing's rural communities
(Colorado State University. Libraries, 2025) Hirst, Kennedy, author; Carter, Ellison, advisor; L'Orange, Christian, committee member; Bareither, Christopher, committee member
Exposure to air pollution is a major public health concern, with PM2.5 and black carbon (BC) linked to adverse health outcomes. To reduce emissions of PM2.5 and BC, the Chinese government implemented the Coal-to-Clean Energy Policy (CCEP) in 2016, reducing indoor PM2.5 concentrations. However, its effect on personal exposure remains unclear. This study evaluated the role of time-activity patterns in personal exposure to PM2.5 and BC in the context of the policy. Data from the Beijing Household Energy Transition study (winters of 2018-2022) included 252 participants with concurrent indoor and personal PM2.5 measurements and GPS- based time-activity data. Geofencing classified participant locations, and generalized linear models assessed exposure determinants. Model performance was evaluated using indoor PM2.5 data with and without time-activity adjustments. Personal PM2.5 exposure averaged 52.9 μg/m3, while BC averaged 1.6 μg/m3. The best PM2.5 model used indoor PM2.5 over the full sampling period (AIC: 489.06, adjusted R2: 0.59). The top BC model used indoor PM2.5 averaged only while participants were home (AIC: 407.59, adjusted R2: 0.25). On average, participants spent 20.0 hours at home per day (95% CI: 19.4, 20.7). Despite these time-activity trends, the lack of reductions in personal exposure were not explained by time-activity patterns, indicating that other influential factors may be impacting exposure, or the available data was insufficient to fully capture exposure variability. Enhanced time-activity monitoring is necessary to improve exposure assessments and better inform air quality interventions.
Open Access
Evaluating sources of volatile organic compounds in Colorado workplaces via positive matrix factorization
(Colorado State University. Libraries, 2025) Lippmann, Jadelyn, author; Carter, Ellison, advisor; Burt, Melissa, committee member; Atadero, Rebecca, committee member
Recognition of the health risks associated with exposure to volatile organic compounds (VOCs), particularly in indoor environments, has increased the need for a stronger understanding and management of air quality. Exposure to VOCs, emitted from various sources like building materials, office equipment, and consumer products, have been linked to both acute and chronic health outcomes, including respiratory issues and carcinogenic effects. While research on residential indoor air quality is extensive, fewer studies have characterized VOC exposure, particularly in workplaces, where people may spend a significant portion of their time. The work presented in this thesis addresses this knowledge gap through analysis of a comprehensive empirical study of VOC concentrations in 50 diverse workplaces across the State of Colorado. The study presented herein, which is part of a broader initiative led by Colorado State University in partnership with the Colorado Department of Public Health and Environment (CDPHE), utilized weeklong air sampling with SUMMA canisters and analyzed 61 target VOCs via EPA Method TO-15. Positive Matrix Factorization (PMF) modeling was employed to identify and apportion the sources of VOCs, providing insights into the relative contributions of indoor and outdoor pollutants. The findings inform further understanding of patterns of indoor VOCs measured in workplaces, as well as the design and implementation of targeted interventions to improve indoor air quality in occupational settings, particularly in underserved communities. Ultimately, this work contributes to advancing exposure science and supports healthier, and more sustainable indoor environments where people work.
Embargo
GeoStable Tailings laboratory mixture trial
(Colorado State University. Libraries, 2025) Jagerhorn, Emily Clarice, author; Scalia, Joseph, IV, advisor; Bareither, Chris, advisor; Sanford, William, committee member
This study focused on GeoStable Tailings, a homogeneous mixture of tailings and waste rock. The research evaluated (i) the influence of laboratory placement methods on mixture dry density and (ii) the influence of mixture characteristics (mixture ratio and tailings solids content) on hydraulic and mechanical behavior of GeoStable Tailings. Laboratory testing was conducted to assess dry density, air permeability, penetration resistance, and slump for different GeoStable Tailings mixture ratios, tailings compositions, solids contents, and placement methods. Standard Proctor compaction, drop chute, and loose placement methods were used to represent a range of compaction energies. Placement of GeoStable Tailings with standard Proctor compaction yielded specimens that were more consistent in the engineering behavior, whereas specimens placed via the drop chute or loose placement were more variable. Results indicate that standard Proctor compaction produces more consistent engineering behavior, whereas drop chute and loose placement exhibit greater variability. Whole tailings with solids contents above 80% and mixture ratios between 1.0 and 2.0 demonstrated optimal performance in minimizing air permeability, ensuring trafficability, and maintaining structural integrity. Underflow tailings exhibited a broader range of viable mixture ratios and solids contents, with enhanced stability and reduced deformation potential. Findings from this research contribute to the development of practical design guidelines for field applications of GeoStable Tailings, supporting the integration of tailings and waste rock as a sustainable alternative to traditional tailings management.
