Browsing by Subject "Soil moisture"
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Item A numerical model to incorporate the influence of shrinkage cracks on the transient moisture movement through unsaturated soil(Texas Tech University, 1994-05) Ab Rahim, Mohd A.Most natural soil deposits develop a complex network of relatively coarse voids or macropores. In swelling soil, the macropores consist primarily of shrinkage cracks that develop when the soil is subjected to prolonged dry weather. The macropores are known to allow water to move faster and deeper into the soil profile. In addition, while migrating downward through the macropores, some of the water is absorbed by the micropores in the surrounding soil matrix. The conductivity through the macropore are several orders of magnitude larger than the conductivity of the intact matrix. The macropore conductivity is controlled by the size of the macropores, and the size of the macropores is dependent on the moisture contents within the soil mass. Both the flow through the macropores and the flow through the micropores have to be considered in the analysis of the flow through porous media which consists of both macropores and micropores. In this study, a numerical model was developed to simulate the flow within the two pore systems. The conductivity of the macropores was estimated from an empirical equation. The flow in the macropores was modeled according to a simple water balance scheme. The resulting lateral flows were then coupled into the source term in the Richards equation. Finally, the Richards equation was solved using the finite element method to give the changes in the suction due to both the input fluxes at the surface and the lateral flows from the macropores. The model was designed in such a manner that the simulation can be performed in 2-dimensions with minimum soil information. The model was also equipped with a weather data processor and weather generator. The model was calibrated with field data from two sites. The result of the calibration showed that the model can fit the field data fairly well. Furthermore, several simulation runs were performed with the numerical model for several macroporous field conditions. The results of these simulations showed that macropores play an important role in water infiltration and recharg in macroporous soil.Item A re-evaluation of the filter paper method of measuring soil suction(Texas Tech University, 1996-08) Bulut, RifatThe filter paper method is a soil suction measurement technique. Soil suction is one of the most important parameters describing the moisture condition of unsaturated soils. The measurement of soil suction is crucial for applying the theory' behind the unsaturated soils. The filter paper method is a laboratory test method, but it is inexpensive and relatively simple. It is also the only known method that covers the full range of suction. With the filter paper method, both total and matric suction can be measured. If the filter paper is allowed to absorb water through vapor flow (non-contact method), then only total suction is measured. However, if the filter paper is allowed to absorb water through fluid flow (contact method), then only matric suction is measured. In this research, the filter paper method was investigated, especially the lower (wet) part ofthe total suction calibration curve. A total suction calibration curve was constructed using sodium chloride, NaCl, salt solutions and S & S No. 589 White Ribbon filter papers. Salt solutions and filter papers were brought to equilibrium through vapor flow (total suction measurement) at isothermal conditions. Equilibrium time and temperature were two weeks and 25°C , respectively. It was found out that total suction is very sensitive below 2.5 pF and the reason for this sudden change in suction arise from double effect ofthe logarithms (i.e., natural logarithm from Kelvin's equation and base ten logarithm from pF scale) and sensitivity of filter papers to water at low suctions. Filter paper is a poorly graded material, so it has more tendency to absorb water at low suctions. Another conclusion from these experiments and literature review was that the calibration curve is highly salt solution-type dependent because every salt solution has a different chemical activity thus different osmotic potential. The filter paper method needs further investigation in regard to equilibrium time and temperature fluctuations.Item A wind tunnel investigation to examine the role of air humidity in controlling the threshold shear velocity of a surface and in controlling the mass flux of material from a surface(2013-05) Massey, Joe; Lee, Jeffrey; Zobeck, Ted M.; Perry, Gad; Bateman, MarkAeolian erosion, the wind-forced movement of soil particles, is a dominant process in arid regions. The impacts of wind-driven dust emissions are numerous and can have both localized effects and far reaching impacts. The susceptibility of a soil surface to wind erosion is gauged using the threshold friction velocity (u*t), which is related to the wind speed needed for the erosion of surface material to commence. This threshold varies for every surface and depends on numerous variables, including surface soil moisture. In arid regions, which contain air-dry soils, soil moisture is the driving factor controlling changes in the threshold shear velocity of a surface at short, diurnal timescales (Ravi and D’Odorico, 2005). Therefore, an understanding of these varying moisture conditions, and the associated changes in soil erodibility, is vital in understanding and modeling aeolian soil erosion (Ravi et al., 2006). In such regions, where rainless periods are common and there is a lack of moisture provided by precipitation or capillary rise, the humidity of the overlying air is particularly influential in controlling soil moisture content at the surface (Ravi and D’Odorico, 2005). Through wind tunnel tests, this study analysed the control relative humidity had on the threshold shear velocity for three soils: a loamy fine sand, a clay loam and a sandy muck. The loamy fine sand and the clay loam material were previously studied and the results found here agreed with those from other studies (e.g., Ravi et al., 2006). The relationship found is made up of a high and low section of humidity, where the threshold shear velocity increases with humidity, and a mid-range section of humidity, where