Mountain Scholar :: Browsing by Author "Butters, Gregory, committee member"

Browsing by Author "Butters, Gregory, committee member"

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Open Access
Assessing flow alteration and channel enlargement due to dam management at Hog Park Creek, Wyoming
(Colorado State University. Libraries, 2016) Carleton, Tyler J., author; Fassnacht, Steven R., advisor; Butters, Gregory, committee member; Stednick, John D., committee member
As part of a complex water exchange agreement, Little Snake River water is piped through the Continental Divide and released into Hog Park Creek to replace over-appropriated North Platte River piped to Cheyenne, Wyoming. The Little Snake River water, in addition to native flows, has used Hog Park Creek as a conduit since the 1960s. As a result, Hog Park Creek has continued to enlarge. This study assesses flow alterations and channel enlargement at Hog Park Creek due to dam management. To assess flow alterations at Hog Park Creek without a pre-dam daily flow record, the Precipitation-Runoff Modeling System (PRMS) simulated natural flows from 1995 to 2015. A regionalization technique transferred calibrated parameters to Hog Park Creek model parameterization from Encampment River model parameterization. Along with the simulated natural flows, reference flows were used to compare to the post-dam flow record. All comparisons indicate the greatest flow alterations were winter and spring monthly flows and low flows. The April median flows and 7-day low flows more than tripled. To a lesser degree of deviation, significant flow alterations included peak flow alterations such as greater magnitude, longer duration, increased frequency, earlier peak flow timing, and faster fall rates. In addition, flow alterations due to climate were assessed. The climate trends reflect warmer-wetter climate change with a shift to earlier peak flows. However, these flow alterations are minor compared to those by dam management. The climate projections compared historic (1980-1999) and future (2040-2059) PRMS simulated natural flows using warmer-wetter and -drier scenarios. Both scenarios project more frequent, flashier peak flows. The warmer-wetter scenario also projects a shift to earlier peak flows. This projected shift of peak flows to mid-May is earlier than the current artificial peak flows in late-May and the natural peak flows in early June. Channel enlargement measured at Hog Park Creek is consistent with qualitative channel response for increased flows and sediment loads less than sediment transport capacity. Stream surveys from 2006 and 2015 measured irregular channel widening and bed degradation. The riffle cross-sections (XSs) measured little change while pool XSs at the maximum point of scour measured extensive widening (+ 3.6 m). Ecologic implications of continued channel enlargement were evaluated by modeling changes in water surface elevations using the Hydrologic Engineering Center River Analysis System (HEC RAS). Between 2006 and 2015, modeling indicated a decrease in water surface elevation by 3 cm per decade and a decrease in flood inundation area of 70 m2 per 1 m of stream length per decade. Additionally, the hydraulic modeling results support the theory that alluvial channel form is most influenced by bankfull flow, which in this case is the 1.5-year flood. Based on this agreement, modeling indicated channel enlargement began near a pre-dam bankfull flow of 3.8 m3 s-1 (135 ft3 s-1) and has since increased to 5.5 m3 s-1 (195 ft3 s-1) in 2015. A possible trajectory of channel enlargement is to a bankfull flow of 5.8 m3 s-1 (205 ft3 s-1), which is based on the 1.5-year flood since dam enlargement in the 1980s. However, without a stable flow regime, a stable channel form is not possible. Thus, to improve aquatic and riparian habitat, a stable flow regime and channel form will be necessary. For this reason, recommendations for a modified flow regime based on the findings of this study are developed and can be used as guidance for adaptive management.
Open Access
Assessing the on-farm effects of removing salts from irrigation water
(Colorado State University. Libraries, 2023) Shrestha, Sanskriti, author; Bailey, Ryan, advisor; Sharvelle, Sybil, committee member; Butters, Gregory, committee member
In dry and semi-arid places where precipitation is insufficient to sustain a regular percolation of water through the soil, salt-induced land degradation is frequent. Desalination of irrigation water is an emerging alternative that can be utilized to repurpose our salt-affected agricultural lands, thus providing an avenue for sustaining the growing production demands with limited water and land resources. Therefore, a combination of fieldwork, modeling and soil sensor records was implemented to evaluate the feasibility of an on-farm Reverse Osmosis (RO) system, in terms of crop yield and soil salinity, for the desalination of irrigation water over three growing periods. Four types of treatment systems were applied to 16 experimental field plots at the Arkansas Valley Research Center (Rocky Ford, CO), representing soil conditions of the Lower Arkansas River Valley (LARV), a region of which approximately 70% is affected by salt-induced crop yield loss. Statistical t-tests done on the data of the three seasons did not show any significant differences in the VMC, EC and biomass of the plots irrigated with the different treatments. Results of the tests for season 3, which showed an increase in t-values and a decrease in p-values demonstrated the need for a longer study period to gauge any significant effects. Similarly, the results of sensor data did not show a significant decrease in soil salinity for the study period. The average soil electrical conductivity (EC) showed a 20% to 26% reduction in soil salt mass in the fields irrigated with desalinated water over the three seasons, however, the EC results did not show a consistent decreasing trend across the 16 plots. A 6-year numerical modeling forecast done by the hydro-chemical model HYDRUS 1D simulating dry, average, and wet weather showed a 6% to 20% reduction in EC when desalination was applied to the fields. These preliminary results of the field and modeling approaches provide encouragement for the continuation of desalination treatments to see any substantial long-term effects.
