Browsing by Author "Butters, Greg, committee member"
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Item Open Access Effects of capping material on longevity of degradable contaminants in sediments(Colorado State University. Libraries, 2017) Campbell, Calista Emily, author; Sale, Tom, advisor; Blotevogel, Jens, committee member; Butters, Greg, committee memberTo view the abstract, please see the full text of the document.Item Open Access Effects of gully topography on space-time patterns of soil moisture in a semiarid grassland(Colorado State University. Libraries, 2009) Melliger, Joshua J., author; Niemann, Jeffrey D., advisor; Butters, Greg, committee member; Bledsoe, Brian, committee memberGullies are pervasive topographic features in semiarid grasslands in North America. At the Army’s Piñon Canyon Maneuver Site (PCMS) in southeastern Colorado, gullies are important because they restrict the mobility of troops and vehicles in training exercises, and they represent areas that are potentially vulnerable to further erosion. Substantial research has examined the temporal evolution of gullies as well as the factors that initiate gullies and control their morphology. In particular, prolonged periods of low soil moisture (droughts), frequent flash floods, and human activity are thought to reduce vegetative cover and promote gully development. Much less is understood about the feedback of gully topography on space-time patterns of soil moisture. The presence of gullies may produce feedbacks to soil moisture that either enhance or diminish gully development. In this study, field observations from PCMS are used to study the effects of gullies on space-time patterns of soil moisture and to describe the interactions of soil moisture, soil texture, and vegetation around gullies. Three study sites at PCMS have been extensively instrumented. These sites are located in the same broad valley, but one site (~1500 m2) is ungullied while the other two sites (also ~1500 m2) each contain a gully. The gully sites are adjacent to each other and their two gullies are approximately parallel. Hourly soil moisture observations have been collected for 8 months at two sites and 4 months at one site using time domain reflectometry (TDR) probes installed along four transects within each site. Each transect contains 6-8 probes that are positioned at the mid-points between topographic breakpoints. Meteorological data are also collected at the ungullied site and between the two gullied sites. Overall, the occurrence of gullies was observed to not affect the spatial average soil moisture within the study sites, but the gullies do promote spatial variability in soil moisture. Gully bottoms tend to be wetter. Although the evidence here is not conclusive, this tendency may be due to gradual lateral inflows, thicker vegetation (which protects the soil against surface crusting and promotes infiltration), and the lower local elevations (which protect against higher wind speeds and evapotranspiration). The gully sidewalls tend to be drier because of rapid drainage during and after precipitation events and in some cases increased solar insolation.Item Open Access Effects of woody vegetation on shallow soil moisture at a semiarid montane catchment(Colorado State University. Libraries, 2013) Traff, Devin, author; Niemann, Jeffrey D., advisor; Green, Timothy R., committee member; Butters, Greg, committee memberSoil moisture plays an integral role in many ecohydrologic processes and applications, particularly in semiarid environments. While interactions between vegetation and soil moisture at greater depths are relatively well understood, less is known about soil moisture at depths of 5 cm or less. In this study we investigate the impact of woody vegetation on shallow soil moisture dynamics for forested and shrubland ecosystems in a semiarid montane catchment. Instrumentation was installed on a forested north-facing hillslope (NFS) and a south-facing hillslope (SFS) vegetated primarily by shrubs at three types of locations: open or intercanopy, under mountain mahogany (Cercocarpus montanus) shrubs, and under ponderosa pine (Pinus ponderosa) trees. Rain gauges and pyranometers were installed to assess the impact of interception and shading, while time-domain reflectometry (TDR) probes were inserted into the top 5 cm of the soil to monitor hourly soil moisture. The observations suggest that interception reduces throughfall to about 25-50% of rainfall under the mountain mahogany and ponderosa pines. Shading is important for all locations on the NFS (PET ~ 20% of the SFS open location), but less shading occurs under the SFS mountain mahogany (PET ~ 40% of the SFS open location). Shallow soil under all vegetation types is typically wetter than at the SFS open location for dry conditions and drier than the SFS open location for wet conditions. Average shallow soil moisture is higher under all vegetation types than in the open, suggesting that the shading effect is stronger than the interception effect for the conditions studied.Item Open Access Enhancement of liquid flow through a leach bed reactor for anaerobic digestion of high solids cattle manure(Colorado State University. Libraries, 2017) Wu, Rongxi, author; Sharvelle, Sybil, advisor; De Long, Susan, committee member; Butters, Greg, committee memberDue to animal production waste increases in Colorado, anaerobic digestion (AD) has become increasingly considered as a technology to convert organic solid waste (OSW) into renewable energy. The arid climate with water resource limitation in Colorado results in high solids cattle manure (HSCM) production, containing between 50% and 90% total solids (TS). Conventional AD for animal manure is best option to treat manure with less than 20% TS, but limited feasibility for conventional anaerobic digesters treats manure in Colorado. The multi-stage anaerobic digester (MSAD) investigated in this study can digest HSCM. An integral part of the MSAD is the Leach Bed Reactor (LBR), which is loaded with HSCM (up to 90% TS). A small quantity of water percolates into the LBR and is recirculated through the LBR where hydrolysis occurs until a large amount of organic material is solubilized into the leachate. A review of the literature has indicated that clogging can be an issue in operation of manure LBRs. Since sustaining liquid flow through LBRs can be a challenge, research was conducted to better understand how to use this technology to treat HSCM. The objectives of this research were to 1) assess the performance of the LBR component of the MSAD technology with different top layer materials and flow regimes to enhance duration of sustained flow, 2) assess the ability of varying top layer materials and flow regimes to enhance hydraulic conductivity of the manure bed in the LBR to maximize hydrolysis in the LBR. For this study, downward flow and upward flow LBR configuration experiments were conducted. The combination of a sand layer on top of the manure beds and an improved top filter for the LBR was added in the upward flow LBR configuration. HSCM samples from each stage of the experiment were analyzed for TS, fixed solids (FS), and volatile solids (VS), and the leachate samples were analyzed for chemical oxygen demand (COD). The leachate outflow rate and column pressure head were also measured daily. Due to failure of all downward flow experiments, the upward flow LBR configuration was evaluated. The clogging issues and leachate flow through the LBR improved by changing to the upward flow LBR configuration. The average operation time of the upward flow experiment was prolonged to 21 days comparing with downward flow experiment, which operated for an average of only 7 days. The percentage reduction of VS in upward flow experiments was on average above 40% indicating successful hydrolysis in the LBRs, comparable to VS reduction observed by other researchers (Uke and Stentiford, 2012). The COD concentration of the upward flow experiments started at an average of 45 g COD/ L and approached the LST's COD concentration of 10 g COD/L at day 10. This indicates that the MSAD was effectively degrading the HSCM throughout the batch digestion period. The constant pressure head of upward flow experiments indicated that no pressure built up inside the LBRs resulting in improved flow through the manure in these systems. In summary, this research showed that the upward flow LBR configuration with the combination of a sand layer on top of the manure bed and improved top cap filter can sustain leachate flow through the LBR for 21 days of operation.Item Open Access Evaluating the parameter identifiability and structural validity of a probability-distributed model for soil moisture(Colorado State University. Libraries, 2007) Tripp, Danielle R., author; Niemann, Jeffrey D., advisor; Butters, Greg, committee member; Oad, Ramchand, committee memberModels that use probability distributions to describe spatial variability within a watershed have been proposed as a parsimonious alternative to fully distributed hydrologic models. This study evaluates the performance of a probability-distributed model that simulates local and spatial average soil moisture in a watershed. The model uses well-known expressions for infiltration, evapotranspiration, and groundwater recharge to describe soil moisture dynamics at the local scale. Then, the spatial mean soil moisture is simulated by integrating the local behavior over a probability distribution that characterizes the spatial variability of soil saturation. Ultimately, the model requires time series for precipitation and potential evapotranspiration and calibration of six parameters to simulate the dynamics of the spatial average soil moisture. The model is applied to the Fort Cobb watershed in Oklahoma using one year of data from September 2005 through August 2006. Model performance is evaluated in three main ways. First, the model's ability to reproduce observed local and spatial average soil moisture through calibration is examined. Second, the identifiability and stability of the parameter values are evaluated to assess parameter uncertainty and errors in the mathematical structure of the model. Third, the identifiability and stability of the sensitivities to changes in annual precipitation and potential evapotranspiration are evaluated to assess the impacts of parameter uncertainty and structural errors on forecasts for unobserved conditions. At the local scale, the calibrated model reproduces the soil moisture with a similar degree of accuracy as a more physically-based model (HYDRUS ID), and both models exhibit some structural errors. For the spatial average soil moisture, the calibration is acceptable simulating soil moisture with a similar degree of accuracy as the model applied at the local scale. Among all the parameters, the standard deviation of soil saturation is the most stable and identifiable. The probability-distributed model produces a relatively wide range of plausible sensitivities for both the local soil moisture and the spatial mean soil moisture, suggesting that parameter uncertainty and model structural errors produce significant uncertainty for unobserved conditions.Item Open Access Hydrological assessment of field-scale GeoWaste and waste rock test piles(Colorado State University. Libraries, 2020) Hassanzadeh Gorakhki, Mohammad Reza, author; Bareither, Christopher, advisor; Shackelford, Charles, committee member; Scalia, Joseph, committee member; Heyliger, Paul, committee member; Butters, Greg, committee memberMine waste rock and mine tailings are generated in substantial quantities an d must be managed to protect human health and the environment. Challenges in mine waste management facilities include geotechnical stability, environmental contamination, water management, and post operation (long term) closure. Waste rock and tailings co-disposal is a management technique that can address many of the aforementioned challenges. GeoWaste is a mixture of fast-filtered tailings and waste rock blended to isolate waste