Open Access
Numerical model of sediment transport in sediment bypass tunnels: influence of transverse slope in tunnel bend
(Colorado State University. Libraries, 2025) Brown, Jesse, author; Thornton, Christopher I., advisor; Ettema, Robert, advisor; Dumitache, Ciprian, committee member
Sediment Bypass Tunnels (SBTs) convey sediment around reservoirs, increasing reservoir lifespan by greatly reducing reservoir sedimentation and, thereby, mitigating consequent loss of reservoir water-storage capacity. To keep SBTs small and economical in cross-section, SBTs convey super-critical flows. Consequently, SBTs convey super-critical flows with large sediment loads, typically containing high concentrations of coarse particles of sediment that can cause abrasion of SBT liners. Especially vulnerable are SBT reaches where secondary currents develop, notably SBT bends. The sediment abrasion that occurs along the invert of a bend requires expensive, frequent replacement of the invert's concrete liner. Consequently, the abrasion rate of inverts and, therefore, bend flow fields are of interest to SBT designers. SBT design variables such as sediment-size distribution, invert-liner type (usually concrete), flow cross-section dimensions, tunnel slope and bend radius can affect sediment abrasion in an SBT, doing so by influencing flow field, secondary currents, and patterns of sediment abrasion. This study focuses on sediment abrasion of SBTs:1. The flow field generating secondary currents associated with free-surface flows along SBT bends; and 2. Banking of an SBT invert to reduce sediment abrasion. The concept of invert-banking was proposed in personal communications with Dr. Ismail Albayrak of the Federal Institute of Technology (ETH), Zurich, Switzerland. The concept was floated during a SBT site inspection in April 2024. The problem of sediment abrasion is a problem for hydraulic structures in mountainous regions such as Switzerland and parts of the United States (e.g., Muller-Hagermann et al. 2020; Melesse et al. 2023). The present study uses the Computational Fluid Dynamics (CFD) code OpenFOAM to create a numerical model of an existing SBT for which hydraulic-model and field data and observations exist. The numerical model was used with the solver interFoam, and the renormalization group (RNG) k-ε turbulence flow assumption, the volume of fluid (VOF) method, and a Discrete Element Model (DEM) coupling. Of focal interest in the modeling was the pattern of secondary flow in a bend whose invert had variable transverse sloping. The prototype bend selected for this study is Switzerland's Solis SBT. The pattern of secondary flow in the bend affected the distribution of sediment across the bend's invert and, therefore, the sediment abrasion experienced by the bend. The Solis SBT, part of the sediment control system used for Solis Reservoir, was chosen for this study because of data and observations availability. Built in 2012, the invert of a bend in the Solis SBT has experienced severe abrasion owing to sediment. This study recommends a small amount of banking in the Solis SBT and other tunnels with similar hydraulic properties. Even a 1% to 2% slope appears to have a substantial effect in distributing the sediment evenly.
Open Access
Geomorphic impacts of large wood restoration in an urban Colorado stream
(Colorado State University. Libraries, 2025) Schoner, Bijoux, author; Morrison, Ryan, advisor; Rathburn, Sara, committee member; Alves Meira Neto, Antônio, committee member
The effects of urbanization on river systems lead to degradation and simplification, reducing beneficial ecosystem functions. Prior to urbanization, many rivers in the Mountain West were geomorphologically complex, hydrologically interconnected, interspersed with large wood, and connected to their floodplains, providing numerous ecosystem services that led to functional resilience. Process-based restoration techniques are being implemented to reintroduce and support these lost functions in both rural and urban areas as an alternative to form-based restoration. Minimal research around process-based techniques has been done in urban systems and understanding how this approach impacts geomorphic response in varied biomes provides practitioners a basis to evaluate future projects. The objective of this study is to analyze the effects of a large wood process-based restoration in an urban Colorado corridor (Cache la Poudre River, Fort Collins, CO) by monitoring changes in 1) site erosion and deposition, 2) geomorphic unit heterogeneity, 3) large wood volume and porosity, 4) evaluate whether monitoring geomorphic units is an adequate metric of project success, and 5) to compare restoration techniques throughout the site by analyzing sediment changes. Additionally, I review and recommend monitoring methodologies and discuss how water policy affects restoration in Colorado. The site restoration included reconnecting the floodplain, reconstructing site bathymetry, and adding large wood to both the floodplain and active channel. Following restoration construction and one runoff season, digital elevation models were analyzed to delineate geomorphic units and compare restoration approaches. iPad LiDAR was collected at six constructed large wood structures to determine volumetric and porosity changes. Sediment analysis shows net aggradation of sediment around structures, supporting the project goal of mitigating an impending head cut. Large wood analysis results varied based on structure location within the channel and with respect to other large wood structures. The accumulation and dispersion of wood throughout the site was captured by newly formed islands induced by restoration. Both the largest patch index and patch density heterogeneity metric either stayed consistent or increased after the runoff season. This restoration project demonstrates to policymakers the geomorphological, ecosystem, and social benefits while showcasing the low-risk nature of carefully designed process-based restoration using large wood. Greater utilization of large wood in urban restoration more broadly supports the ecosystem services that benefit the communities that live in and around the river.
