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  • ItemOpen Access
    Enhancing natural treatment systems by utilizing water treatment residuals
    (Colorado State University. Libraries, 2008) Yarkin, Mustafa, author; Carlson, Kenneth H., advisor
    The current project envisions the application of riverbank filtration (RBF) and aquifer recharge and recovery (ARR) in series as preliminary treatment steps of a multi-barrier treatment approach for the City of Aurora's Prairie Waters Project. The primary focus of the project is the removal of phosphorus, nitrogen, and carbon from the source water resulting in biologically stable water that can be stored in a terminal reservoir. In addition to nutrients, perchlorate and three commonly used pesticides, atrazine, alachlor, and metolachlor have been studied in terms of removal with the RBF and ARR systems. Aluminum based water treatment residual (WTR) was considered along with other sorbents for enhanced phosphorus removal. The experimental studies include the monitoring of an RBF field site and pilot columns that simulate RBF and ARR systems. Possible benefits of WTR as an amendment were tested by amending a column with 30% WTR under RBF and ARR conditions. Also an application scenario of RBF followed by a WTR amended ARR infiltration basin and ARR was simulated by a column study. Results of the studies indicated that the RBF and ARR systems are insufficient to provide sustainable phosphorus removal. Phosphorus removal mechanism is limited by the sorption capacity of the alluvial sand and minor biological activity. Use of the WTR amendment reduced phosphorus levels to less than the method detection limit of 0.03 mg/L with a high adsorption capacity. The ARR system in sequential RBF-ARR application suffers from the lack of labile organic carbon and therefore microbially mediated treatment processes are limited. Amending the infiltration of the ARR system with organic carbon rich WTR can promote biological activity, thus allowing further biodegradation of contaminants. Results of the study indicated that the RBF system is a sustainable barrier for nitrate removal while labile carbon limited ARR cannot achieve significant nitrate removal. To use the ARR system as a secondary barrier for nitrate, a labile carbon source should be introduced to the system. WTR was used as a supply of organic carbon to the ARR system and the experimental studies indicated that, once optimized, WTR can promote biological denitrification through the ARR system. The field and column studies also showed that both RBF and ARR can achieve perchlorate removal as long as sufficient electron donating compounds (e.g. organic carbon) are present in the environment. It has also been observed that the ability of RBF and ARR systems to remove alachlor and metolachlor is limited by the biodegradation through the alluvial sand while they achieve sustainable atrazine removal. WTR was tested as an amendment alternative the ARR infiltration basin. Concentrations of selected pesticides were reduced to the method detection limit of 0.3 μg/L during 1-foot 30% WTR amended column treatment with the residence time of 1.25 days under both abiotic and biotic conditions. The overall study suggested that once the source and type of the WTR was selected, the optimum amount of WTR can be obtained by adjusting the application ratio and the media depth for the efficient removal of all contaminants of concern.
  • ItemOpen Access
    Characterization of the scale dependence and scale invariance of the spatial organization of snow depth fields, and the corresponding topographic, meteorologic, and canopy controls
    (Colorado State University. Libraries, 2009) Trujillo-Gómez, Ernesto, author; Ramírez, Jorge A., advisor
    The spatial organization of snow cover properties and its dependence on scale are determined by precipitation patterns and the interaction of the snow pack with topography, winds, vegetation and radiative fluxes, among others factors. The objectives of this research are to characterize the spatial scaling properties and spatial organization of snow depth fields in several environments at scales between 1 m and 1000 m, and to determine how these properties are related to topography, vegetation, and winds. These objectives are accomplished through (a) the analysis of LIDAR elevation contours, and snow depth contours, (b) the analysis of synthetically generated profiles and fields of snow depth, and (c) simulations performed using a new cellular automata model for redistribution of snow by wind. The analyses of the power spectral densities of snow depth show the existence of two distinct scaling regimes separated by a scale break located at scales of the order of meters to tens of meters depending on the environment. The breaks separate a highly variable larger-scales interval from a highly correlated smaller-scales interval. Complementary analyses support the conclusion that the scaling behavior of snow depth is controlled by the scaling characteristics of the spatial distribution of vegetation height when snow redistribution by wind is minimal and canopy interception is dominant, and by the interaction of winds with features such as surface concavities and vegetation when snow redistribution by wind is dominant. Using these observations together with synthetic snow depth profiles and fields, we show that the scale at which the break occurs increases with the separation distance between snow depth maxima. Finally, the cellular automata model developed here is used to show that the correlation structure of the snow depth fields becomes stronger as the amount of snow transported increases, while the probability distributions of the fields progress from a Gaussian distribution for small transport rates to positively skewed probabilities for high transport rates. These simulation results are used to illustrate the controls that topography, vegetation, and winds have on the spatial organization of snow depth in wind-dominanted environments. Implications of the results from the different analysis are discussed.