rock particles within a tailings-dominated matrix. A field-scale experiment that included a waste rock pile and GeoWaste pile was conducted at a mine in Central America to evaluate if GeoWaste suppresses sulfide oxidation and production of metal-rich acid rock drainage relative to waste rock. The objectives of this study were to (i) evaluate hydrologic performance of the piles, (ii) conduct in situ infiltration tests on the piles, (iii) determine field-scale hydraulic parameters for GeoWaste and waste rock, and (iv) develop numerical models to predict water content and oxygen concentrations within the piles. Water content, temperature, electrical conductivity, and oxygen concentration within the piles were monitored for 26 months. Sealed double ring infiltrometer tests were conducted at the end of the pile experiment and test pile subsequently were excavated to assess the spatial distribution in geotechnical characteristics. Inverse modeling was completed in HYDRUS-2D based on infiltration data to determine hydraulic conductivity and moisture retention parameters for the test piles. Field- and laboratory-scale hydraulic parameters were used in HYDRUS-1D and HYDRUS-2D to develop seepage models to predict moisture movement during the 26-month pile experiment. Oxygen concentration was predicted for the GeoWaste pile in HYDRUS-1D via the solute transport module, Fick's 2nd law, the oxygen consumption rate, oxygen diffusion in gas and water phases, and Henry's constant.Item Open Access Local understanding of hydro-climate changes in Mongolia(Colorado State University. Libraries, 2012) Sukh, Tumenjargal, author; Fassnacht, Steven, advisor; Laituri, Melinda, committee member; Fernandez-Gimenez, Maria, committee member; Butters, Greg, committee memberAir temperatures have increased more in semi-arid regions than in many other parts of the world. Mongolia has an arid/semi-arid climate where much of the population is dependent upon the limited water resources, especially herders. This paper combines herder observations of changes in water availability in streams and from groundwater with an analysis of climatic and hydrologic change from station data to illustrate the degree of change of Mongolian water resources. We find that herders' local knowledge of hydro-climatic changes is similar to the station based analysis. However, station data are spatially limited, so local knowledge can provide finer scale information on climate and hydrology. We focus on two regions in central Mongolia: the Jinst soum in Bayankhongor aimag in the desert steppe region and the Ikh-Tamir soum in Arkhangai aimag in the mountain steppe. As the temperatures have increased significantly (more in Ikh-Tamir than Jinst), precipitation amounts have decreased in Ikh-Tamir which corresponds to a decrease in streamflow, in particular, the average annual streamflow and the annual peak discharge. At Erdenemandal (Ikh-Tamir) the number of days with precipitation has decreased while at Horiult (Jinst) it has increased. Herders observed that the amount of precipitation has decreased (71% in Jinst; 100% in Ikh-Tamir) in recent years. The long-term average streamflow of the Tuin River at Jinst has not changed significantly while the herders have seen a depletion of water resources (73% of respondents). The Khoid Tamir River at Ikh-Tamir has seen a statistically significant decline in the average annual streamflow and the annual maximum daily discharge, which was also observed by all herders surveyed.Item Open Access Method comparison for analysis of LNAPL natural source zone depletion using CO₂ fluxes(Colorado State University. Libraries, 2015) Tracy, Melissa Kay, author; Sale, Tom, advisor; Blotevogel, Jens, committee member; Butters, Greg, committee memberAccidental releases of subsurface petroleum hydrocarbons, widely referred to as Light Non-Aqueous Phase Liquids (LNAPLs), are a common occurrence in the industrial world. Given potential risks to human health and the environment, effective remediation approaches are needed to address impacts. Natural source zone depletion (NSZD) is a remedial approach gaining wide acceptance, wherein natural mechanisms in the subsurface act to deplete LNAPL in the source zone. Recent research indicates biodegradation of contaminant-related carbon results in a predominantly upward flux of carbon through the vadose zone. Building on this concept, three methods have recently emerged to quantify rates of NSZD using soil gas fluxes; these include the gradient, chamber, and trap methods. Unfortunately, side-by-side field applications of the methods have shown differing estimates of NSZD, leaving concerns about method comparability. The primary objective of this thesis was to conduct a laboratory comparison of the gradient, chamber, and trap methods using uniform porous media, constant environmental conditions, and a known CO₂ flux (i.e., ideal conditions). Given these experimental conditions, challenges associated with field comparisons could be minimized and the fundamental accuracy of the methods could be resolved. Preliminary efforts were also made to understand the effect of surface wind on the accuracy of the methods. A large-scale column (1.52 m high x 0.67 m ID) was filled with dry, homogenous, well-sorted fine sand. Known CO₂ fluxes were imposed through the bottom of the column spanning a range typical of contaminant-related CO₂ fluxes observed at field sites (3.3-15.2 μmol/m²/s). Results under ideal experimental conditions indicated that on average, the chamber and trap methods accurately captured the imposed flux to within ± 7% of the true value, and the gradient method underestimated the imposed flux to within 38% of the true value. Accuracy of the gradient method was largely dependent on estimates of effective diffusion coefficients. Consistent underestimation of the true flux using the gradient method was attributed to the method only quantifying diffusive gas transport. Considering the accuracy of measurements for other subsurface processes (e.g., hydraulic