Open Access
Ex post facto analysis of the Sedgwick Sand Draws Project: a case study of the small watershed program
(Colorado State University. Libraries, 1999) Ward, Jason P., author; Ruff, James, advisor; Grigg, Neil, committee member; Wilkins-Wells, John, committee member
The Sedgwick Sand Draws Project is a flood control project completed in 1992 to provide floodwater damage protection for agricultural and municipal lands in Sedgwick County, which lies in extreme northeastern Colorado along the South Platte River. Funding and technical support for the project was provided by the U.S. Soil Conservation Service (SCS) under the Watershed Protection and Flood Prevention Act, commonly referred to as The Small Watershed Program. Short duration, high intensity thunderstorms occur in mid to late summer in the upland portions of the Sand Draws Watershed near the Colorado- Nebraska border. Runoff from these storms is channeled into upland sand draws that drain into the developed alluvial floodplain below. Before project average annual floodwater damages were estimated at $220,050. An ex post facto method was proposed for evaluating the damage reduction benefits of a watershed flood control project. Using economic, hydrologic and engineering principles, damage-frequency curves developed in the proposal phase of a project are used to estimate actual damage reduction benefits. Estimates are made by adjusting the damage-frequency curves to reflect a current economic time base and evaluating damages produced by hydrologic events that have occurred during the period of analysis. Other performance indicators, such as site inspections, historical crop yields, changes in land use, disaster relief application rates, and interviews with local community members are also used in the evaluation. The ex post facto evaluation principles were applied to the Sand Draws project as a case study. However, lack of information in the SCS Sand Draws proposal required a technique for estimating the original damage-frequency curves. A method for estimating the curves from minimal known information was developed and used for the Sand Draws project. The period of analysis was from completion of the project in June 1992, to the latest date of available data, September 1997. Hydro logic analysis of the watershed identified seven damage producing rainfall events during this period. It was estimated that the project has produced a total of$3,556,628 in damage reduction benefits resulting in average annual benefits of $592,771. Benefit-cost analyses and a look at other performance indicators were also evaluated.
Open Access
Development of the piezovane for estimating liquefaction potential of saturated sands
(Colorado State University. Libraries, 1994) Butler, Leo Wm., author; Charlie, Wayne A., advisor; Siller, Thomas J., committee member; Doehring, Donald O., committee member
The Piezovane was developed for determining in situ liquefaction potential of saturated sands by measuring the porewater pressure response oi saturated sand during and after shearing of the soil. A negative porewater pressure response is an indication that the material is in a dense (dilative) state; therefore is not susceptible to liquefaction failure. Positive porewater pressure response is an indication that the sand is in a loose (contractive) state and is susceptible to liquefaction-type failure. This project included design, fabrication of the Piezovane apparatus and the calibration chamber for the initial laboratory testing. Sands were placed within the calibration chamber at densities greater than or less than densities at the steady state which had been developed by using CU triaxial and CD direct shear tests. Trends indicate that the Piezovane testing can predict contractive or dilative behavior of soils. Additional testing both in the laboratory and in the field is required to determine whether these measured porewater pressure responses and measured shear resistances provide parameters needed for evaluating liquefaction potential and their possible use for design. A patent for the Piezovane has been awarded.
Open Access
Estimating liquefaction potential of sands using the piezovane
(Colorado State University. Libraries, 1989) Scott, Clinton E., author; Charlie, Wayne A., advisor; Doehring, D. O., committee member; Siller, T. J., committee member
Laboratory test results are presented indicating feasibility of estimating liquefaction potential of saturated cohesionless soil using the piezovane, a shear vane incorporating pore pressure measurement. Utilizing a calibration chamber, piezovane shear tests are conducted on medium-fine subrounded quartz sand. Partially drained tests show small negative pore pressure peaks in dense samples and small positive peaks in relatively loose samples, indicating a reasonable trend of volumetric strain tendencies during shear. The piezovane induces positive pore pressure at denser initial states than steady states (zero contraction) determined by CU triaxial tests, but peak shear strength trends and direct shear test results indicate that observed pore pressure response adequately reflects actual contractive and dilative tendencies during piezovane shear.