  • ItemOpen Access
    Three-dimensional finite element modeling of time-dependent behavior of wood-concrete composite beams
    (Colorado State University. Libraries, 2009) To, Lam Giang, author; Gutkowski, Richard M., advisor
    The wood-concrete composite beam structure with notched shear keys has some advantages such as high composite efficiency and ease of construction with low labor cost compared to other wood-concrete composite beam structures. Made up from two rheological materials, wood and concrete, the time-dependent behavior of the wood-concrete composite beam is not only affected by the long-term load but also driven by the variation of the environmental conditions such as temperature and relative humidity. To consider the effects of the environmental conditions, the modeling process must include the moisture diffusion analysis for the wood layer, the heat transfer analysis and the stress/displacement analysis where the first two analyses provide input parameters for the third analysis. This research focused on modeling the time-dependent behavior of the layered wood-concrete composite with notched shear keys by using 3D finite element method. The main goals of the research are to expand available constitutive models of wood and concrete so that they can be used in the 3D FEM. The 3D constitutive models of wood and concrete were then implemented in the commercial software ABAQUS by using the subroutine UMAT for the stress/displacement analysis. To provide data to validate the theoretical model, a long-term creep test on two specimens has been performed. The results of the verification analysis on one test specimen captured closely the time-dependent behavior of the test specimen for the first 123 days of the test. The verification analysis revealed that the heat transfer analysis is not necessary in long-term analysis. The application of the 3D model with solid elements not only predicts the long-term behavior of the wood-concrete composite beam structures better than ID models do, but it can be also applied for wood-concrete composite structures with complex geometry where the 1D model cannot be applied. In addition, the application of the 3D model with solid element can be used to perform parametric studies to address remaining questions about time-dependent of the wood-concrete composites structures.
  • ItemOpen Access
    A spatial decision support system for basin scale assessment of improved management of water quantity and quality in stream-aquifer systems
    (Colorado State University. Libraries, 2008) Triana, Enrique, author; Labadie, John W., advisor; Gates, Timothy K., advisor
    Challenges in river basin management have intensified over the years, with expanding competition among water demands and emerging environmental concerns, increasing the complexity of the decision making framework. A State-of-the-art spatial-decision support system (River GeoDSS) is developed herein to provide assistance in evaluating management alternatives towards optimal utilization of water resources, providing a comprehensive treatment of water quantity and quality objectives based on conjunctive surface and groundwater modeling within the complex administrative and legal framework of river basin management. The River GeoDSS provides sophisticated tools that allow accurate system simulations and evaluation of strategies while minimizing the technological burden on the user. A unique characteristic of the River GeoDSS is the integration of models, tools, user interfaces and modules, all seamlessly incorporated in a geographic information system (GIS) environment that encourages the user to focus on interpreting and understanding system behavior to better design remediation strategies and solutions. The River GeoDSS incorporates Geo-MODSIM, a fully functional implementation of MODSIM within the ArcMap interface (ESRI, Inc.), and Geo-MODFLOW, a new MODFLOW-MT3DMS results analysis tool in the ArcMap interface. The modeling system is complemented with a new artificial neural networks (ANN) module for natural and irrigation return flow quantity and quality evaluation and salt transport through reservoirs, as well as with a new water quality module (WQM) for conservative salt transport modeling of conjunctive use of surface water and groundwater resources in the river basin network. In this research, innovative methodologies are developed for applying ANNs in efficiently coupling surface and groundwater models for basin-scale modeling of stream-aquifer interactions. The core River GeoDSS is customized to provide comprehensive analysis of alternative solutions to achieving agricultural, environmental, and water savings goals in the Lower Arkansas River Basin in Colorado while assuring physical, legal and administrative compliance. The River GeoDSS applied to the Arkansas River Valley allowed comparing benefits and improvements of management strategies, illustrated their potential to reduce waterlogging and soil salinity, salt load to the river, and non-beneficial evapotranspiration in a strategic planning environment.
  • ItemOpen Access
    Effects of principal stress rotation and intermediate principal stress changes on the drained monotonic and undrained cyclic behavior of clean and nonplastic silty Ottawa sands formed underwater
    (Colorado State University. Libraries, 2009) Tastan, Erdem Onur, author; Carraro, Antonio, advisor
    A state-of-the-art dynamic hollow cylinder apparatus was used to systematically study the effect of drained changes in the major principal stress direction (a, taken from the vertical) and intermediate principal stress coefficient (b) on the (1) drained static and (2) undrained cyclic stress-strain responses, and (3) liquefaction resistance of clean and nonplastic (NP) silty Ottawa sands formed underwater. A modified slurry deposition method was developed to reconstitute HC clean and NP silty Ottawa sand specimens in a way that resembles the actual field deposition of these soils underwater. Using a new density gradient mold developed during this study, the maximum local deviations of relative density (D R) and fines content (FC) from their global averages were determined to be as small as (or lower) than the deviations obtained for similar reconstitution methods typically used for solid triaxial specimens. Drained increases in a and/or b at constant mean normal effective stress and octahedral deviator stress were shown to induce strains as large as those induced during anisotropic- K0 consolidation, with the NP silty Ottawa sand typically yielding larger strains than the clean Ottawa sand at similar states. As a increased, the sands exhibited weaker undrained cyclic responses. However, the relative effect of a on soil response appears to be less significant for Ottawa sands with NP silt content between 11% and 15%. Increase in b improved the liquefaction resistance of the sands. However, when both a and b were greater than zero, their combined effect typically decreased the liquefaction resistance of the sand, suggesting that a may play a more dominant role on the undrained response of the sand than b. Undrained instability was observed in many tests carried out on anisotropically consolidated specimens subjected or not to a and/or b changes. Occurrence of undrained instability depends upon the cyclic stress ratio, a, b, DR and FC of the soil. The results of this study indicate that liquefaction analyses based on axisymmetric parameters may be unconservative for most types of geotechnical applications since axisymmetric conditions do not account for the effect of a on the liquefaction resistance of the soil. Appropriate evaluation of the liquefaction potential of a soil requires consideration of both a and b, although the major controlling mechanism might be associated with the mechanical response imparted by drained principal stress rotation. The results obtained in this study may be used to develop new or improve and calibrate current constitutive models that address soil anisotropy and more realistic loading conditions in geotechnical analyses. Typical applications of such advanced models include geotechnical analyses of slope stability, design of foundations, dams, embankments, pavement subgrades, and retaining structures, particularly those involving tailings, hydraulic fills, and alluvial or marine deposits of sands with fines formed underwater.