conductivity), the range of accuracy observed among all methods is not surprising. Surface winds were simulated by placing a fan on top of the column; achieved wind speeds ranged from 2.2-5.4 m/s. Laboratory studies identified that all methods were adversely affected by wind; however, the magnitude of laboratory results may have been exaggerated relative to what would be expected at field sites due to the laboratory sand being dry. Wind speeds within the tested range caused the gradient method to further underestimate the true flux to within 44% of the true value. The chamber method underestimated the true flux by 45-47% and 78% for wind speeds ranging from 2.2-3.6 m/s and 4.5-5.4 m/s, respectively. Wind had the opposite effect on the trap method, causing overestimations of the true flux by 60% and 122% for wind speeds ranging from 2.2-3.6 m/s and 4.5-5.4 m/s, respectively. Given similar results under ideal experimental conditions, wind and other environmental factors common to field conditions are suspected to be the primary cause of disagreement observed in side-by-side comparisons of the methods at field sites. Each method has advantages and limitations for field application. Method selection should be predominately driven by site-specific attributes, including environmental factors that may make one method more applicable over another for a given field site. Further consideration of all methods under environmental conditions may provide greater insight into potential biases and support additional recommendations for method selection. Secondary objectives included efforts to test design features specific to the trap method to support continued method development and to advance a model to describe steady-state advective and diffusive transport of a compressible gas through porous media. Results from trap modification studies suggested certain design features of the trap method may have affected the accuracy of measurements. Additional research and method development for the trap method could be undertaken to resolve issues raised in this thesis. Results from modeling efforts suggested gas transport was primarily diffusion driven, accounting for approximately 58-79% of transport, depending on estimates of the effective diffusion coefficient. Analytical modeling did not indicate an appreciable difference in advective and diffusive contributions to gas transport as the imposed flux was varied; however, measured concentration gradients counterintuitively indicated the advective contribution to transport increased as the imposed flux decreased.Item Open Access Method development for long-term laboratory studies evaluating contaminant assimilation processes(Colorado State University. Libraries, 2016) McSpadden, Rachael Lynne, author; Sale, Tom, advisor; Blotevogel, Jens, committee member; Butters, Greg, committee memberRemediation technologies for soil and groundwater that are impacted by chlorinated solvents are limited when reducing contaminant concentrations below maximum contaminant levels (MCLs) established by the US Environmental Protection Agency (EPA). The limited effectiveness of current technologies is partly due to well-documented contaminant back diffusion from low-permeability (k) zones causing long-term impacts on water quality. Back diffusion out of low-k zones for extended periods of time, give strong evidence that assimilation processes are driving the fate and transport of chlorinated solvents within low-k zones. The direct impacts assimilation processes, such as sorption and degradation, have on contaminant concentrations may be slow and negligible on shorter time scales. But for longer time scales assimilation processes could have consequential effects on sites where groundwater concentrations are predicted to exceed MCLs for decades to centuries. Research studies located in the field have been carried out to study assimilation processes in low-k zones. The challenge of such field studies is capturing complete data sets from complex field environments. The challenges include inability to close the mass balance, confidently identifying assimilation mechanisms at work, and are limited to short term studies. Thus, the overall objective of this research is to advance the current knowledge of assimilative processes within low-k zones through the application of long-term (~5-10years) laboratory studies. The goal of the research presented herein, is to create a starting point for long-term laboratory studies in the hopes to quantify assimilation processes within low-k zones. Prior to conducting long-term laboratory experiments, a necessary step of establishing and testing methods need to be conducted. The research described within this thesis applies the use of short-term laboratory studies conducted over a 2 to 3 month time span to test preliminary methods, establish baseline data, and test applicability of mathematical models. The model contaminant used for the short-term laboratory experiments was tetrachloroethene (PCE). For the beginning stages of method development, the assimilation process that was isolated and focused on was sorption. Sorption was evaluated in porous media of differing properties, which included four field soils (Soil A, B, C, and D) and one lab grade soil (LGS). Two short-term column studies were tested to evaluate for viability in collecting data to be used in capturing transport and assimilation processes for use in long-term laboratory studies. The two short-term column study methods are identified throughout this document as headspace vials and ampules. The design setup for both column studies were constructed to utilize diffusive transport of contaminant with a saturated lower boundary layer of PCE, an initially clean water saturated soil column, and headspace at the upper boundary layer. For each column study design, the contaminant is transported via passive diffusion, starting from a volume of high concentration (at the lower boundary layer) to a place of low concentration (throughout the clean soil and the top