Open Access
Synthesis of design operation and management of surface irrigation conveyance systems
(Colorado State University. Libraries, 1984) Sritharan, Subramaniaiyer, author; Richardson, E. V., advisor; Clyma, Wayne, advisor; Fontane, Darrell G.. committee member; Sunada, Daniel K., committee member; Hall, W. A., committee member
A theory for the design of conveyance systems, synthesizing with it the operation and management and set in an interdisciplinary mode is proposed. The theory involving eleven steps is required in the development of solutions to six basic problems hitherto inadequately addressed. These solutions are given in the following six modules of the dissertation: (i) Optimal Turnout Area Module, (ii) Turnout Area Water Requirement Module, (iii) Project Scale Farm Design Module, (iv) Ground Water Interaction Module, (v) Water Issue Strategy Module and (vi) Hydraulic Simulation Module. The problem of optimal turnout area was studied using causal processes theory (of mathematical sociology). Independence models and first order Markovian dependence models describing farmer behavior in the turnout area were studied. The turnout area water requirement problem was studied using a probability based design evapotranspiration computation procedure. Requirement depths were obtained by deriving optimal scheduling in space and time applying dynamic programming, using recent crop production functions and considering recent soil moisture stress models. Water requirements in terms of depth were converted to flow requirements in an optimal manner considering the hydraulics of the application system again using a two stage programming approach. Requirement efficiency and deep percolation ratio functions were developed for level borders using a zero-inertia model for four different soil types and for furrows using SCS approaches for the use in the model. Ground water interactions in the irrigated areas were studied using a linearized Boussinesq equation and Green's Function approach. Recharge excitation was represented by a finite Fourier series fitted to the excitations obtained using the developed deep percolation functions and the appropriate boundary conditions. Long term water table build up was studied using this approach for any detrimental effects due to application system design. Different water issue strategies and their optimality/acceptability were studied. The optimal strategy for a Rotational Water Issue (RWI) was that the rotations be as low in the hierarchy of the canal system as possible and the capacities depended on the irrigation intervals. The problem of hydraulic simulation was studied using the linearized diffusive wave equation for canal flow. The integral method was found to compare well with the analytical solution and was used for the solution of the advance problem. Delay times in releasing fixed steps of flow were computed using this approach. The operational criteria and necessary control measures were developed. The solution procedures were applied to a sample hypothetical project area and found to be applicable.
Open Access
Environmental impact and limnological response of a deep wastewater treatment pond
(Colorado State University. Libraries, 2000) Mohsin, Syed Ali, author
The annual and seasonal response of water quality variables to the annual hydrometeorological variation is evaluated at the 10 ft. deep wastewater treatment pond no. 3 of Boxelder Sanitation District. Data of six water quality variables are collected, in one foot depth increments from the surface to the bottom of the pond, to investigate their temporal and spatial response to the seasonal variations in maximum-monthly solar radiation, air temperature, and peak wind gusts. Discrete Fourier series of the nine hydrometeorological variables are generated to study the maximum response of the water quality variables to changes in hydrological phenomena at the surface of the pond.
Embargo
Analysis of municipal water use in urban regions across the contiguous United States
(Colorado State University. Libraries, 2024) Dezfooli, Donya, author; Arabi, Mazdak, advisor; Sharvelle, Sybil, committee member; Carter, Ellison, committee member; Goemans, Christopher G., committee member
Urban water use in the United States faces increasing social and environmental pressures. Challenges such as population growth, urbanization, extreme weather events, and climate change threaten the balance between water supply and demand, jeopardizing access to safe and reliable drinking water for city dwellers. Additionally, the traditional linear "take-make-waste" approach, once common in addressing water-related issues, has proven unsustainable due to its reliance on finite energy and resources. Therefore, it is imperative to shift from this linear model to a more integrated and sustainable approach, known as "One Water". This shift requires a comprehensive understanding of the mechanisms enabling transitions to sustainable and resilient urban water systems, as well as the development of models and methodologies to guide the transition toward net-zero water communities. To achieve this, the dissertation first aims to deepen the understanding of factors influencing transitions towards sustainable urban water management. This is based on a series of expert interviews conducted with different utilities across North America. The qualitative data analysis provides valuable insights into the complex context of urban water management. The results revealed that achieving social and environmental justice is a prominent driver for utilities to initiate their transition, followed by concerns about climate change, water quality impairments, groundwater depletion, and population growth. Further investigations identified several barriers to the One Water transition. These barriers are not merely financial and technical but also stem from a lack of regulatory frameworks, insufficient community support, and institutional obstacles. Therefore, institutional and regulatory solutions are needed more than technological innovations to support this paradigm shift. Our findings also emphasized the importance of cultural change and the necessity of fostering a One Water mindset among stakeholders at all levels. Additionally, feedback from the participants contributed to a more comprehensive and inclusive definition of One Water. Second, a municipal water demand model was developed using the Integrated Urban Water Model (IUWM) to understand urban water use patterns and influencing factors across urban areas within the Contiguous United States (CONUS). Municipal water use data from 99 cities across the U.S. from 2005 to 2017 was used to calibrate and regionalize model parameters for urban regions across the CONUS. The results identified key factors influencing the regionalization of water model parameters, including "July vapor