  • ItemOpen Access
    Source-tracking of antibiotic resistance genes in the watershed using molecular profiling and geospatial analyses
    (Colorado State University. Libraries, 2009) Storteboom, Heather, author; Arabi, Mazdak, advisor
    Antibiotic resistance genes (ARG) have been found in many environmental matrices, including soils, groundwater, surface water, and sediments. Agricultural feeding operations and wastewater treatment plants are potential sources of ARG in rivers, or are sources of antibiotics that may select ARG from native river bacteria. The aim of this research is to identify ARG profiles that can characterize potential sources of ARG as well as native river environments and then use this knowledge to determine the sources and mechanisms involved in the spread of ARG to river environments. Initially, three wastewater treatment plants, six animal feeding operation lagoons, three sites along a pristine region of the Cache la Poudre River (PR), and a wildlife fish hatchery and rearing unit were compared with respect to the distribution, levels, and phylogenetic diversity of their ARG profiles. The tet genes tet(H), tet(Q), tet(S), and tet(T) were found to indicate agricultural influence, while high detection frequencies of tet(C), tet(E), and tet(O) were more typical of WWTP profiles. Sul(I) was detected in 100% of samples from source environments, but just once in the pristine river environment. The ARG profile of the pristine PR was dominated by tet(M) and tet(W), demonstrating their presence in an environment does not indicate anthropogenic disturbance. The tet(W) clone libraries from Pristine PR, WWTPs, and AFO lagoons, are each unique, as determined by both restriction fragment length polymorphism (RFLP) and phylogenetic analysis. Secondly, samples from the PR and South Platte River (SPR) in Northern Colorado were characterized with respect to the distribution, levels, and diversity of their ARG profiles. On the basis of the ARG indicator variables derived in the study of source environments, most river samples were classified as WWTP influenced by discriminant analysis. The relationship between spatial explanatory variables and the ARG response variables was determined with classification and regression tree (CART) analysis. There was good agreement between the classification of river sites according to spatial variables and source indicator variables, demonstrating the effectiveness of these indicators in source-tracking ARG. According to multivariate linear regression, sul(I) was significantly correlated with the inverse-distance weighted (IDW) number of cattle upstream of each river point (R2 = 0.83, p <0.0003), whereas tet(W) was not correlated with any explanatory variable tested. Tet(W) was isolated from two river environments: site PR4, located in Weld County downstream of Fort Collins; and site SPR3, located downstream of the confluence of the PR with the SPR. When compared to an existing clone library of tet(W) genes from animal feeding operations and wastewater treatment plants, PR4 was significantly different from the animal feeding operations (p<0.05); the SPR confluence (SPR3) was not significantly different from either environment. The PR4 environment was most similar to that of wastewater treatment plants, while SPR3 showed equal similarity with both source environments. A link between ARG indicator variables and spatial indicators was established. Furthermore, it was demonstrated that the ARG profiles of river samples were more similar to WWTPs than AFO lagoons or the pristine river. Based on this work, transport of ARG from sources may be a reasonable mechanism for ARG proliferation in riverine environments.
  • ItemOpen Access
    Remediation of arsenic and persistent organic contaminants using enhanced in-situ methods
    (Colorado State University. Libraries, 2008) Sullivan, Mary Elizabeth, author; Carlson, Kenneth, advisor; Pruden, Amy, advisor
    The demand for inexpensive and reliable water treatment technologies continues to increase as the number of contaminants grows and their associated fate and transport mechanisms become more complex. Advances in public health have contributed to the implementation of more stringent drinking water standards for compounds such as arsenic. Furthermore, advances in analytical chemistry have contributed to the detection of previously immeasurable compounds including endocrine-disrupting compounds (EDCs), pharmaceuticals and personal care products (PPCPs), and other bioactive chemicals in wastewater effluents and surface waters around the world. This research examined the use of enhanced in-situ methods for the remediation of arsenic and several persistent organic contaminants. Unamended and amended electrokinetic remediation (ER) column studies conducted to determine the impact on arsenic revealed arsenic removal from the soil column due to the electrolysis of water and electromigration of the charged species. Column studies also examined the impact of amended aquifer recharge and recovery (ARR) treatment on persistent organic compounds. Water treatment residual-amended ARR columns were utilized to promote an environment capable of reducing flame retardants. The results indicated that the presence of water treatment residuals created a reducing environment and provided ideal adsorption sites and sources of organic matter in the form of leached carbon. Unamended and amended ER column studies were completed to examine the impact on two pharmaceuticals (sulfamethoxazole and carbamazepine) and three organophosphorus flame retardants (tris-(2-chloroethyl) phosphate, tris-(2-chloro-, 1-methylethyl)phosphate, and tris-(2-chloro-, 1-chloromethyl-ethylphophate). Results indicated that the highest removal results occurred in the significant redox zones of the ER column. Oxidizing conditions at the anode and reducing conditions at the cathode had significant impacts on the compounds' concentrations in the column's pore water. Lastly, critical characterization of the compounds' affinity for aqueous, colloidal, and solid phases was determined for the five organic compounds. These results, as well as sources of flame retardant contamination in the experimental design, was useful (and necessary) in interpreting the treatment results from the amended ARR and electrokinetic column studies.