Open Access
Biotic control of LNAPL longevity - laboratory and field- scale studies
(Colorado State University. Libraries, 2017) Emerson, Eric Douglas, author; De Long, Susan K., advisor; Sale, Thomas, advisor; Butters, Gregory, committee member
Natural source zone depletion (NSZD) is an emerging strategy for managing light nonaqueous phase liquids (LNAPLs). Unfortunately, little is known about NSZD rates over extended periods of time, where heterogeneous redox conditions and changing LNAPL saturations may influence processes governing losses. Understanding long-term rates is central to anticipating LNAPL longevity under both natural and engineered conditions. Herein, laboratory and field-scale modeling studies were conducted to evaluate LNAPL longevity. Laboratory studies evaluated loss rates as a function of total contaminant concentration under sulfate-reducing (SR) and methanogenic (MG) conditions. Biotic and abiotic loss rates were determined via tracking biodegradation products and hydrocarbons in column effluents and produced gasses over time. Furthermore, compositional weathering of LNAPL was evaluated. Loss rates with elevated sulfate averaged 39.8 mmole carbon/day/m3 (±9.1 mmole carbon/day/m3). Once sulfate in the soil was depleted to influent water sulfate concentrations of 20 mg/L, subsequent average loss rates were 39.7 mmole carbon/day/m3 (±19.6 mmole carbon/day/m3). Overall, loss rates with and without elevated sulfate were similar. Furthermore, results suggested that loss rates are independent of LNAPL concentration over the range of 9,000 to 37,000 mg/kg and redox conditions observed. Loss rates independent of LNAPL concentrations indicated that biologically mediated NSZD follows zero-order kinetics over the range of conditions evaluated. Column loss rates were compared to field-measured loss rates assuming an LNAPL thickness of three meters. Given this assumption, mean observed early- and late-loss rates are 1.38 and 1.41 μmole carbon/m2/sec, respectively. Assuming decane as a representative LNAPL, observed loss rates are equivalent to 7890 and 8060 L/hectare/year. A column was sacrificed at the completion of the study. Predicted mass losses of the study equate to approximately 1% total initial LNAPL mass lost. Total petroleum hydrocarbons (TPH) soil analysis of initial and final grab samples of column soil did not detect significant mass losses. Moreover, no significant shifts in the LNAPL composition were seen during the course of the study. Mass losses in this range are difficult to accurately quantify via soil-phase hydrocarbon analyses, thus highlighting the utility of the approach used herein. An LNAPL longevity model (The Glide Path Model) was applied at a field site using a zero-order rate model for biological NSZD. LNAPL Longevity ranged from 35 to 105 years using a mean NSZD rate, plus or minus factors of 2 and ½, respectively. Active recovery was shown to have little effect on the longevity of LNAPL.
Open Access
Calibration and uncertainty of a head-discharge relationship for overshot gates under field conditions
(Colorado State University. Libraries, 2019) Kutlu, Caner, author; Gates, Timothy K., advisor; Venayagamoorthy, Karan, committee member; Butters, Gregory, committee member
Adjustable overshot gates (pivot weirs) are commonly used to control discharge and water levels in irrigation water delivery networks. The degree to which this control can be achieved depends upon reliable relationships between flow rate and the hydraulic head upstream and downstream of the gate. Moreover, such relationships also can be used for flow measurements. This study aims to develop a head-discharge equation for free flow over a overshot gate, to describe its uncertainty, and to examine the impact of gate submergence on the equation. Previous research on the flow characteristics of overshot gates has been performed primarily in laboratories, with very little investigation of performance in the field. This thesis provides a report of a field study conducted on four Obermeyer-type pneumatically automated overshot gates, which were operated for irrigation water delivery in northern Colorado. Utilizing both classical and amended forms of the sharp-crested weir equation, Buckingham-Pi dimensional analysis, and incomplete self-similarity theory, head-discharge equations for free flow have been developed which are alternately dependent on and independent of the gate inclination angle. To estimate the flow rate, three fully-suppressed Obermeyer-type overshot gates with crest widths of 22 ft, 20 ft, and 15 ft, and respective lengths of 5 ft., 6.3 ft., 6.08 ft , were inspected for eight different inclination angles (α = 22.8°, 23.6°, 29.7°, 32.6°, 34.6°, 35.3°, 38.9°, 40.4°), under free flow conditions. The best-performing equation is of classical form and contains a discharge coefficient dependent on gate inclination angle. It can be used to relate the discharge to upstream hydraulic head with about ± 10 % (standard deviation range of residual error) for free flow conditions. This equation is applicable for inclination angles between 20° and 40° and for flow rates ranging from 20 to 330 ft3/s. To reduce uncertainty of the discharge coefficient and to prevent the misleading consequences of neglecting the velocity head in the approaching flow, the total upstream energy head was employed in the equation. The effect of velocity head was significant for flow estimation. Dependency of the equation on the gate and field characteristics was examined by testing the equation with field data for a different type of overshot gate. Alternate equations were developed which altered the classical form for a sharp-crested weir to include both a coefficient and an exponent that are dependent upon gate inclination angle, and which preserved the classical form and treated the discharge coefficient as a constant independent of gate inclination. Although, satisfactory results were obtained for these alternative forms, inclusion of the angle in the discharge coefficient alone was recommended for higher accuracy of flow rate estimation, particularly for larger overshot gates with inclination angles ranging from about 20° to about 40°. Furthermore, the modular limit of the overshot gates was investigated for a fourth Obermeyer gate with a crest width of 17 ft and a length of 5.8 ft. Up to a submergence ratio of 0.51, the submergence effect was not observed to decrease the flow rate over for the gate. More data for a higher submergence conditions are required to develop a modular limit and a head-discharge equation for submerged flow.
Open Access
Comparison of alternative estimators of deep percolation in full and deficit irrigation
(Colorado State University. Libraries, 2015) King, Jonathan, author; Sanford, William E., advisor; Butters, Gregory, committee member; Ronayne, Michael, committee member
Farmers are increasingly selling their water rights to growing municipalities and abandoning their farms (buy and dry). A loss of food production in the midst of a growing population is a recipe for food shortages. There is a need for municipalities to meet their water demand from the water rights held by farmers while farmers continue to produce crops. One solution to prevent a 'buy and dry' scenario is for farmers to lease a portion of their water rights to municipalities and continuing to farm under a deficit irrigation program. For this solution to work Colorado Water Law requires that return flows be maintained for down gradient water users. According to Colorado Water Law, deep percolation is any water in the unsaturated zone below the root zone (Colorado Foundation for Water Education, 2009). Deep percolation is also assumed to result in groundwater recharge. The first objective of this study is to quantify deep percolation. The second objective is to determine an optimal deficit irrigation technique. The third objective is to evaluate the methods used to estimate deep percolation. This study investigated three different cornfields (referred to as Blocks) in 2011 in Greeley, Colorado. Each block practices different flood irrigation techniques for the purpose of finding an optimal deficit irrigation plan. Block 2 practices traditional flood irrigation, Block 1 applies water at the same frequency as in Block 2 but uses half the volume of water, and Block 3 only irrigates twice during the growing season but applies large volumes of water per irrigation. Three methods were used to estimate deep percolation in each block: Lysimeters, Unsaturated Zone Water Balance (UZWB), and Darcy Flux. At the same time as this study, the United States Department of Agriculture - Agricultural Research Service (USDA-ARS) estimated deep percolation using a water balance method. The lysimeter method found an average deep percolation for Block 1 at 58mm, Block 2 at 334 mm, and Block 3 at 238 mm. The UZWB method found an average deep percolation for Block 1 at 291mm, Block 2 at 518 mm, and Block 3 at 516 mm. The Darcy flux method found an average deep percolation for Block 1 at 209 mm, Block 2 at 160 mm, and Block 3 at 1,246 mm. The USDA-ARS found an average deep percolation for Block 1 at 391 mm, Block 2 at 838 mm, and Block 3 at 635 mm. Corn was harvested by the USDA-ARS at the end of the season and yields were estimated. Block 1 produced 149 bushels/acre, Block 2 produced 196 bushels/acre, and Block 3 produced 84 bushels/acre. All methods found the irrigation strategy applied to Block 3, in relation to the other Blocks, resulted in the greatest percentage of deep percolation compared to water applied. The lysimeter method determined that the irrigation plan used in Block 1 was the least efficient in creating deep percolation while the UZWB and Darcy Flux method found that the irrigation applied to Block 2 was the least efficient. Although Block 3 was the most effective in producing deep percolation it produced the least amount of corn. The UZWB method was thought to be the most valuable method in this study. Installation of the neutron probe access tubes caused minimal disturbance to the soils and this method investigated the entire unsaturated zone below the zero flux plane, which accounted for most vertical heterogeneity. The lysimeter method was the most direct method, but installation caused extensive soil disturbances. However, once the soil settled over time the lysimeter method provided consistent and reliable results. In this study the Darcy Flux Method provided the greatest range in results compared to the other methods. The primary concern in using the estimates from this method was the quality of the data collected by the sensors.