pressure deficit," "number of employees in other services (except public administration)," and "July precipitation." The study reveals that predictive water use and related uncertainty vary across ecohydrological regions within the CONUS. This variation is significantly influenced by climatic and socio-economic factors, with arid and southern cities showing the highest uncertainty. While densely populated areas exhibit more predictable patterns, small cities demonstrate the highest level of uncertainty in water use projections, primarily due to a higher share of single-family homes and increased outdoor water consumption compared to larger cities. Third, the developed IUWM model was used to estimate municipal water demand across urban areas within the CONUS for the period of 2035-2065 under different future climate and land use scenarios. The results indicated that population growth and land use change are primary drivers of urban water demand. While there are minor annual fluctuations reflecting the effects of different climate scenarios, the hot climate model presents the worst-case scenario, with the lowest reduction in water use intensity and the highest increase in water demand. In this scenario, the average water use demand is projected to increase by 52%, while the average water use intensity (ML/sq.km) will fall by 10%. The projected changes in water use are highly variable across the CONUS, with significant increases expected in urban areas located in the West and Northwest (e.g., Washington and California), Southwest (e.g., Arizona, Utah, Colorado, and New Mexico), Midwest (e.g., Michigan and Wisconsin), and Great Lakes region (e.g., New York and Pennsylvania). Our findings suggest that projections of future municipal water demand are surrounded by considerable uncertainties, particularly in cities located in arid and tropical regions. Furthermore, the results show that while increased urban density typically reduces water use intensity in most areas, increases are expected in parts of the Midwest, Northeast, and West. These trends suggest that once cities reach certain development thresholds (around 50% developed area), densification may no longer effectively reduce municipal water demand, leading to increased indoor and CII (commercial, industrial, and institutional) water consumption, thereby undermining the expected benefits. This highlights the need for effective mitigation strategies, such as demand management and the use of alternative water sources, alongside higher-density development policies to ensure sustainable urban water management in the future. Overall, this dissertation provides a comprehensive understanding of urban water demand in the United States, aiming to achieve sustainable urban water management. The insights gained from this study highlight the importance of integrating land use and water management and fostering collaboration among all stakeholders to achieve the One Water paradigm shift. The results will benefit urban planners and water managers, helping them develop effective strategies to mitigate adverse effects and ensure sustainable water resources for the future.
Open Access
Insights and methodologies in wall-bounded turbulent channel flows
(Colorado State University. Libraries, 2024) Mishra, Harshit, author; Venayagamoorthy, Subhas Karan, advisor; Gates, Timothy K., committee member; Julien, Pierre Y., committee member; Barnes, Elizabeth, committee member
Wall-bounded channel flows are of massive interest to civil and environmental engineers due to their immense application for water supply and management. This dissertation addresses five key aspects of turbulent channel flows relevant to practicing engineers, laboratory researchers, fluid scientists, and consultants leveraging computational fluid dynamics for modeling turbulent flows. In the first study, a device was developed and tested to enable Particle Image Velocimetry (PIV) for free surface flows. Measuring flows reliably requires that illumination provided by the laser sheet remains undisturbed. In open channel flows, introducing the laser sheet from the free surface can be necessary as the bed may be optically opaque. An oscillating free surface can further complicate maintaining an undisturbed laser sheet. This research has shown that the disturbance of the laser sheet, when introduced from the free surface, can be mitigated by introducing an improvised device called an optical coupler. The effect of the coupler on the measured velocity field was systematically studied using independent Laser Doppler Anemometer (LDA) measurements. The effect of the coupler on the measured velocity field was confined to its vicinity near the surface of the flow. The mean flow profile remains largely unaffected. Additionally, appropriate material for fabricating the coupler has been recommended by studying the relative performance of a glass and acrylic coupler. While the glass coupler measurements were closer to the undisturbed flow profile, the durability and ease of handling an acrylic coupler make it a viable alternative. The second study is focused on ensuring fully developed flow in short laboratory flumes. Ensuring a fully developed flow is essential for any experimental or modeling study that involves wall-bounded flows. Flow development in pipes has been extensively studied, and empirical relationships have been widely published. Recently, similar studies on open channels have revealed that the entrance length in laboratory flume is ≈ 100h, where h is the depth of the flow. Such a prescription renders most laboratories unfit for experimental work. Further, the inlet configuration in the flume can also hamper flow development, even after the length requirements are met. In this study, we develop a methodology to obtain developed flow in short channels by modifying the inlet and tripping the boundary layer. Further, we also provide a robust, rapid test to confirm if the flow is fully developed using Direct Numerical Simulation (DNS) datasets. The proposed method is validated using flume experiments for flows with friction Reynolds number Reτ ∼ 1500−3000. Against the current prescription, we show that it is possible to obtain fully developed profiles within a distance of ≈ 20h from the inlet. In the next (third) study, we leverage the DNS data for closed channel flow for a range of friction Reynolds Number (Reτ ∼ 180 − 5000) to develop a new One Point Friction Velocity Method (OPFVM) to calculate friction velocity U∗ in terms of free-surface velocity Um, flow depth h and kinematic viscosity ν for smooth wall-bounded flows. In contrast to prevalent methods that require several cumbersome near-boundary measurements to obtain friction velocity, the OPFVM relies on a single easy-to-measure free-surface velocity measurement. The formulation obtains friction velocity for a closed channel flow (CCF) DNS regime with Reτ = 10049 and on four open channel flow (OCF) DNS regimes with Reτ ∼ 180 − 2000. The same formulation was then experimentally verified in our laboratory. To avoid being prescriptive, a sensitivity analysis was performed to determine the permissible variation in Um to restrict the error in estimated U∗ to 2%. The relationship between the depth-averaged velocity Ub and the maximum free-stream velocity Um is also explored using the DNS datasets and an approximate relationship between Ub and Um is proposed. With advances in remote sensing technology that enables free-stream velocity measurements, this method extends the potential to measure even the friction velocity remotely. Computational Fluid Dynamics (CFD) is an essential tool for analyzing fluid flows. The k − ϵ model is a turbulence model used in Raynold-Averaged Navier-Stokes simulations to close the Reynolds stress terms. The empirical constants used in k − ϵ model were obtained using experiments conducted at low Reynolds numbers several decades ago. In this study, we revisit the turbulent viscosity parameter Cµ, based on the stress-intensity ratio c2 = |uw|k. Here, |uw| and k are the absolute values of the Reynolds stress and turbulent kinetic energy, respectively. Through a-priori comparisons, we find that the widely accepted value of Cµ = 0.09, does not agree with the latest DNS and experimental datasets of wall-bounded turbulent planar flows. Therefore, a new value is suggested by averaging c2 in the equilibrium region, where the production (P) of k is within 10% of the dissipation rate(ϵ), and consequently, c4 ≈ Cµ. We evaluate flows up to friction Reynolds number Reτ ≈ 10000 and find that with increasing Reτ, Cµ approaches a value of 0.06, which is 50% lower than the prevalent value of 0.09. Finally, we perform an a-priori test with the new (proposed) value of Cµ = 0.06 to show that the estimated turbulent viscosity νT for wall-bounded flows is in much closer agreement with the exact (DNS) values than when νT is estimated using Cµ = 0.09. The final study develops a new scaling law for wall-bounded turbulent flows. This formulation eliminates all arbitrary constants and depends only on physical parameters, namely, the free-stream velocity Um, the friction velocity U∗, the kinematic viscosity ν, and the distance from the wall z. This is a significant step towards describing the velocity profile using these pertinent parameters.
Open Access
Assessing irrigation canal seepage reduction using polymer sealants
(Colorado State University. Libraries, 2024) Lund, Ahmad Abdur Rehman, author; Scalia, Joseph, IV, advisor; Gates, Timothy K., advisor; Venayagamoorthy, S. Karan, committee member; Andales, Allan A., committee member
Irrigation canals around the world experience varying degrees of seepage losses, with several potential adverse consequences and influenced by numerous factors. A synthesis and interpretation of field seepage data from peer-reviewed literature (impact factor >1.5) on seepage measurement and control reveals several key insights: (i) seepage rates differ significantly due to diverse field conditions; (ii) the inflow-outflow method is the most reliable for measuring canal seepage in the field; and (iii) polymer sealants (PSs) offer a cost-effective alternative for reducing seepage in irrigation canals. Compared to conventional liners (CLs) such as concrete, geomembranes, or masonry, PSs are not only more affordable but also can be applied selectively, allowing for seepage when the surface water supply is sufficient and groundwater recharge is desirable. Studies show PSs can reduce seepage by 64% to 88%, while CLs achieve reductions of 53% to 95%, highlighting the potential of PSs for further research and application. However, best field application techniques for PSs, the uncertainty in evaluating effectiveness, and ambiguity in potential environmental impacts require more comprehensive investigation. The most widely researched PS for reducing canal seepage is linear anionic polyacrylamide (LAPAM), a synthetic polymer sealant (SPS). When applied to canal water, LAPAM forms flocs through cation bridging with divalent cations (Mg2+ and Ca2+) commonly found in canal water, which settle along the canal perimeter and reduce hydraulic conductivity. Observed seepage reduction from field trials of LAPAM that had been conducted prior to this study on three mid-sized canals (two in Colorado, USA and one in Sindh, Pakistan) using the recommended inflow-outflow method for seepage testing were analyzed. The average pre-LAPAM seepage rate was approximately 0.32 m/day, while the post-LAPAM rate dropped to 0.04 m/day, with results demonstrating seepage reductions between 69% and 100%. An uncertainty analysis of the pre- and post-LAPAM tests indicated an 85% probability that the seepage reductions were due to the LAPAM treatment. While LAPAM has proven effective, the long-term environmental impact of LAPAM treatment remains uncertain, underscoring the need to explore natural alternatives to synthetic polymer sealants. Biopolymer sealants (BPSs) were identified and evaluated through both laboratory and field experiments, designed to mirror the approach used with LAPAM. These experiments were conducted in triplicate (lab) and duplicate (field) to enhance confidence. In the lab, constant head saturated hydraulic conductivity (KSAT) tests simulated irrigation canal perimeter conditions. Five BPSs—pectin citrus (PC), cellulose hydroxyethyl ether (CHE), pullulan desalinated (PD), sodium alginate low viscosity (SALV), and xanthan gum (XG)—were initially tested and compared against LAPAM. The pre-and post-polymer KSAT values revealed that PC, PD, and XG achieved average reductions exceeding 40%, which was used as the threshold for further exploration. Subsequent testing under conditions more representative of irrigation canals identified XG as the most effective BPS. Alternative application rates were assessed, with 20 mg/L identified as the preferred concentration, as higher concentrations did not significantly enhance KSAT reduction. Long-term performance tests in the lab showed that XG, at 40 mg/L, can reduce hydraulic conductivity by over 90% for 9–10 months and by 60–70% over 1.5 months at 20 mg/L. These findings were validated using seepage tests in the field, where XG applied to a 3-km earthen canal reach at 20 mg/L reduced seepage by up to 63% over a month (at which time the canal was taken out of service). While the use of SPSs may still be justified for controlling canal seepage, this research shows that BPSs such as XG, have the potential to replace SPSs for canal sealing. However, further work is needed to optimize application methods and dosage rates, to better understand working mechanisms, to demonstrate long-term effectiveness, and to assess scalability across diverse field conditions.