  • ItemOpen Access
    Series expansion of the Modified Einstein Procedure
    (Colorado State University. Libraries, 2009) Shah-Fairbank, Seema Chandrakant, author; Julien, Pierre Y., advisor
    This study examines calculating total sediment discharge based on the Modified Einstein Procedure (MEP). A new procedure based on the Series Expansion of the Modified Einstein Procedure (SEMEP) has been developed. This procedure contains four main modifications to MEP. First, SEMEP solves the Einstein integrals quickly and accurately based on a series expansion. Next, instead of dividing the suspended sediment and bed material samples into particle size classes, the total sediment discharge calculation is based on a median grain size in suspension (d50ss). Thirdly, for depth-integrated samples the Rouse number (Ro) is determined directly by calculating the fall velocity (ω) based on dsoss, the shear velocity (u. = -√ghS) and assuming the value of the von Karman constant (κ) is 0.4. For point concentration measurements, the Ro is calculated by fitting the concentration profile to the measured points. Lastly, SEMEP uses the measured unit sediment discharge and Ro to determine the unit bed discharge directly. Thus, SEMEP can determine the unit bed discharge (qb), unit suspended sediment discharge (qs), unit total sediment discharge (qt), ratio of measured to total sediment discharge (qm/qt) and ratio of suspended to total sediment discharge (qs/qt).
  • ItemOpen Access
    Design and implementation of hydrologic unit watersheds for rainfall-runoff modeling in urban areas
    (Colorado State University. Libraries, 2009) Rivas Acosta, Iván, author; Roesner, Larry A., advisor
    The calibration of complex hydrology and hydraulics of rainfall-runoff models represents one of the most challenging problems in water resources engineering. Unlike undeveloped watersheds, but specifically urban basins with surface drainage. From the available models, SWMM (Storm Water Management Model) was used as the modeling engine since it was developed for urban watersheds. Calibration procedure used a Multi-Criteria Decision Analysis (MCDA) approach that minimized the RMSE (Root Mean Square Error) between the flow duration curves of the modeled and the observed runoff. The flow duration curve was divided in High and Low Flows using the 1-Yr storm to split the curve, since there is a change in flow regime at this point. Pareto optimal front surfaces were obtained. Two case studies in North Carolina (Pigeon and SW Prong basins) were used to illustrate a proposed methodology for calibration. The methodology simplified the drainage network and irregular sub-catchments shapes were converted to regular shapes using a Kinematic Wave (KW) cascading plane approach. The KW cascading plane approach showed to be effective to convert irregular sub-basins shapes to rectangular features. A discretization analysis was performed where a set of hydrologic experiments using different levels of discretization were used and a threshold discretization value in urban hydrology was investigated. Needed GIS data was extracted through a toolbox. MCDA methodology and numerical simulations showed that Horton's decay coefficient (K, 1/h) and drying time (Tw, days) needed to have different values for the High and Low Flow portions of the flow duration curve to improve performance. Longer drying times were required to improve estimation of High Flows than Low Flows because the soils would take more time to recover their initial infiltration capacity. The Representative Element Area (REA) concept was explored in SWMM and it was found that sub-catchment sizes of 3% of the total basin size were appropriate. This magnitude represents the suggested level of discretization in urban watersheds since the improvement in performance became asymptotic either to 1.00 (Pearson's Moment Correlation Coefficient-PMCC, Nash-Sutcliff Coefficient-NSC and Index of Agreement-IOA) or to zero (RMSE) and therefore, it is not significant to improve the spatial resolution. Coarser resolution levels underestimated peak flow rates and total runoff volumes. Research results are summarized in a proposed protocol to discretisize urban watersheds.
  • ItemOpen Access
    High-volume use of self-cementing spray dry absorber material for structural applications
    (Colorado State University. Libraries, 2009) Riley, Charles E., author; Heyliger, Paul R., advisor; Atadero, Rebecca A., advisor
    Spray dry absorber (SDA) material, or spray dryer ash, is a byproduct of energy generation by coal combustion and sulfur emissions controls. Like any resource, it ought to be used to its fullest potential offsetting as many of the negative environmental impacts of coal combustion as possible throughout its lifecycle. Its cementitious and pozzolanic properties suggest it be used to augment or replace another energy and emissions intensive product: Portland cement. There is excellent potential for spray dryer ash to be used beneficially in structural applications, which will offset CO2 emissions due to Portland cement production, divert landfill waste by further utilizing a plentiful coal combustion by-product, and create more durable and sustainable structures. The research into beneficial use applications for SDA material is relatively undeveloped and the material is highly underutilized. This dissertation explored a specific self-cementing spray dryer ash for use as a binder in structural materials. Strength and stiffness properties of hydrated spray dryer ash mortars were improved by chemical activation with Portland cement and reinforcement with polymer fibers from automobile tire recycling. Portland cement at additions of five percent of the cementitious material was found to function effectively as an activating agent for spray dryer ash and had a significant impact on the hardened properties. The recycled polymer fibers improved the ductility and toughness of the material in all cases and increased the compressive strength of weak matrix materials like the pure hydrated ash. The resulting hardened materials exhibited useful properties that were sufficient to suggest that they be used in structural applications such as concrete, masonry block, or as a hydraulic cement binder. While the long-term performance characteristics remain to be investigated, from an embodied-energy and carbon emissions standpoint the material investigated here is far superior to Portland cement.