Open Access
Don't cry over spilled water: identifying risks and solutions for produced water spills
(Colorado State University. Libraries, 2017) Shores, Amanda Rose, author; Laituri, Melinda, advisor; Butters, Gregory, committee member; Pilon-Smits, Elizabeth, committee member; Gooseff, Michael, committee member
Resource requirements and future energy generation requires careful evaluation, particularly due to climate change and water scarcity. This thesis discusses one aspect of energy generation linked to water; oil-and-gas extraction and the large volumes of waste water produced, otherwise known as "produced water". This research focuses on surface spills of produced water, their ramifications, safeguards against groundwater contamination at spill sites and potential remediation strategies. Produced water contains a variety of contaminants that include the group of known toxins, BTEX (benzene, toluene, ethylbenzene and xylene), and high salt concentrations. A combination of factors such as large volumes of generated produced water, the need for storage and transportation across large distances and the toxic-and-mobile nature of produced water constituents creates risks for spills that can pollute groundwater. Spills occur regularly, particularly in Weld County, Colorado, where the demand for natural gas is high. To answer spill-related hypotheses, a multitude of methodology were employed: modeling, greenhouse experimentation, gas chromatography and summarization of spill reports and statistical analyses. Using publicly available spill data, this research found that the frequency of oil-and-gas related spills and the average spilled volume has increased in Weld County from 2011–2015. Additionally, the number of spills that have resulted in groundwater contamination has increased in the area. By focusing on the oil-and-gas operators responsible for these spills, a linear relationship was found between the volumes of oil-and-gas produced compared to the volumes of produced-water generated. However, larger oil-and-gas producers did not show a linear relationship between oil-and-gas produced and produced-water generated, such that larger producers were more efficient and generated less water per unit of energy. So while scale-up efficiency seems to exist for produced-water generation, no mitigation of spill volume would be obtained by utilizing larger producers. Regardless of which operator was responsible for the spill, the groundwater depth at a spill site significantly predicted when a spill would result in groundwater contamination. This result was also validated though modeling; shallow depths to groundwater as well as larger spill volumes and coarse soil textures contributed to higher concentrations of groundwater contamination. Previous research has shown that a large fraction of spills occur at well pads. Our results suggest that fracking-site selection should preclude areas where the groundwater is shallow and soil is coarsely textured. Additionally, precautions should be taken to reduce the volume of spilled produced water to reduce the risk of groundwater contamination. This research additionally sought to reduce contaminant migration in soils towards groundwater at produced-water spill sites. In a greenhouse study it was shown that foxtail barley (Hordeum jubatum) and perennial ryegrass (Lolium perenne), can tolerate high salt concentrations in produced water while taking up minute levels of BTEX. The presence of plants changed the concentration of BTEX and naphthalene in the soil, but the direction of the change depended upon the particular plant and varied across contaminants. Additionally, the roots of either species saw no decrease of biomass upon exposure to BTEX and salt but shoots biomass was significantly reduced for foxtail barley. These results suggest that these grasses would not be capable of addressing large concentrations of BTEX at spill sites; however, these plants would be useful near well pads that regularly experience smaller spills, thus being able to tolerate spills while continually removing small amounts of BTEX in the soil. In conclusion, this thesis sought to identify holistic tools for produced-water spill prevention, mitigation and remediation to lessen environmental and health concerns while creating minimal disturbance to the natural landscape. The results lend themselves to important management information applicable to Weld County, CO but with lessons that others can draw upon elsewhere. This dissertation highlights areas for improved regulation and best management practices that can preemptively reduce the risk for groundwater contamination from produced water spills.
Embargo
Enhancing rootzone soil moisture estimation using remote sensing, regional characteristics, and machine learning
(Colorado State University. Libraries, 2023) Sahaar, Ahmad Shukran, author; Niemann, Jeffrey D., advisor; Chavez, Jose Luis, committee member; Green, Timothy R., committee member; Butters, Gregory, committee member
Accurate estimation of root-zone soil moisture (θ ̄) is essential for various agricultural applications, including crop yield estimation, precision irrigation, and groundwater management. This dissertation encompasses three interconnected studies that collectively investigate different approaches for improving soil moisture estimation. The first study delves into the utilization of remote sensing methods, particularly optical and thermal satellite imagery, to estimate fine-resolution (30 m) root-zone soil moisture across diverse regions. Traditionally, these methods relied on empirical relationships with evaporative fraction Λ_SEB or evaporative index Λ_PET. However, it has been shown that a single relationship does not universally apply to all regions. This study evaluates the influence of regional soil, vegetation, and climatic conditions on the shape and strength of these relationships using global sensitivity analysis. The results highlight that soil characteristics, such as clay and silt content, and vegetation properties, like leaf area index and rooting depth, play pivotal roles in determining these relationships. Moreover, the impact of annual precipitation in defining climatic regions is crucial. Consequently, region-specific relationships are proposed, adapting to local conditions and potentially enhancing soil moisture estimates. The second study extends this investigation by applying the regionally adapted relationships for the Λ_SEB " vs." θ ̄ and Λ_PET " vs." θ ̄ to estimate rootzone soil moisture (θ ̄) from remote sensing data across four study regions. The results consistently demonstrate the superior performance of the regionally adapted relationships over a single empirical relationship, with a substantial reduction in root mean squared error. These adapted relationships are particularly effective in arid and semiarid regions. The third study explores the application of machine learning models, including XGBoost, CatBoost, RF, LightGBM, and artificial neural networks, to predict soil moisture levels across various climates and depths in the contiguous United States. The findings emphasize the high accuracy and effectiveness of machine learning models, especially XGBoost, in predicting soil moisture across diverse climate regions. XGBoost outperforms other models, making it a potentially valuable tool for soil moisture prediction in environmental monitoring and management. The study also highlights the influence of climate and soil depth on prediction accuracy, with deeper layers having improved forecasts. Additionally, feature importance analysis identifies key predictors for predicting soil moisture, such as elevation, aridity index, soil composition, and depth. These findings contribute to the advancement of soil moisture monitoring and management, with practical applications in agriculture and environmental sciences.