of the headspace to the clean upper boundary layer). The difference between the two short-term column studies is the method of data collection. The headspace vial method allows for non-destructive sampling of the headspace over time to quantify the diffusive transport of PCE through the soil column. The ampule method utilizes a completely closed system with a destructive sampling technique where the entire ampule is extracted within methanol to help eliminate the potential for mass lost from the system due to volatilization. In addition to the two short-term column studies, batch sorption studies were conducted to gain independent measurements of sorption parameters for the four field soils used throughout the column experiments. Lastly, a numerical solution to the diffusive transport partial differential equation was developed using Mathcad™. Three sorption models are employed: linear, Freundlich and Langmuir models. The parameter values from the batch sorption study were used as inputs for the mathematical model and results were compared to the short-term column study headspace vial experiment. Results from the short-term column studies show that losses from headspace vials may limit the values of the method over time periods greater than one week, but ampules are more stable than headspace vials and show the most potential for application in long-term laboratory studies. Batch sorption studies can complement the diffusive-transport studies by allowing for resolution of sorption parameter values that are independent of transport rates. The validity of the model appears to be challenged by unaccounted losses from the headspace vials, and was therefore unable to estimate experimental data results. The results of the ampules and batch sorption studies are suggested to be used to aid in the design of the long-term studies. The laboratory experiments and modeling described herein will, in hopes, be a step closer to advance the knowledge of assimilative processes and assist in determining the assimilative capacity of low-k zones. Ultimately, this work will hopefully contribute to improved decision-making at contaminated sites, possibly allowing money spent on ineffective remedies to be directed toward more productive solutions.Item Open Access Oleophilic bio barriers (OBBs) for control of hydrocarbon sheens at groundwater-surface water interfaces(Colorado State University. Libraries, 2015) Chalfant, Marc William, author; Sale, Tom, advisor; Butters, Greg, committee member; Gooseff, Michael, committee memberSheens are a common problem at petroleum facilities located adjacent to surface water bodies. Thin, iridescent films of Non-Aqueous Phase Liquid (NAPL) can form on surface water sporadically and unpredictably via three processes: seeps, ebullition, and/or shoreline erosion. Because the appearance of sheens can elicit a notice of violation of the Clean Water Act, a suite of remedies has been used to address them. Common remedies are often predicated on physical barriers and sorbent barriers, both of which can be expensive and/or prone to failure due to bypass and/or finite storage capacities. Groundwater-Surface water Interfaces (GSIs) are active biological zones where NAPL fluxes are attenuated via aerobic biological degradation. Physical and sorptive barriers can inhibit aerobic degradation processes by causing NAPL to accumulate, preventing oxygen delivery or introducing organic matter that exerts an oxygen demand. Shortcomings of current sheen remedies motivate the research presented herein, exploring the concept of aerobic reactive barriers at GSIs. Specifically, the concept of an Oleophilic Bio Barrier (OBB) is advanced. An OBB prevents sheens due to seeps, ebullition, and erosion by employing 1) an oleophilic geocomposite to sorb NAPL, 2) aerobic degradation of NAPL via naturally occurring microbes, and 3) structural cover to mitigate erosion. A full US patent detailing these concepts was submitted to the US patent office in September 2014 (Zimbron et al., 2014). The work presented herein includes laboratory studies, a preliminary field study, a full-scale field demonstration and a general estimate of construction costs. Results of the lab studies provided proof-of-concept that a geocomposite material in an OBB could prevent sheens. The geocomposite was shown to have a capacity of 3L of NAPL/m². The geocomposite was also shown to reduce dissolved hydrocarbon concentrations by up to 77%. The preliminary field study showed that an OBB could be used to prevent sheens in a field setting. Four 1m x 1m OBBs were installed in March 2013 and monitored through August 2013. In August, NAPL saturations of up to 1.6 L/m² were measured in the OBBs, demonstrating their ability to prevent sheens. The geocomposite maintained structural integrity, suggesting chemical compatibility with the NAPL. A low redox potential (62 mV) and the presence of dissolved iron (9.0 mg/L) at 90 cm depth showed that subsurface sediments were anaerobic. Redox potentials ranging from 302 to 423 mV were measured in the OBB water, demonstrating that aerobic degradation could occur and deplete NAPL on the OBBs. Results from the full-scale (36 ft x 18 ft) OBB module study demonstrated sheen prevention and microbial activity. Of 26 visual inspections for sheens, no sheens were observed sourcing from the OBB, while 3 inspections yielded sheen observations on adjacent shoreline. Seasonal changes in sorbed NAPL composition were consistent with patterns of microbial degradation and correlated to decreased redox potentials and warm temperatures. Microbial populations in the OBB were comparable to adjacent and underlying sediments but showed increased diversity of hydrocarbon-degrading microbes. In addition, structural cover was shown to mitigate erosion associated with ice-scour, while sustaining minimal damage and sedimentation. Costs for OBB construction were estimated to be on the order of $100,000 per acre, making more affordable than organoclay barriers and sheet pile barriers. The primary