  • ItemOpen Access
    Performance modeling of stormwater best management practices with uncertainty analysis
    (Colorado State University. Libraries, 2009) Park, Daeryong, author; Roesner, Larry A., advisor; Loftis, Jim C., advisor
    Best management practices (BMPs) contain many uncertainties that make it difficult to determine their performance with a model. Moreover, predicting BMP performance with existing methods is not easy. The major research objective of this dissertation is to incorporate uncertainty analysis in a BMP performance model to better represent its treatment performance. The k-C* model is used in this study to simulate BMP performance, and the study assumes that the influent event mean concentration (Cin) and aerial removal constant (k) include uncertainty. Both Cin and k represent data and model uncertainty. To evaluate the model, three different uncertainty cases, uncertainty in Cin, k, and both Cin and k, are applied to the total suspended solid (TSS) data of detention basins and retention ponds. To evaluate uncertainty values, three different uncertainty analysis methods, the derived distribution method (DDM), the first-order second-moment method (FOSM), and the latin hypercube sampling (LHS), are applied to each case. TSS, as a representative pollutant, and detention basins and retention ponds, as representative BMPs, are utilized in this study. The observed datasets are selected from the International Stormwater BMP database. By incorporating uncertainty analysis into the k-C* model, the effect of BMP surface area and inflow on the effluent event mean concentration (Cout) of TSS can be quantified for detention basins and retention ponds. These effects are not large in detention basins but are noticeable in retention ponds. In addition, the k-C* model with uncertainty analysis is applied to a hypothetical watershed to show how uncertainty might be used improve the probability of compliance with TMDLs.
  • ItemOpen Access
    Development and application of functional gene profiling and quantification of microbial communities remediating mine drainage
    (Colorado State University. Libraries, 2009) Pereyra, Luciana Paula, author; Pruden, Amy, advisor; Reardon, Kenneth F., advisor
    Mine drainage (MD) is the product of the oxidation of sulfide minerals. It is characterized by elevated concentrations of heavy metals and sulfate and acidic to near-neutral pH. Sulfate-reducing permeable reactive zones (SR-PRZs) represent a common passive treatment approach for MD. Although SR-PRZs are microbially catalyzed, little is known about their microbiology and ecology. In this research, several aspects of the SR-PRZ microbial community were explored at laboratory and pilot scales with established as well as newly developed biomolecular methods. A study using microcosm column experiments demonstrated that the type of inoculum plays an important role in the bioremediation of MD. The effect of the type of substrate on the microbial community was also investigated in pilot-scale SR-PRZs treating the MD. Lignocellulose-based SR-PRZs contained a more diverse microbial community and higher bacterial density than ethanol-fed SR-PRZs, as determined by 16S rRNA gene cloning and quantitative polymerase chain reaction (Q-PCR). A new biomolecular approach was developed to target genetic markers of the functions of interest (functional genes): cellulose degradation, fermentation, sulfate reduction, and methanogenesis. This approach provided a more efficient and direct means of studying microbial functions. The functional gene-based approach was adapted to denaturing gradient gel electrophoresis and Q-PCR and applied to study the microbial communities in laboratory columns simulating SR-PRZs during the initial and pseudo-steady-state operation. Although the microbial communities in the different treatments were different during pseudo-steady-state operation, performance of the columns was comparable in terms of sulfate and metal removal and pH neutralization. This suggests that various microbial compositions can lead to successful MD remediation. The studies presented in this dissertation provide significant insight in the microbial communities involved in MD remediation at laboratory and pilot scale. In addition, a variety of biomolecular methods are presented that can be applied to explore different aspects of the microbial community not only in SR-PRZs and but also in other systems with complex microbial communities. Integration of biomolecular and performance data will provide a more complete understanding of SR-PRZ function that could be used to improve SR-PRZ performance and reliability.