Open Access
Impact of methanotroph ecology on upland methane biogeochemistry in grassland soils
(Colorado State University. Libraries, 2011) Judd, Craig R, author; von Fischer, Joseph C., advisor; Butters, Gregory, committee member; Webb, Colleen T., committee member
Molecular assays of soil environments reveal tremendous microbial diversity, but it remains unclear how this diversity might be mechanistically linked to the ecology of the organisms and their biogeochemical function. Methane consumption in upland soils is arguably the simplest biogeochemical function, and there are emerging patterns in the diversity and biogeography of the organisms that carry out soil methane consumption. This simplicity may allow methane uptake in upland soils to be a model system for merging microbial ecology, diversity and biogeochemistry. Five key traits appear critical for methanotroph ecology: enzyme kinetics, nutrient demand, pH tolerance, ammonium sensitivity and desiccation tolerance. Unfortunately, few studies to date have examined the functional consequences these traits may have on methane consumption. Here, I present analysis of methanotroph community composition and Michaelis-Menten kinetics of methane uptake across three North American temperate grassland sites of differing soil moisture regimes. Across this gradient, I observed distinct variation in community composition, and significant changes in enzyme kinetics. In addition, I find that differences in field estimates of methane activity parallel the patterns of Michaelis-Menten assays, which in turn correlate with differences in methanotroph community composition. These correlations suggest that methanotroph community composition alters ecosystem function.
Open Access
Impacts of precipitation and potential evapotranspiration patterns on downscaling soil moisture in regions with large topographic relief
(Colorado State University. Libraries, 2016) Cowley, Garret S., author; Niemann, Jeffrey D., advisor; Green, Timothy R., committee member; Butters, Gregory, committee member
Mapping of soil moisture is important for many applications such as flood forecasting, soil protection, and crop management. Soil moisture can be estimated at coarse resolutions (>1 km) using satellite remote sensing, but that resolution is poorly suited for many applications. The Equilibrium Moisture from Topography, Vegetation, and Soil (EMT+VS) model downscales coarse-resolution soil moisture using fine-resolution topographic, vegetation, and soil data to produce fine-resolution (10-30 m) estimates of soil moisture. The EMT+VS model performs well at catchments with low topographic relief (≤124 m), but it has not been applied to regions with larger ranges of elevation. Large relief can produce substantial variations in precipitation and potential evapotranspiration (PET), which might affect the fine-resolution patterns of soil moisture. In this research, simple precipitation and PET downscaling methods are developed and included in the EMT+VS model, and the effects of spatial variations in these variables on the surface soil moisture estimates are investigated. The methods are tested against ground truth data at the 239 km2 Reynolds Creek Watershed in southern Idaho, which has 1145 m of relief. The precipitation and PET downscaling methods are able to capture the main features in the spatial patterns of both variables, and the fine-resolution soil moisture estimates improve when these downscaling methods are used. PET downscaling provides a larger improvement in the soil moisture estimates than precipitation downscaling likely because the PET pattern is more persistent through time, and thus more predictable, than the precipitation pattern.
Open Access
Modeling and field evaluation of the strength of surface soils for vehicle mobility
(Colorado State University. Libraries, 2019) Pauly, Matthew J., author; Scalia, Joseph, advisor; Niemann, Jeffrey D., advisor; Green, Timothy R., committee member; Butters, Gregory, committee member
Surficial soil strength is a critical variable in vehicle mobility and terrain trafficability analysis and varies substantially in time and space with soil moisture and texture. Fine-resolution (5-30 m grid cell) patterns of soil strength and soil moisture are necessary for routing of off-road vehicle operations and must be estimated for applications when direct measurement is too expensive, labor-intensive, or dangerous. Rating cone index (RCI) is the in-situ method typically used in mobility applications to empirically evaluate the strength of surficial soils. The RCI method provides one simple parameter to evaluate soil trafficability, but in doing so fails to separately characterize the various mechanisms (compressibility, stress independent shear strength, stress dependent shear strength) that govern soil behavior in relation to vehicle traffic. Alternatively, the Bekker soil strength framework, which encompasses pressure-sinkage and shear strength soil properties, offers a mechanics-based representation of soil behavior and has received increased interest from the terramechanics community in recent years. However, because RCI has been the focus of the terramechanics community over several decades, predictive relationships to estimate Bekker parameters using basic spatially- and temporally-variable input data (soil moisture and soil composition) do not exist. The objective of this study is to develop and evaluate a framework for prediction of Bekker parameters (cohesion and friction angle) as a function of soil moisture and soil texture (percentage of sand and clay). A model, termed the Strength of Surface Soils (STRESS) model, is introduced to estimate shear strength of surface soils using soil moisture, pedotransfer functions based on soil texture, and unsaturated soil mechanics. The STRESS model is paired with an existing soil moisture downscaling model, the Equilibrium Moisture from Topography, Vegetation, and Soil (EMT+VS) model. The pre-existing EMT+VS model includes two untested simplifications that make the model inconsistent with the STRESS model framework, so two previously neglected soil-related hydrologic considerations are introduced to the EMT+VS model: runoff and residual water content. The impacts of runoff and residual on soil moisture downscaling performance and spatial patterns of soil moisture are assessed at a test region in northeastern Colorado called Drake Farm with measured soil moisture data for model calibration and evaluation. The additions are successfully included in the EMT+VS model but the assumptions made in the pre-existing EMT+VS model are shown to be adequate for soil moisture downscaling. After assessing EMT+VS model additions, the STRESS model is applied to Drake Farm to produce spatial patterns of estimated friction angle and cohesion. Model estimates are compared to measured shear strength using a human-powered shear strength bevameter to evaluate the predictive capability of the STRESS model. The model is found to underpredict friction angle and overpredict cohesion at Drake Farm due in part to the use of class-average effective shear strength parameters that do not appear to adequately reflect the properties of surficial soils. Finally, the design and construction of two bevameters are summarized for field and laboratory measurement of Bekker parameters. The results of laboratory tests on the human-powered shear strength bevameter used in STRESS model evaluation are compared to traditional geotechnical strength testing to validate field-testing results and ensure repeatability of measurements. Additionally, the design and construction of a fully automated, laboratory-focused bevameter device with pressure-sinkage and shear strength testing capabilities are described, but this bevameter is not used for testing in this study.