Open Access
Simulation of successive events for multi-hazard community resilience analysis
(Colorado State University. Libraries, 2024) Harati, Mojtaba, author; van de Lindt, John W., advisor; Shields, Martin, committee member; Heyliger, Paul, committee member; Jia, Gaofeng, committee member
This dissertation, entitled "Simulation of Successive Events for Multi-hazard Community Resilience Analysis," aims to present an integrated framework for enhancing community resilience against natural hazards, with a specific focus on earthquakes and their associated impacts, such as aftershocks and tsunamis. These natural hazards pose significant threats to both coastal and non-coastal communities, leading to loss of life, injuries, and substantial socio-economic damage. A key approach to mitigating these risks is through community resilience analysis, which involves modeling the vulnerability of community infrastructure to combined source earthquake and its subsequent risks—aftershocks or tsunamis in coastal zones. In contrast to using separate fragility curves, this study develops combined earthquake-tsunami and mainshock-aftershock fragility models for a basic portfolio of reinforced concrete (RC) and woodframe structures. Governing parameters for 2D and 3D fragility functions tailored to these prototype buildings are presented, providing accessible tools for informed decision-making and mitigation strategies in community-level studies. The primary objectives are to model infrastructure vulnerability to successive seismic events and provide insights for resilience-informed decision-making. By identifying key vulnerabilities and assessing risk-based damage, dislocation, and functional recovery, the research significantly contributes to multi-hazard engineering. The proposed methodology and fragility models aim to enhance resilience-informed decision-making, allowing for strategies to improve community resilience.
Embargo
Investigating the impact of irrigation and water storage practices on hydrologic fluxes under climate change in a highly managed river basin
(Colorado State University. Libraries, 2024) Almahawis, Mohammed K., author; Bailey, Ryan T., advisor; Grigg, Neil S., committee member; Scalia, Joseph, IV, committee member; Sanford, William E., committee member
Irrigation practices and sources can have significant impacts on water resources and the hydrologic fluxes that control these resources. To better manage water resources and future water supply, the influence of irrigation practices and management on these hydrologic fluxes should be quantified in time and space at varying scales, under potential irrigation management practices. To fulfill this objective, a surface-subsurface modeling approach was applied to simulate watershed-scale hydrologic processes in the Cache la Poudre River Basin, Colorado, USA (4,824 km2), in which both surface water irrigation and groundwater irrigation are prevalent. The model chosen for this study is the watershed model SWAT+, using the spatially distributed, physically based groundwater module gwflow, in which unconfined groundwater storage, flows, and interaction with land surface features are simulated using a collection of grid cells that represent control volumes of the aquifer. Major groundwater inflows and outflows include pumping, recharge, groundwater-channel exchange, groundwater-lake exchange, and tile drainage outflow. To investigate the impact of irrigation practices, detailed surface and groundwater irrigation routines and canal-aquifer interactions were added to the SWAT+ source code, requiring information of irrigation sources and irrigation canal locations throughout the river basin. Model calibration and testing was performed using monthly stream discharge and groundwater head. The calibrated model is used to quantify the impact of surface water and groundwater irrigation scenarios on water availability and hydrologic fluxes within the river basin. A total of 22 scenarios were conducted and grouped into five main groups: irrigation source, irrigation amount, irrigation type, canal bed thickness, and partial or full sealing of earthen irrigation canals. Using groundwater as the only irrigation source decreases groundwater discharge to streams (by 14%) due to lowering groundwater levels; converting flood irrigation to sprinkler irrigation throughout the basin decreases surface runoff by 22%; and sealing earthen canals leads to a lowering of groundwater levels, which decreases groundwater discharge to streams by 9%, leading to an overall decrease in streamflow in the Cache la Poudre River and changes to temporal patterns in streamflow. Overall, irrigation amount and type and canal sealing have a small impact on total groundwater storage, compared to changes in the percent of fields irrigated by groundwater pumping. The potential impacts of climate change on water resources and hydrologic fluxes were analyzed in this study. The calibrated SWAT+gwflow model is run under five different CMIP5 climate models