  • ItemOpen Access
    Characterizing hydroclimatic variability in tributaries of the Upper Colorado River Basin - WY 1911-2001
    (Colorado State University. Libraries, 2009) Matter, Margaret A., author; Garcia, Luis A., advisor; Fontane, Darrell G., advisor
    Mountain snowpack is the main source of water in the semi-arid Colorado River Basin (CRB), and while the demands for water are increasing, competing and often conflicting, the supply is limited and has become increasingly variable over the 20th Century. Greater variability is believed to contribute to lower accuracy in water supply forecasts, plus greater variability violates the assumption of stationarity, a fundamental assumption of many methods used by water resources engineers in planning, design and management. Thus, it is essential to understand the underpinnings of hydroclimatic variability in order to effectively meet future water supply challenges. A new methodology was applied to characterize time series of temperature, precipitation, and streamflow (i.e., historic and reconstructed undepleted flows) according to the three climate regimes that occurred in CRB during the 20th Century. Results for two tributaries in the Upper CRB show that hydroclimatic variability is more deterministic than previously thought because it entails complementary temperature and precipitation patterns associated with wetter or drier conditions on climate regime and annual scales. Complementary temperature (T) and precipitation (P) patterns characterize climate regime type (e.g., cool/wet and warm/dry), and temperatures increase or decrease and precipitation changes magnitude and timing according to the type of climate regime Accompanying each climate regime type, are complementary T and P patterns on annual scales that are associated with upcoming precipitation and annual basin yield. Annual complementary T and P patterns: (a) establish by fall; (b) are detectable as early as September; (c) persist to early spring; (d) are related to the relative magnitude of upcoming precipitation and annual basin yield; (e) are unique to climate regime type; and (f) are specific to each river basin. Thus, while most of the water supply in the Upper CRB originates from winter snowpack, statistically significant indictors of relative magnitude of upcoming precipitation and snowmelt runoff are evident in the fall, well before appreciable snow accumulation. Since natural and anthropogenic external forcings, including solar variability, anthropogenic climate change, and modifications to land use, land cover and water use, influence the climate modes that shape climate regimes, the external forcings also influence the complementary temperature and precipitation patterns accompanying each climate regime. Consequently, although complementary temperature and precipitation patterns are similar for climate regimes of the same type (e.g., cool/wet climate regimes), they also differ and the differences may be associated with anticipated or observed effects of external forcings. In summary, this research shows that hydroclimatic variability during the 20th Century is more deterministic than previously thought, and includes: (a) a series of alternating patterns in temperature and precipitation corresponding with changes in climate regimes; and (b) effects of anthropogenic external forcings on the complementary temperature and precipitation patterns accompanying the climate regimes. Results of this research suggest alternative strategies to incorporate into existing water supply forecasting methods to improve forecast accuracy and increase lead time up to six months, from April 1 to October 1 of the previous year. Based on the relationships revealed by this research, the physical mechanisms behind the relationships may be determined and used to improve models for water supply forecasting and water management; develop long-range forecasts; and downscale climate models. In addition, the research results may also be used: (a) to improve application of or develop alternatives to engineering and hydrologic methods based on the assumption of stationarity; (b) in developing science-based adaptive management strategies for natural and cultural resource managers; and (c) in developing restoration, conservation and management plants for fish, wildlife, forest, and other natural resources.
  • ItemOpen Access
    Structural coupling and wind-induced response of twin tall buildings with a skybridge
    (Colorado State University. Libraries, 2008) Lim, Juntack, author; Bienkiewicz, Bogusz, advisor
    Twin tall buildings with a connecting skybridge involve two types of coupling: the structural coupling, developed by a skybridge and synchronizing the motions of vibration of the two building and the aerodynamic coupling resulting from high cross-correlations of the components of wind loading. The physical understanding of these couplings and their impacts on the wind-induced response of the buildings are not fully understood, when using a high-frequency force balance (HFFB) approach tailored for single tall buildings. Detailed laboratory mapping of the aerodynamic loading and coupling requires specialized experimental techniques. Predictions of the response of the structurally coupled buildings, due to correlated wind loading, involve utilization of advanced dynamic analysis. This dissertation addresses the issues associated with correlated wind loading and structurally coupled response of twin buildings with a skybridge. Wind tunnel testing to acquire the correlated wind loading on twin buildings is described. The effects of the relative positions of the buildings on the loading correlations and coherences are discussed. These results are next used as an input to an analytical model developed to calculate the building wind-induced response. The building system, including the structural coupling, is represented by a six-degree-of-freedom model lumped at the skybridge level. In free vibration, the natural frequencies and modal shapes are obtained for various levels of the relative stiffness of the (inter-building) beam representing the skybridge. The model is subsequently used to investigate the effects of aerodynamic and structural couplings on the roof top accelerations of the buildings. Spectral integration and white-noise approximation approaches are employed in calculations of the building responses. The presented results show significant effects of both the aerodynamic and structural couplings. Simplified empirical relations for application in preliminary design of structurally connected tall buildings are proposed. Recommendations for follow-up studies of coupled wind-induced response of tall twin buildings are discussed.
  • ItemOpen Access
    Methodology for evaluating flood damage reduction alternatives using a GIS-based MCDA interactive model
    (Colorado State University. Libraries, 2008) Lim, Kwang-Suop, author; Fontane, Darrell G., advisor; Grigg, Neil S., advisor
    Floodplain management involves the use of spatial physical information and information on decision makers' preferences. Both of these sources of information can have various degrees of imprecision. This research proposed a combined geographic information system (GIS) with Multi-Criteria Decision Analysis (MCDA). The use of GIS can give technical specialists and ultimately decision makers the possibility to find more spatially distributed information. These can be used to augment, an MCDA approach, which is an efficient tool for considering multiple-criteria in deciding on the best alternatives in a synthesized and integrated manner. The outcome of a floodplain management study is typically a recommendation for a single alternative flood management strategy. If this is developed by simply averaging over the entire floodplain, information is lost about the impact of the various alternatives on specific points in the floodplain. The ability to view this spatially distributed information could provide decision makers with a better understanding of the impacts of selected a specific alternative. Finally, a "cost of uniformity" metric is proposed that allows the decision makers to better determine the impact of selecting a single alternative for the floodplain by considering the spatially diverse information developed in the MCDA. The target region for a demonstration application of the methodology was the Suyoung River Basin in Korea. The 1991 Gladys flood event and five different return periods were used as a case study to demonstrate the proposed methodology of evaluation of various flood damage reduction alternatives. Through a case study, the characteristics of four different MCDA methods and the impact of inserting additional criteria into the MCDA are examined and compared. Based upon the comparison between the methods, it has been illustrated that the Improved Spatial Fuzzy Weighted Average Method using an S-shaped Membership Function applied to adjusted digital elevation maps provides enhanced information for evaluating flood damage reduction alternatives.