conclusion of this thesis is that OBBs are a viable technology from both cost and performance perspectives. Recommendations for future work include OBB design modifications for improved sediment control, greater compatibility with natural environments, and enhanced NAPL retention capacity. Simplified performance monitoring, research on governing processes, methods for characterizing sheen sources, and the development of a model to support OBB design optimization are also recommended. Ongoing consideration of expanding the full-scale OBB module and active consideration of OBB remedies at other sites provide promising opportunities for further development.Item Open Access Pore fluid salinity effects on sedimentation and geotechnical properties of fine-grained soils(Colorado State University. Libraries, 2015) H. Gorakhki, Mohammad R., author; Bareither, Christopher A., advisor; Shackelford, Charles D., committee member; Butters, Greg, committee memberThe objectives of this study were to evaluate the effects of soluble salt concentration (i.e., salinity) on geotechnical characteristics and sedimentation behavior of fine-grained soils (e.g., mine tailings) and identify test methods applicable for characterizing high-saline soils. Three fine-grained soils were used in this study: soda ash mine tailings, kaolin clay, and bentonite clay. The soda ash mine tailings (sodium carbonate) contained high-saline pore fluid and predominantly sodium on the exchange complex, whereas commercially-available kaolin and bentonite clay were used for comparison with the soda ash tailings. Salinity was controlled in the natural clays via adding salts with different valence (NaCl, CaCl₂, and FeCl₃) at concentrations ranging between 1 and 1000 mM. Salinity in the soda ash tailings was altered via extracting salts from solution using dialysis to create materials with different soluble salt concentrations. Sedimentation experiments were conducted in 63.5-mm-diameter by 457-mm-tall glass cylinders to evaluate the sedimentation rate and final solids content. The effects of pore fluid salinity on geotechnical characteristics of soda ash mine tailings and laboratory-prepared, sedimented soils were evaluated via measuring Atterberg limits, specific gravity, and particle-size distribution via hydrometer tests. Overall, an increase in ionic strength of the sedimentation fluid (i.e., increase in salt concentration) yielded higher sedimentation rates and larger volumes of released water for experiments on bentonite. In contrast, the sedimentation rate of kaolin was constant for salt concentrations between 1 and 100 mM, and the sedimentation rate decreased at higher salt concentrations. This behavior was attributed to an increase in fluid density and viscosity at high salt concentrations that reduced sedimentation. Soda ash sedimentation behavior was similar to kaolin and characterized by a decrease in sedimentation rate with increase in salt concentration. Geotechnical characterization of all materials indicated that liquid limit, plastic limit, and clay content decreased with increasing pore fluid salinity. Temporal evaluations of soil plasticity suggest that hydration times of at least two days are required to solubilize salts and capture salinity effects on soil plasticity. Additionally, experimental methods were developed and evaluated for correcting errors in hydrometer and specific gravity tests that may originate in the presence of soluble salts.Item Open Access Recreating peatland initiation conditions: methods for reclaiming peatlands in Alberta's oil sands region(Colorado State University. Libraries, 2014) Borkenhagen, Andrea K., author; Cooper, David J., advisor; Paschke, Mark, committee member; Butters, Greg, committee memberNorthern Alberta's oil sands deposit is the largest in the world and mining operations remove vast areas of upland forests and peatland ecosystems. Reclaiming peatland ecosystems is challenging as it takes thousands of years to reestablish peat soils to pre-disturbance extents. Practical approaches that are easy to implement are required to reclaim the tens of thousands of peatland hectares that have been lost to mining activities. My research focuses on developing reclamation methods that recreate peatland initiation conditions on mineral soil and apply assisted succession techniques by introducing mosses, plants and woody cover. I evaluated the regenerative abilities of five common fen mosses introduced in a 1:10 mixture to clay loam mineral soil. To evaluate optimal hydrologic conditions for moss species establishment, I tested four water levels below the soil surface (0, -10, -20, and -30 cm). I recreated plant communities and microclimates similar to those found during peatland initiation to determine those that increased moss species establishment by comparing cover treatments of herbaceous plants, woody plants, and WoodStraw® (wood-strand) mulch. After two seasons of growth, fen mosses established and grew to an average of 20 percent cover on mineral soils. Total moss cover was not significantly different between 0cm and -30 cm water levels but species distribution was as depth to the water table was the most important factor influencing establishment. Drepanocladus aduncus was most common when the water level was 0 cm and Aulacomnium palustre was most common in the -30 cm water level. Tomentypnum nitens had five times greater cover than any other moss. Moss species cover and height was greatest under herbaceous plants and at 0 cm water level. Wood-strand mulch reduced the cover of salt that precipitated on the soil surface, which also increased as the water table deepened. Implications to peatland reclamation include selecting a mixture of mosses to adapt to chemical and hydrologic variations and planting herbaceous plants and or applying wood-strand mulch to improve moss establishment on mineral soil. Peatlands may take thousands of years to develop, but reclaiming a carbon-accumulating ecosystem and establishing the foundations for peatland succession