Open Access
Precipitation and temperature changes and their effect on groundwater along the Kona coast of Hawai'i
(Colorado State University. Libraries, 2015) Stevenson, Sharla Ann, author; Fassnacht, Steven, advisor; Kampf, Stephanie K., committee member; Butters, Gregory, committee member
Water resources are an important part of the Hawaiian cultural tradition, and a shift to a warmer, dryer climate may initiate physical and biological changes that would inhibit the practice of Native Hawaiian cultural traditions by altering the coastal ecosystem resources such as those found within Kaloko-Honokōhau National Historical Park. The high degree of spatial heterogeneity and numerous microclimates on the Island of Hawai'i motivated an in-depth analysis of changes in precipitation and temperature occurring during the time since the park was established in 1978 up to the year 2010 at stations located within the regional recharge area for the Kona aquifer system. The potential long-term implications of changes in climate to groundwater recharge were also modeled using stochastic techniques. A statistical analysis was conducted on annual, winter, and summer precipitation and minimum and maximum temperature climate records using the Mann-Kendall test to detect the presence of a monotonic increasing or decreasing trend at significance levels of alpha = 0.1, 0.05, 0.01, and 0.001. The similarities and differences between station records were further evaluated by a double mass analysis of the same precipitation datasets. The changes identified during trend analysis were used to create synthetic realizations of temperature and rainfall patterns 50 years into the future using stochastic modeling techniques. The future realizations were analyzed to evaluate changes in net precipitation and the potential effect on groundwater recharge. Within the Kona aquifer recharge area there is evidence of diverse changes in rainfall that have taken place over recent decades. 13 out of 15 stations evaluated for changes in rainfall have decreasing trends during the 1978 to 2010 time period and over their entire observation record. Decreases in annual rainfall range from 30mm to 250mm per decade with the majority of declines occurring in the summer season. Almost half of the stations had significant changes in rainfall during the summer season, but none of the changes in winter rainfall were significant. The trends displayed in both rainfall and temperature when modeled 50 years into the future indicate declines in net precipitation ranging from 6 to 48% compared to the modeled stationary 50 year mean. All of the modeled scenarios indicated a decline in the number of days with rainfall for all of the locations with the decline resulting in four locations having a season with no rainfall at all. Large declines in modeled net precipitation such as these would affect the overall amount of recharge to the regional aquifer. In an island ecosystem, the constant pressure of saltwater intrusion and the input of freshwater recharge creates a delicate balance of fresh and saline water underground. Any change in net precipitation that affects recharge could disrupt that delicate balance allowing increased saltwater intrusion along the coastline and within the Park.
Open Access
Procedure for measurement of surficial soil strength via bevameter
(Colorado State University. Libraries, 2020) Bindner, Joseph R., author; Scalia, Joseph, IV, advisor; Niemann, Jeffrey D., advisor; Butters, Gregory, committee member; Green, Timothy R., committee member
Spatial prediction of moisture-variable soil strength is critical for forecasting the trafficability of vehicles across terrain. The Strength of Surface Soils (STRESS) model calculates soil strength properties as a function of soil texture from SSURGO data (or locally available data) and soil moisture from the Equilibrium Moisture from Topography, Vegetation, and Soil (EMT+VS) model. The STRESS model yields soil strength properties (friction angle and moisture-variable cohesion) that vary with soil texture and moisture conditions. However, the STRESS model is hindered by a lack of surficial soil strength data linked directly to soil texture. The objective of this study is to develop and validate a bevameter procedure to improve measurement of near-surface moisture-variable soil strength. The bevameter is a test apparatus that measures in-situ surficial soil strength properties by rotational shearing of a shear annulus under a constant normal force at a constant rate. The bevameter allows for lab or field determination of Mohr-Coulomb surficial soil strength properties at a given moisture content in a manner that approximates how vehicles interact with surficial soils. Experimental variables evaluated include the shearing surface (grousers, sandpaper, or bonded angular sand) and the use of interior and exterior annular surcharge weights to minimize slip sinkage of the shear annulus. Based on the results of this study, a bevameter procedure is recommended that uses a coarse sandpaper as the shear interface with an internal and external surcharge of 2 kPa during shear testing. Using the revised bevameter procedure for field testing, the performance of predicted moisture-variable soil strength by the STRESS model is evaluated. Field validation illustrates the need to develop surficial-soil specific pedotransfer functions for use in the STRESS model.
Open Access
Quantifying groundwater recharge beneath furrow irrigated corn using lysimetry, an unsaturated zone water balance and numerical modeling
(Colorado State University. Libraries, 2013) Moubarak, Jasmeen, author; Sanford, William, advisor; Ronayne, Michael, committee member; Butters, Gregory, committee member
Understanding the effects of new irrigation methods on groundwater recharge rates in semi-arid regions is becoming more important as the demand for water in these areas increases. Predicting groundwater recharge under furrow irrigated agricultural land can be a difficult task due to spatial variability of infiltration down a furrow, as well as the heterogeneity of hydraulic properties throughout the vadose zone. There are few methods currently being used to estimate the amount of recharge under these conditions. Each method has its own set of assumptions that create varying degrees of uncertainty in the results. The objective of this study is to quantify the amount of groundwater recharge beneath various irrigation methods and to evaluate the ability of a 2D unsaturated zone model to predict these results. The study will compare the results of two field water balance methods conducted at an experimental furrow irrigated agricultural site with those obtained using a 2D unsaturated zone model. For this experiment, a 15-acre corn field was sub-divided into three blocks with one block fully irrigated and two blocks under deficit irrigation. For each block, deep percolation (DP) was estimated at two to three locations using lysimetry and the unsaturated zone water balance (UZWB) method. The HYDRUS (2D/3D) modeling software was used to create and calibrate a model that could effectively predict the quantity and timing of the drainage flux through the vadose zone. Two models were created for each site to test the effect of soil composition and layering on goodness-of-fit to the data collected during the two growing seasons. Model calibration was performed for the 2011 season and validated with the 2012 data. The layered model calibrated to the lysimeter data performed most consistently during the validation process, although the layered model calibrated to the UZWB data showed the least bias in results and the lowest average root mean squared error (14.63 cm). Overall, this study has shown that a layered model is needed to most accurately represent water flow in this scenario, and the results of UZWB method can be used to calibrate a predictive model.