  • ItemOpen Access
    The effect of parameter uncertainty in stochastic streamflow simulation
    (Colorado State University. Libraries, 2009) Lee, Dong-Jin, author; Salas, Jose D., advisor
    Hydrologic time series simulation based on a stochastic model is intended to obtain a set of equally likely hydrologic sequences that could possibly occur in the future and might be useful for determining the uncertainty of decision variables such as the storage capacity of a reservoir. Since stochastic models generally hinge on parameters that are estimated based on a limited historical sample, the model parameters become uncertain and so are any decision variables that are derived from the generated samples. The main objective of this study is to propose and analyze methods for quantifying the effect of parameter uncertainty of the models that are used in the generation of synthetic streamflow series. As a way of quantifying parameter uncertainty of a stochastic model, asymptotic and Bayesian approaches have been implemented and their performances compared through extensive simulation experiments. Alternative streamflow simulation techniques have been utilized with parameter uncertainty incorporated such as stochastic models of annual streamflows at single and multiple sites as well as temporal and spatial disaggregation models. The impact of parameter uncertainty is shown to increase the variability of generated flow statistics and resultant design related variables, which is visible even with a relatively large sample size, e.g. sample size of 200. The Bayesian approach produces larger variability of generated statistics for small sample sizes than the asymptotic approach, and the difference between the two approaches is more evident for the case of generation of streamflows with high serial correlations. The effect of parameter uncertainty within disaggregation models is not as significant on the first and second moments of disaggregated flows as the effect of parameter uncertainty of the models that generate the input variables; whereas the effect of parameter uncertainty of disaggregation models results in more variability of month-to-month, month-to-annual, and cross correlations than those induced by the uncertainty of the model parameters of input variables.
  • ItemOpen Access
    Stochastic simulation of hydrologic data based on nonparametric approaches
    (Colorado State University. Libraries, 2008) Lee, Taesam, author; Salas, Jose D., advisor
    Stochastic simulation of hydrologic data has been widely developed for several decades. However, despite the several advances made in literature still a number of limitations and problems remain. The major research topic in this dissertation is to develop stochastic simulation approaches to tackle some of the existing problems such as the preservation of the long-term variability and the joint modeling of intermittent and non-intermittent stations. For this purpose, nonparametric techniques have been applied. For simulating univariate seasonal streamflows, a model is suggested based on k-nearest neighbors resampling (KNNR). Gamma kernel density estimate (KDE) perturbation is employed to generate realistic values of streamflow that are not part of the historical data. Further, aggregate and pilot variables are included in KNNR so as to reproduce the long-term variability. For multivariate streamflows, the moving block bootstrapping procedure is employed considering a random block length, KNNR block selection to avoid the discontinuity between blocks, a Genetic Algorithm mixture, and Gamma KDE perturbation. In addition, the drawbacks of an existing nonparametric disaggregation scheme have been examined and appropriate modifications developed that include accurate adjusting for the disaggregate variable, KNNR, and Genetic Algorithm mixture. The suggested univariate, multivariate, and disaggregation models have been compared with existing nonparametric models using several cases of streamflow data of the Colorado River System. In all cases, the results showed major improvements. Furthermore, disaggregation from daily to hourly rainfall for a single site has been studied based on three disaggregation models so as to account for the diurnal cycle in hourly data. Those models are (1) Conditional Markov Chain and Simulated Annealing (CMSA), (2) Product Model (GAR(1)-PDAR(1)) with Accurate Adjusting (PGAA), and (3) Stochastic Selection Method with Weighted Storm Distribution (SSMW). Various tests and comparisons have been performed to validate the models and it revealed that PGAA is superior to the others for preserving the diurnal cycle and the key statistics of hourly rainfall.
  • ItemOpen Access
    Membrane behavior of clay liner materials
    (Colorado State University. Libraries, 2008) Kang, Jong Beom, author; Shackelford, Charles D., advisor
    Membrane behavior represents the ability of porous media to restrict the migration of solutes, leading to the existence of chemico-osmosis, or the flow of liquid in response to a chemical concentration gradient. Membrane behavior is an important consideration with respect to clay soils with small pores and interactive electric diffuse double layers associated with individual particles, such as bentonite. The results of recent studies indicate the existence of membrane behavior in bentonite-based hydraulic barriers used in waste containment applications. Thus, measurement of the existence and magnitude of membrane behavior in such clay soils is becoming increasingly important. Accordingly, this research focused on evaluating the existence and magnitude of membrane behavior for three clay-based materials that typically are considered for use as liners for waste containment applications, such as landfills. The three clay-based liner materials included a commercially available geosynthetic clay liner (GCL) consisting of sodium bentonite sandwiched between two geotextiles, a compacted natural clay known locally as Nelson Farm Clay, and compacted NFC amended with 5% (dry wt.) of a sodium bentonite. The study also included the development and evaluation of a new flexible-wall cell for clay membrane testing that was used subsequently to measure the membrane behaviors of the three clay liner materials. The consolidation behavior of the GCL under isotropic states of stress also was evaluated as a preliminary step in the determination of the membrane behavior of the GCL under different effective consolidation stresses.