downscaled by MACA, each representing two different climate emission scenarios, RCP4.5 and RCP8.5. Except for the CGCM3 (Warm) model, all climate models and emission scenarios predict an increase in the yearly average temperature. The projected variation in precipitation (that is, snow and rain) depends on the climate model used. However, the average annual precipitation across the entire basin is expected to increase by 6.1% under the RCP8.5 scenario for the NorESM1-M (Mild) model. On the other hand, the IPSL-CM5A-MR (Dry) model shows a maximum decrease rate of 6% from the average climate conditions under the RCP8.5 scenario. The analysis reveals that the IPSL-CM5A-MR-8.5 climate model in the CLP is the most severe, as it combines two climatic stressors: less precipitation and increased temperature. Runoff is observed to be reduced by 47.6%, groundwater recharge to drop by 11%, and a 0.5% reduction in groundwater storage under this climate scenario. Although the climate conditions in the past have been inconsistent, the transboundary water source that flows into the watershed has consistently maintained a stable discharge throughout the investigated historical period. This indicates the existence of regulated water management methods and agreements, irrespective of the impact of climate change. The potential effects of constructing a new reservoir were also assessed in this study, specifically focusing on the influence on streamflow and hydrologic fluxes under changing climatic conditions. The calibrated SWAT+gwflow model was run using two different CMIP5 climate models downscaled by MACA, CNRM-CM5 (Wet) and IPSL-CM5A-MR (Dry) under RCP8.5 emission scenario. The analysis revealed that the CNRM-CM5 (Wet) climate scenario had a higher average monthly diversion rate from the CLP river to the Glade Reservoir during operation months (2.1 m3/s) compared to the IPSL-CM5A-MR (Dry) scenario (1.6 m3/s). Both climate models show a consistent reduction in the average annual streamflow of the CLP river when the reservoir is present. The largest reduction in the average monthly streamflow in CLP river was observed under the IPSL-CM5A-MR (Dry) RCP8.5 with reservoir scenario for the month of June, showing a 78% decrease from the historical average streamflow. The reduction in streamflow, under the reservoir scenario, for both future climate models led to a 13% and 24% reduction in surface water irrigation for the wet and dry climate scenarios, respectively, compared to historical values. Results are helpful for informed decision-making in agriculture water management and can lead to sustainable, efficient, and equitable use of water resources, helping to address the challenges posed by water scarcity and environmental conservation.
Open Access
Investigation of mineral bentonite barriers optimized for hydraulic compatibility and shear strength
(Colorado State University. Libraries, 2024) Jacob, Samuel Robert, author; Scalia, Joseph, IV, advisor; Bareither, Christopher, committee member; Sanford, William, committee member
Liners are a foundation tool of environmental geotechnics. Modern liners are constructed using natural and polymeric materials with low hydraulic conductivity (k), often at the expense of having low shear strength. These liners are often subject to high stresses on the order of hundreds to thousands of kPa which can lead to decreased performance over time and failure of the liner in shear. This research investigates mineral-bentonite mixtures in the context of high-stress liner applications. Mixtures containing varying amounts of sand, bentonite, and rock flour were created in the laboratory. Hydraulic conductivity of specimens was measured using flexible wall permeameters in accordance with ASTM D7100 using either de-ionized (DI) water, 10 mM, or 500 mM CaCl2 solutions. Specimens were removed from permeameters once k termination criteria were met and subsequently tested in direct shear at either 35 kPa or 825 kPa effective stress to obtain peak (φ´peak) and ultimate (φ´u) friction angles. Mixtures generally achieved a final k of 10- 9 m/s with bentonite contents of 4.5% and 8% when permeated with DI water and 10 mM CaCl2 solutions, respectively. Adding rock flour to mixtures containing bentonite lowered final equilibrium k but rock flour was not suitable as a complete replacement for bentonite. At 35 kPa effective stress, shear strength increased until approximately 15% equivalent fines, whereas shear strength was relatively constant at 825 kPa with increasing equivalent fines from 0-15%. At 825 kPa, shear strength substantially dropped at equivalent fines greater than 15%, which is the approximate percentage of fines that the sand matrix began to lose grain-grain contact due to the displacement by fines. The results from this study highlight that while low k and high φ´ can be achieved, even at high effective stresses, care and precision during design and construction of a mineral-bentonite barrier is required to ensure that all design criteria are met.