Open Access
Redox-sensitive trace elements document chemical depositional environment and post-depositional oxidation of the Ediacaran Biri Formation, southern Norway
(Colorado State University. Libraries, 2014) Marolf, Nathan J., author; Hannah, Judith, advisor; Stein, Holly, committee member; Butters, Gregory, committee member
The Ediacaran Biri Formation comprises carbonate and silisiclastic facies including a ~ 70 m thick organic-rich shale facies exposed 9 km west of Biri, Norway in a steep bedrock stream channel at Djupdalsbekken. This outcrop is overlain by ~ 30 m of coarse-clasitic conglomeritic facies of the Ring Formation, deposited in the southern and western portion of the Hedmark basin as prograding subaerial and submarine delta fans. Concentrations and distributions of some redox-sensitive trace elements, specifically molybdenum and uranium, within the Biri Formation shale indicate deposition under sub-oxic to anoxic conditions. Pyrite framboid size distribution corroborates trace element evidence and suggests that sulfidic conditions existed within the sediment with a chemocline at or near the sediment-water interface. An attempt to date the Biri Formation shale by Hannah et al. (2007) found disturbed Re-Os isotope systematics from samples in the first 8 meters of the exposure, while data obtained from samples further down section were undisturbed. Here, an attempt to understand these disturbed and undisturbed sections using redox-sensitive trace element chemistry suggests the disturbed data was a result of post-depositional re-oxygenation within the upper few meters of the Biri shale. This is indicated by concentration peaks in trace element profiles that result from remobilization and subsequent re-fixation of these elements at different locations in the shale. A well constrained hypothesis constructed using uranium and molybdenum as proxies for rhenium shows that rhenium was likely remobilized after deposition of the Biri Formation and either subsequently re-deposited, or flushed out of the system. In this scenario, the post-depositional remobilization of rhenium (and most likely osmium also) resulted in disturbed Re-Os isotope systematics described by Hannah et al. (2007). Trace element geochemistry, petrographic, and δ13C and δ18O stable isotope evidence document post-depositional re-oxygenation of the Biri Formation shale. Re-oxygenation occurred either synchronous to deposition of the overlying Ring Formation or during a later event, the Caledonian orogeny (~ 440 Ma) being the most likely candidate. While the geochemical evidence does not preclude one time period or the other, disturbed Re-Os isotope systematics and resulting dates given by Hannah et al. (2007) can only be supported by re-oxygenation of the Biri Formation shale during the Caledonian orogeny.
Open Access
Road sediment production and delivery: effects of fires, traffic, and road decommissioning
(Colorado State University. Libraries, 2016) Sosa Peréz, Gabriel, author; MacDonald, Lee H., advisor; Kampf, Stephanie, committee member; Lefsky, Michael, committee member; Butters, Gregory, committee member
Unpaved roads often are a major source of sediment to streams in forested watersheds, and an increase in sediment production and delivery can adversely degrade water quality and aquatic habitat. The first part of this study quantifies the effects of wildfires on road erosion and road-stream connectivity as a function of fire severity and road segment characteristics. The data were collected along 6.8 km of an unpaved road after the High Park wildfire in Colorado. The second and third parts of this dissertation investigate how traffic and two road decommissioning treatments affect road sediment production and road-stream connectivity through the use of rainfall simulations, sediment production measurements at the road segment scale, and repeated surveys of 12.3 km of decommissioned roads. The segment-scale and road survey data were collected over a three-year period that included one summer prior to decommissioning and the first two years after decommissioning. The road-wildfire study indicated that road surface rill erosion increased with hillslope burn severity due to the increasing amounts of runoff, but the length and area of rilling also increased with road segment slope. Segments with a slope ≤5% tended to capture sediment from the hillslope. Road segment area was only important for roads in areas burned at low severity, indicating that hillslopes become a progressively less important source of runoff as burn severity decreases. All of the road segments in areas burned at moderate and high severity and 78% of the segments in areas burned at low severity were connected to the stream due to the increased runoff from upslope, the concentration of hillslope and road surface runoff to a single drainage point, and the reduced infiltration and trapping capacity of the hillslopes below the road. After wildfires land managers need to increase the frequency of drainage structures, and a more integrated modeling approach is needed to further our understanding of the complex interactions between burned hillslope and roads. The rainfall simulations showed that the infiltration capacity for the decommissioning treatment of only ripping had little effect on infiltration and significantly increased sediment yields compared to closed roads. Mulching after ripping doubled the final infiltration rate and decreased sediment yields by nearly a factor of five compared to only ripping. Eighty passes of an all-terrain vehicle on two closed roads had no effect on infiltration capacity, but increased sediment yields by a factor of three. The results at the road segment-scale showed that traffic was the dominant control on sediment production, and both decommissioning treatments greatly reduced road sediment production as nearly all of the eroded sediment was trapped in the furrows. Decommissioning reduced road-stream connectivity from 12% of the total length to only 2%, with most of the connected segments being immediately adjacent to a stream. These results can help calibrate and validate road erosion models, and guide the design of future road decommissioning treatments.
Open Access
Sediment production and delivery from hillslopes and forest roads in the southern Sierra Nevada, California
(Colorado State University. Libraries, 2011) Stafford, Allison K., author; MacDonald, Lee H., advisor; Stednick, John D., committee member; Butters, Gregory, committee member
Unpaved roads often are a major source of sediment to streams in forested watersheds, and an increase in sediment production and delivery can adversely affect the overall health of a stream. The goals of this study were to first quantify the effects of climate and soil type on hillslope and road sediment production and delivery, and then evaluate the effects of graveling, grading, and waterbar construction on road sediment production and delivery. Sediment fences were used to collect 109 fence-years of data from water years 2008 and 2009 in the more rain dominated José Basin (800-1200 m) and 193 fence-years of data in the snow dominated Kings River Experimental Watersheds (KREW) (1485-2420 m), both located in Sierra National Forest (SNF) in California. Detailed road surveys assessed road segment characteristics and road-stream connectivity. Mean hillslope sediment production in José Basin was 3.7 x 10-3 kg m-2 yr-1, which was similar to the value of 4.1 x 10-3 kg m-2 yr-1 in KREW. Native surface road segments in José Basin had a mean sediment production rate of 1.8 kg m-2 yr-1, and the estimated total sediment production from the 67 km of native surface roads is 680 metric tons per year. An estimated 30% of the native surface road length is connected to the stream network, indicating that up to 210 metric tons of sediment may be delivered to streams each year. There was no significant difference in sediment production and delivery between road segments in the highly erodible Holland soil and road segments in other soil types. Mean sediment production for the native surface road segments in the KREW watersheds was 0.13 kg m-2 yr-1, which was more than an order of magnitude lower than the mean value in José Basin, and road-stream connectivity was only 3%. There was no significant difference in sediment production from native and gravel surface road segments in José Basin due to the high variability and the gravel segments still averaged 51% bare soil. The gravel surface segments had shorter drainage features than native surface segments, but 40% of the gravel roads were connected as they tended to be closer to streams. Graveled roads in the Providence Creek watersheds produced 0.16 kg m-2 yr-1, which was only 22% as much sediment as the native surface roads, and had 11% connectivity. In José Basin grading initially decreased the mean segment length from 65 m to 41 m, but one year after grading 22% of the waterbars had failed, leading to a 15% increase in mean segment length. Graded road segments in José Basin produced eight and three times more sediment per unit area than ungraded segments in WY2008 and WY2009, respectively, and this can be attributed to extensive rilling. Sediment production rates decreased by 40-60% from the first to the second year after grading. Sediment production and delivery from forest roads can be reduced by: 1) using more than 30% gravel cover on native surface roads, 2) minimizing grading, and 3) improving the construction of waterbars to better withstand and direct overland flow.