  • ItemOpen Access
    An urban geomorphic assessment of the Berryessa and Upper Penitencia Creek watersheds in San Jose, California
    (Colorado State University. Libraries, 2009) Jordan, Brett, author; Watson, Chester C., advisor
    A paired watershed study for two adjacent urbanized watersheds in San Jose, California was conducted to investigate vastly different channel morphologic response to urbanization and valley subsidence. The urbanized portion of Berryessa Creek (15.5 km2) exhibits system-wide channel instability, meanwhile Upper Penitencia Creek (61.3 km2) has remained stable despite similar urban build out trends. Currently, there is a paucity of field measurements documenting channel response to urbanization and subsidence in the academic literature. Detailed geomorphic field surveys were undertaken to establish 90 permanent cross sections over 9.2 km of urban channel. These surveys were used for sediment transport modeling in this study and will provide a permanent monitoring network. Historic data sources were utilized to establish a baseline context and chronicle change in the watersheds. The historic data sources, field data, and numerical modeling were used to investigate the relative effects of hydrologic alteration, valley subsidence, and river infrastructure on water yield, sediment yield, and channel stability. Drainage area capture by the urban storm sewer network, a component of urbanization that has not previously been addressed in the scientific literature, and engineered river infrastructure elements are the primary causes of system-wide channel instability in the urbanized valley portion of Berryessa Creek. Hydrologic and sediment transport modeling indicates that drainage area capture and urban land use change has increased water yield 48% and sediment yield up to 61% from 76 to 121 tonnes/yr-km2. These hydrologic changes have transformed historically depositional reaches into incised reaches leading to system wide instability. An on-line sedimentation basin and a 1.85 m grade-control structure have reduced downstream sediment yield by 15% from 88 to 76 tonnes/yr-km 2 and increased channel incision rates by capturing coarse bed material in transport. Models indicate that measured valley subsidence of 0.23 m results in upstream incision, however sediment yield is not affected and the morphologic response to subsidence is likely obscured by current instability processes dominant in the system. In the current hydrologic regime of Upper Penitencia Creek, flow diversion and basin reduction by the storm sewer network offset increased runoff produced by the urban landscape and channel stability is not adversely affected by the hydrologic alteration. Water yield is increased by 7%, however sediment yield is reduced by 4% from 41.7 to 39.8 tonnes/yr-km2 at the outlet. River infrastructure in the form of a system of small grade-control structures aids in the stability of the upstream reaches. Valley subsidence of 1.1 m is predicted to cause incision that would progress 1800 m upstream of the zone of maximum subsidence. Modeling results were verified by reach-scale instability observed upstream of the subsidence zone. The reach scale instability is a result of increase stream power resulting from valley subsidence and channel realignment.
  • ItemOpen Access
    Design of converging stepped spillways
    (Colorado State University. Libraries, 2008) Hunt, Sherry Lynn, author; Abt, Steven, advisor
    Roller compacted concrete (RCC) stepped spillways are growing in popularity for providing overtopping protection for aging watershed dams with inadequate auxiliary spillway capacity and for the construction of new dams. Unobtainable land rights, topographic features, and land use changes caused by urbanization limit the ability to construct new dams or modify the dimensions of existing embankments and spillways. The advantages of stepped spillways are (1) they can be placed over the top of an existing embankment without causing significant changes to the dam or spillway dimensions, (2) they provide considerable energy dissipation in the chute, potentially reducing the size of the stilling basin, and (3) they permit shorter, more efficient, and feasible construction schedules than other design options. Currently, limited design guidelines are available in the literature for the design of stepped spillways constructed on flat slopes (&thetas; < 30°). Auxiliary spillways are designed to safely pass exceptionally large flood events to the downstream channel. In structural auxiliary spillways, spillway chute and stilling basin training walls are typically designed to prevent overtopping. However, the aspect of converging training walls increases the flow depth in the chute near the walls, and it changes the hydraulic parameters for designing the stilling basin. To assist with the design of converging stepped spillways having similar design parameters (i.e. chute slope, step height, etc.), a study utilizing a three-dimensional, 1:22 scale physical model was conducted to evaluate the flow characteristics in the spillway. This study is the first known attempt at developing generalized design criteria for converging stepped spillways having vertical training walls. Conclusions drawn from this study are that as the convergence of the training wall increases the flow depth near the wall also increases. A simplified control volume momentum analysis was used to predict the minimum training wall height necessary to prevent overtopping. The equation developed slightly under-predicted the results. This under-prediction may be a result of the assumptions made in the development of the prediction equation. Other design aids for determining training wall height were developed based on observations with the data. The results of the study will be discussed further herein.