is possible. The applications described here provide economical and practical strategies to reconstruct pre-existing peatland ecosystems in Alberta's oil sands region.Item Open Access Spatial variability of snow depth measurements at two mountain pass snow telemetry stations(Colorado State University. Libraries, 2012) Blumberg, Evan J., author; Fassnacht, Steven, advisor; Laituri, Melinda, committee member; Butters, Greg, committee memberMuch of the Western United States relies heavily on spring snow melt runoff to meet its industrial, agricultural, and household water needs. Water professionals use the network of snowpack telemetry (SNOTEL) stations to help forecast spring melt water runoff. These stations only represent a small area and across a watershed, the variability in snowpack properties can be large. Properties such as snow depth can vary substantially even over distances as short as a meter. Previous studies have examined how snow depth is distributed across the landscape and how terrain and vegetation parameters can be used as surrogates for the meteorological variables that drive the distribution of snow. The parameters are derived from a digital elevation model (DEM) that is now at a 30x30m resolution, and they include elevation, aspect, slope angle, and canopy cover, as well as clear sky solar radiation and the maximum upwind slope. Typically three to five snow depth measurements are taken to represent each 30x30m DEM pixel. This study examines the distribution of variability in snow depth within a pixel. Snow depth surveys were conducted around the Joe Wright SNOTEL station near Cameron Pass in northern Colorado on May 1st, 2009 and May 1-2, 2010 and around the Togwotee Pass SNOTEL station in north-central Wyoming on March 17th 2009. Surveys were performed by taking snow depth measurements in a 1 x 1 kilometer block around each SNOTEL station. Due to the logistics of sampling these two locations that both have dense forests and steep terrain, three different sampling methods were employed based on a standard of three points in a row spaced 5 meters apart. To examine the variability at a location (pixel), at least eight additional measurements were taken between the three points (11 points were taken on May 1st, 2009 at Joe Wright). At Togwotee Pass, 10 additional depth measurements were taken about the mid-point, perpendicular to the main transect, yielding 21 points. For the 2010 survey at Joe Wright, the 11 points in a row were supplemented by two points at the beginning, middle and end (three standard points) to yield 17 measurements at a location. From these data the parameters most strongly correlated with the average snow depth, the standard deviation of snow depth, and the coefficient of variation were computed. Binary regression trees were used to further explore the relation between the average and variability and the terrain and canopy parameters. The statistics (average and standard deviation) from the standard three points was compared to all the points (11, 17or 21) measured at a location. Data were sub-set from all the points to determine the average difference and subsequently an appropriate number of depth measurements that should be taken to represent a location. Key variables were not consistent for the 2009 and 2010 Joe Wright SNOTEL surveys, and also varied when looking at standard deviation or coefficient of variation. Among many surveys, canopy cover, elevation, and sin of slope were key variables, but to different degrees. Investigation into survey efficiency show that taking between 3 to 6 data points per pre-determined sample point is suitable to be within 5% of the overall average, whether it be the 11, 17, or 21 point survey scheme.Item Open Access Stochastic analysis of flow and salt transport modeling in irrigation-drainage systems(Colorado State University. Libraries, 2012) Alzraiee, Ayman H., author; Garcia, Luis A., advisor; Gates, Timothy K., advisor; Bau, Domenico, committee member; Butters, Greg, committee memberSustainability of crop production in the Lower Arkansas River Basin in Colorado is seriously threatened by the continuous degradation of irrigated lands by the dual impact of soil salinization and waterlogging problems. Integration of improved irrigation practices, upgrades to the irrigation systems, and subsurface drainage are essential components of any plan to stop the deterioration of irrigated lands. Numerical simulations of irrigation and drainage systems are necessary to justify the consequent management actions. Despite the uncertainty of their predictions, numerical models are still indispensable decision support tools to investigate the feasibility of irrigation and drainage systems management plans. However, the uncertainties in input parameters to these models create a risk of misleading numerical results. That is beside the fact that the numerical models themselves are conceptual simplifications of the complex reality. The overarching objective of this dissertation is to investigate the impact of parameters uncertainty on the response of simulated irrigation-drainage systems. In the first part of the research, a Global Sensitivity Analysis (GSA) is conducted using a one-dimensional variably saturated problem to prioritize parameters according to their importance with respect to predefined performance indices. A number of GSA methods are employed for this purpose, and their comparative performances are investigated. Results show that only five parameters out of 18 parameters are responsible for around 73% of crop yield uncertainty. The second part introduces a method to reduce the computational requirements of Monte Carlo Simulations. Numerical simulation of variably saturated three-dimensional fields is typically a computationally intensive process, let alone Monte Carlo Simulations of such problems. In order to reduce the number of model evaluations while producing acceptable estimates of the output statistical properties, Cluster Analysis (CA) is used to group the input parameter