Open Access
Spatial accumulation patterns of snow water equivalent in the southern Rocky Mountains
(Colorado State University. Libraries, 2016) Von Thaden, Benjamin C., author; Fassnacht, Steven R., advisor; Stednick, John D., committee member; Butters, Gregory, committee member
Only several point measurements may be taken within a given watershed to estimate snow water equivalent (SWE) due to cost limitations, which necessitates basin-scale estimation of SWE. Modeling often assumes consistency in the spatial distribution of SWE, which may not be correct. Identifying patterns and variability in the spatial distribution of SWE can improve snow hydrology models and result in more accurate modeling. Most previous snow distribution studies focused on small domains, less than 10 km. This study examined SWE distribution at a domain of 757 km. This study used variogram analysis for SWE data from 90 long-term SNOTEL stations to determine if a physical distance exists at which snow accumulation patterns across the southern Rocky Mountains vary abruptly. The concurrent accumulation period from SNOTEL stations were paired one-by-one until all 90 stations were compared among each other for all years on record. This comparison generated a relative accumulation slope (relative to the accumulation slope of all other 89 SNOTEL stations from the period of record) and along with physical distance between station pairs, variograms were computed using the semi-variance of the relative accumulation slopes. A physical divide (a break in high-elevation terrain) exists in the topography of the study region that runs East-West about the parallel 38°45’N. Two subset variograms were computed, one by dividing station pairs by their location relative the parallel 38°45’N into a north zone and a south zone, and the second by the pair’s land cover type, specifically evergreen, non-evergreen, or mixed. From the variogram analyses two physical distances were determined (100 and 340 km) at which snow accumulation patterns in the southern Rocky Mountains vary abruptly. There was more variance in snow accumulation south of the 38°45’N parallel, as the zone north of the 38°45’N parallel experiences storm tracks different from the storm tracks that dominate the zone south of this dividing parallel. Land cover was shown to have little effect on snow accumulation patterns. The amount of variability in individual day SWE was found to be correlated to the magnitude of the average SWE among all SNOTEL stations, such that the greater the average SWE, the larger the variability in SWE across the southern Rock Mountains.
Open Access
Swell, stiffness and strength of expansive soil-rubber (ESR) mixtures at various scales: effect of specimen and rubber particle sizes
(Colorado State University. Libraries, 2012) Heyer, Lance C., author; Carraro, J. Antonio H., advisor; Shackelford, Charles D., committee member; Butters, Gregory, committee member
Expansive soils and stockpiled scrap tires present unique constructability and environmental challenges to the Front Range of Northern Colorado, respectively. Swell, stiffness and strength parameters of expansive soil-rubber (ESR) mixtures were systematically evaluated in the laboratory under one-dimensional and axisymmetric boundary conditions. ESR mixtures tested contained highly plastic, swelling clay from the Pierre shale formation and scrap tire rubber (STR) with nominal maximum particle sizes equal to approximately 6.7 or 19.0 mm. Compaction parameters were determined using standard Proctor compaction procedures (ASTM D698). Mixtures were compacted to relative compaction levels equal to 90, 95 or 100% and water contents varying by ± 2% around the optimum water content. Rubber contents used were equal to 0, 10 or 20%. Specimen and rubber particle sizes were also studied to assess differences in mechanical behavior of 6.7- and 19.0-mm ESR mixtures tested in one-dimensional compression employing three specimen sizes (small-scale, large-scale and field-scale) and in undrained axisymmetric compression employing two specimen sizes (small-scale and large-scale). Swell-compression results indicated the swell percent and swell pressure of specimens subjected to one-dimensional compression with lateral confinement were most impacted by initial water content, followed by relative compaction and rubber content. Compressibility parameters, including the constrained and elastic moduli, are most impacted by rubber content, followed by relative compaction and initial water content. Small-scale one-dimensional specimens demonstrated a minimal increase in swelling and insignificant variations in compressibility in comparison to large-scale one-dimensional and field-scale specimens. ESR specimens subjected to axisymmetric boundary conditions exhibited volumetric swell during flushing and back pressure saturation and swelling magnitudes were similar for nominal rubber particle sizes equal to 6.7 and 19.0 mm. Normal compression line parameters, λcs and κcs, were equal to 0.10 and 0.05, and 0.11 and 0.04 for large-scale 6.7- and 19.0-mm ESR specimens, respectively. Critical state parameters, Mcs, Γcs, and λcs, were equal to 1.20, 2.23 and 0.14, and 1.04, 2.15 and 0.13 for large-scale 6.7- and 19.0-mm ESR specimens, respectively. Scalability results indicate similar swell, stiffness and strength of ESR mixtures compacted to various specimen sizes with the inclusion of either 6.7- or 19.0-mm scrap tire rubber particles. Results indicate reasonable predictions of the mechanical behavior of ESR mixtures including tire chips can be made using conventional laboratory specimen sizes and testing techniques employing similar host expansive soils and rubber contents used to create ESR mixtures including granulated rubber.