realizations, e.g. hydraulic conductivity. The potentials of this approach are investigated using different: 1) clustering schemes; 2) clustering configurations, and 3) subsampling schemes. . Results show that response of 400 realizations ensemble can be efficiently approximated using selected 50 realizations. The third part of the research investigates the impact of input parameter uncertainty on the response of irrigation-drainage systems, particularly on crop yield and root zone hydrosalinity. The three-dimensional soil parameters, i.e. hydraulic conductivity, porosity, the pore size distribution (van Genuchten β) parameter, the inverse of the air entry pressure (van Genuchten α) parameter, the residual moisture content parameter, and dispersivity; are treated as spatial random processes. A sequential multivariate Monte Carlo simulation approach is implemented to produce correlated input parameter realizations. Other uncertain parameters that are considered in the study are irrigation application variability, irrigation water salinity, irrigation uniformity, preferential flow fraction, drain conductance coefficient, and crop yield model parameters. Results show that as the crop sensitivity to salinity increases, the crop yield standard deviation increases. The fourth part of the research investigates an approach for optimal sampling of multivariate spatial parameters in order to reduce their uncertainty. The Ensemble Kalman Filter is used as instrumentation to integrate the sampling of the hydraulic conductivity and the water level for a two-dimensional steady state problem. The possibility of combining designs for efficient prediction and for efficient geostatistical parameter estimation is also investigated. Moreover, the effect of relative prices of sampled parameters is also investigated. A multi-objective genetic algorithm is employed to solve the formulated integer optimization problem. Results reveal that the multi-objective genetic algorithm constitutes a convenient framework to integrate designs that are efficient for prediction and for geostatistical parameter estimation.Item Open Access Water quality benefits of wetlands under historic and potential future climate in the Sprague River Watershed, Oregon(Colorado State University. Libraries, 2013) Records, Rosemary M., author; Fassnacht, Steven, advisor; Arabi, Mazdak, advisor; Duffy, Walter, committee member; Butters, Greg, committee memberAn understanding of potential climate-induced changes in stream sediment and nutrient fluxes is important for the long-term success of regulatory programs such as the Total Maximum Daily Load and sustainability of aquatic ecosystems. Such changes are still not well characterized, particularly in the Pacific Northwest, although shifts in stream flow associated with warming temperatures have already been observed in the region. Conservation practices such as wetland restoration are often regarded as important in watershed-scale management of water quality. However, the potential of wetland gains or losses to alter future stream water quality conditions has received relatively little study. The primary goal of this research is to assess the basin-scale regulation of sediment, nitrogen and phosphorus provided by variable wetland extent under current climate and potential mid-21st century climate. Specific objectives of the study are (1) to evaluate the effects of present-day wetlands on stream water quality under current climate; (2) to identify direction and magnitude of potential changes in stream flow, sediment, and nutrient loads under present-day wetlands and potential future climate; and (3) to determine how wetland gain or loss might exacerbate or ameliorate climate-induced changes in future water quality. These objectives are investigated with the Soil and Water Assessment Tool (SWAT) hydrologic model in the Sprague River watershed in southern Oregon, United States, which has been historically snowmelt dominated and where elevated nutrient loads in the 20th century have contributed to decline of fish species downstream. Results suggest that present-day wetlands under current climate may result in substantially lower nitrogen and phosphorus loads at the Sprague River watershed outlet. SWAT simulations forced with precipitation and temperature from six General Circulation Model (GCM) derived climate projections for 2030-2059 suggest uncertainty in magnitude and direction of both precipitation and stream flow changes on an average annual and monthly basis. Under present-day wetland extent, long-term average annual runoff for 2030-2059 decreased by 4% under one projection relative to a baseline period of 1954-2005, but increased by 6-31% under other projections. However, change in future annual runoff was statistically different from baseline for only two of six climate projections. Late spring and summer stream flow was lower in all simulations but significantly different from baseline in only some cases; for simulations driven with wetter future climate projections average monthly flow increased significantly from approximately October through March, and peak average monthly flow increased from 3-36% but timing did not alter. A simulation driven with a drier future climate projection showed decreases in average flow for most months, but was not significantly different from baseline. Simulated average annual sediment and nutrient loads generally tracked flow seasonality and decreased by 6% (sediment), 8% (TN) and 11% (TP) under one projection, but increased from 7-52% (sediment), 4-37% (TN) and 1-38% (TP) under other projections. Findings suggest that nutrient loads at the Sprague River outlet under future climate and scenarios of wetland change could vary significantly from baseline, or could be similar to the historic period. However, a threshold of wetland loss may exist beyond which large increases in nutrient loads could occur, and wetland gain might do little to ameliorate climate impacts to stream water quality in the Sprague River watershed.