Open Access
The effects of long term drainage and restoration on soil properties of southern Rocky Mountain sedge fens
(Colorado State University. Libraries, 2012) Schimelpfenig, David W., author; Cooper, David J., advisor; Sanderson, John S., committee member; Butters, Gregory, committee member
Mountain sedge fens are unique ecosystems which require thousands of years to form, provide refuge for rare plant species, and are easily disturbed by human activity. Peatland soils are significant players in the global carbon cycle, storing 1/3 of the terrestrial carbon stock. Drained peat is a persistent source of atmospheric CO2, restoring the carbon storage function to disturbed peatlands is an increasingly important justification for peatland restoration. I measured water table dynamics and CO2 flux at three small fens (< 10 ha) in SW Colorado for one year before and one year after restoration. The fens were hydrologically restored with the installation of small check dams in ditches that had drained the sites for a century. Water tables in restored areas increased during the driest periods of the summer from -45 cm below the surface to -15 cm. We measured CO2 flux (net ecosystem exchange (NEE), ecosystem respiration (ER), and gross ecosystem photosynthesis (GEP)) bi-weekly during the two growing seasons using an infrared gas analyzer attached to a 60 x 60 x 60 cm closed chamber. Mean NEE over the two year study was lowest in the disturbed areas (-1.28 g CO2 m-2 hr-1). Mean NEE in the reference area was -1.74 g CO2 m-2 hr-1 and in the restored areas was -2.19. Mean ER was similar across treatments, ranging from 0.77 and 0.92 g CO2 m-2 hr-1. Soil samples were extracted from three fens restored during this study and 1 restored in 1990 to test the effects of long term drainage and restoration on the physical properties of peat soil including; bulk density, porosity, % organic matter (OM), residual water content, and saturated hydraulic conductivity. Disturbance has caused significant changes in the peat soil including; 25% reduction in soil OM, increased bulk density, decreased porosity, and reduced saturated hydraulic conductivity. These effects persist in peat soil 20 years after restoration. Calculated OM losses of 1.4 to 3.6 kg m-2 have resulted in an estimated loss of 14.7 to 91 tons OM from each of these fens. The hydrologic regime and CO2 storage has been successfully restored in these fens, while the peat soil bears a legacy of disturbance two decades after restoration.
Open Access
The impacts of long-term cultivation on soil degradation in the San Luis Valley, Colorado
(Colorado State University. Libraries, 2016) Daniels, Judith Marie, author; Kelly, Eugene F., advisor; Butters, Gregory, committee member; Melzer, Susan E., committee member; von Fischer, Joe, committee member
Essentially all agricultural lands globally are under pressure to meet the food demands of an additional 2 billion people over the next 20 years. All of the agroecosystems possess limitations that constrain their ability to optimize production, however, these limitations are magnified in semi-arid regions where permanent, seasonal or periodic moisture deficiency results in evaporation and transpiration rates that exceed precipitation. Traditional cultivation practices that utilize modern technology have resulted in substantial amounts of soil loss through wind and water erosion, decreased soil organic matter, reduction in soil water-holding capacity, and alterations to the microbial community composition. Cultivation also affects soil chemical processes and conditions (e.g., pH, cation exchange complexes, electric conductivity, and sodium adsorption ratio) that can lead to further soil degradation. Changes in one or more of these properties often have direct or indirect effects on the fertility of soils, which influence resiliency and soil health. While research has clearly established the most common modifications to soil systems from cultivation, further investigation is needed in semi-arid regions to identify the critical links between physical, chemical, and biological properties that regulate resiliency and soil degradation. In establishing these critical links, I evaluated the importance of parent material (basalt versus granite) in assessing the impacts on the physical, chemical, and biogeochemical soil properties as a function of cultivation, specifically sprinkler and flood irrigation. I also distinguished microbial community composition by parent material and land use and identified key soil properties that regulate changes in microbial community structure by sampling native and cultivated soils in the San Luis Valley (SLV), located in the South Central part of Colorado. The SLV is a high elevation semi-arid agroecosystem with basalt and granite substrates, that receives 177 mm of precipitation annually and the potential evapotranspiration that exceeds 1016 mm. The SLV has also has a 150-year history of irrigated agriculture practices, which add an additional 153 to 1226 mm of water during the growing season. This alters the natural climate and possibly results in some degree of land degradation. Overall, the results indicate the importance of parent material (basalt vs. granite), as a soil forming factor in assessing the impact of cultivation on soil degradation processes. The initial clay percent in the native soils was 20% for basalt and 18% for granite. The additional accumulation of clay from irrigation was slightly higher for basalt soil, (22%) and 20% for granite soils. Soils derived from basalt have greater quantities of the major cations while soils derived from granite have lower quantities and a poor nutrient status. Soils derived from basalt have greater percentage of soil organic carbon in the soil surface horizons than soils derived from granite. The uncultivated soils derived from basalt classify as saline-sodic while those derived from granite were consistently non-saline, non-sodic. As a function of irrigation, the nutrient concentrations of calcium, magnesium, sodium, potassium, chloride and sulfate were reduced in basalt soils while concentrations increased in granite. In addition, the greatest accumulation of clay and soil organic carbon occurred in granite soils with flood irrigation which resulted in similar concentrations as the basalt soils. Also, basalt soils re-classified as non-saline and non-sodic while those derived from granite remain consistently non-saline non-sodic. These results demonstrate a convergence among the basalt and granite soil properties as a function of land use. Using the ester-linked fatty acid methyl ester (EL-FAMEs), which evaluates differences among soil microbial community composition based on the condition variables of parent material (granite and basalt) and treatments (control, sprinkler, and flood). The results indicated that total microbial biomass and the stress ratios differed between basalt and granite with flood irrigation and the most variation was observed in the basalt-flooded soils. The fungi-to-bacteria ratios were the same in basalt and granite soils and both irrigation types (sprinkler and flood). Arbuscular Mycorrhizal (AM) Fungi did not differ between basalt and granite, however, the concentrations of AM fungi increased in irrigated soils, suggesting alfalfa and pasture hay grasses nurture root biomass. The correlations analysis identified pH, magnesium, sodium, potassium, chloride, and organic carbon as being the primary soil properties associated with the microbial communities in both soils and treatment types. The results from the sensitivity model for microbial communities in granite soils indicated changes in these soil properties were more pronounced pH, magnesium, sodium, potassium, chloride, and soil organic carbon in both sprinkler and flood irrigation. While the microbial communities in basalt soils were sensitive to pH and soil organic carbon in both irrigation practices; the responses were negligible compared to granite soils. Physical soil properties were not significant in determining correlations or sensitivities among the microbial communities. Overall, my data revealed the importance of communally evaluating the physical, chemical, and biological properties in determining the key properties that collectively regulate resiliency and indicate soil degradation. The key indicators in this study are soil texture, bulk density, clay, soil organic matter, sodium, chloride, sulfate, and AM Fungi microbial communities, which provide a benchmark for quantifying the magnitude and directional change of soils in cultivated systems with respect to their native counterparts. The findings revealed that long-term cultivation in the SLV has not degraded the soils according to the indices used. The parameters used this study improve the understanding of long-term irrigation impacts on agroecosystems in arid and semi-arid regions by linking the substrate properties with the soil-forming factors and irrigated water quality. This study provides the key information that can be used as a matrix by which to evaluate the impacts of climate change and a growing global population in other water-limited regions.