the threshold shear velocity decreases with increased humidity. The previously unstudied sandy muck also showed this relationship. The results were explained using the theory of equilibrium between the surface soil moisture and the humidity of the overlying atmosphere. In such studies, an accurate measurement of the threshold shear velocity is vital and this study compared the sensitivity of two particles sensors (Wenglor YH03PCT8 and Sensit model H10) in determining the threshold shear velocity of a soil surface. It was found that the newer Wenglor sensor recorded the threshold at considerably lower wind speeds throughout the test and for each soil. This, however, did not significantly change the relationship seen between the threshold shear velocity and relative humidity. For the first time, this study aimed to investigate the effect humidity has on the erodibility of a surface over a sustained period of time. This was done by analysing the mass flux of PM10 from each soil at a range of humidities. It was found that the initial threshold shear velocity of the surface had no control over the average mass flux of material from the surface. For the clay loam and sandy muck, the humidity also had no control over the average mass flux of material from the surface. The loamy fine sand, however, exhibited a strong, linear relationship between the humidity and the total mass removed. This was explained using a theory suggesting that the higher percentage of larger grains in this soil preferentially absorbed water from the atmosphere when compared to smaller grains, meaning smaller grains are less affected by the threshold. Finally, this study analysed the control of humidity on the time it takes for mass flux to reach its peak value. It was found that the threshold shear velocity had a substantial control over the time to mass flux. This showed that the overlying humidity of the air only affected the grains at the surface (≈top 2mm) and, under prolonged wind erosion, the initial threshold of the surface was no longer apparent at the surface and a new threshold was developed.Item An investigation of the thermal conductivity of a sandy soil as a function of soil moisture content(Texas Tech University, 1986-05) Gupta, SunilEnergy consumption for heating and cooling of residential and non-residential buildings is a significant portion of the total amount of energy used in the United States. Space heating and cooling accounts for almost 25 percent of the total U.S. consumption (as much as is consumed by all of transportation) and the potential for savings is very large indeed (5). For the residential sector alone, space heating accounts for 65 percent of all residential energy with a further 5 percent for space cooling (5). Space heating and cooling is by far the largest component of energy use in this sector, and this alone accounts for almost 16 percent of the nation's total raw energy use and is supplied primarily by natural gas and petroleum products (5).Item At-risk wastewater pipeline identification due to flooding(2016-05) Abbott, Kristin Whitley; Faust, Kasey M.; King, Carey Wayne, 1974-; Kreitler, CharlesCorrosion is a risk to all ferrous pipelines, and the impact of moisture from major flood events in potentially corrosive soils upon the corrosion of sensitive pipeline materials has not yet been thoroughly studied. Rapidly accelerated corrosion from flooding can cause a pipeline break and lead to environmental hazards. This research seeks to quantify the risk of wastewater pipeline components to fracturing and damage from flooding to inform decision-makers. The corrosion risk to Austin Water Utility’s aged ferrous wastewater pipelines from surrounding soil through flooding is analyzed by establishing the relationships among pipeline material, age, and the surrounding soil type. First, aged ferrous wastewater pipelines in the network were isolated. Then, the Web Soil Survey from the United States Geological Survey (USGS) for Travis County and FEMA Flood Insurance Rate Maps (FIRM) were overlaid on the selected pipelines. USGS soil data was used to locate potentially corrosive soils surrounding the pipelines. Third, FIRM flood zones were overlaid on the selected soil and pipelines in order to examine the relationship between soil type, moisture, and increased corrosion potential. Three different flood zones were evaluated. The analysis shows a total of 386 pipelines, or 27.99 miles of pipelines, were identified to be at-risk.Item Characterization of drought in Texas using NLDAS soil moisture data(2013-05) Sullivan, John R., Jr.; Maidment, David R.From June to August 2011, Texas experienced the hottest summer ever recorded in the history of the United States, and the state suffered a water shortage that made its vulnerability to drought painfully plain. This disaster sparked new interest in methods of defining drought severity, especially with regard to the variation of soil moisture levels. This thesis assesses the suitability of information from the North American Land Data Assimilation System (NLDAS), an assemblage of land surface models forced with observations data, for quantifying soil moisture levels in Texas. The potential for combining NLDAS data with the Soil Survey Geographic (SSURGO) Database’s available water capacity data is explored. It is discovered that because NLDAS is a hydrological model and SSURGO an agricultural dataset, they employ different definitions of soil moisture storage. Moreover, the temporal variation of soil moisture levels in the SSURGO polygons cannot be inferred from NLDAS data due to the vastly different spatial scales of the two datasets. A relative measure of soil saturation from 0–100% is developed instead and determined to be a more useful indicator of drought than the soil moisture level itself. Calculated solely from NLDAS data, it is used to map the severity of drought in Texas, with the results displayed at the county scale. The temporal variation in soil moisture storage across the state is compared with variations in the gravity anomaly measured by NASA’s Gravity Recovery and Climate Experiment (GRACE) satellites and variations in Texas surface water reservoir levels, both of which are physical measurements of water storage changes. This analysis suggests that the NLDAS data, which is derived from a land surface model, accurately describes subsurface moisture variations. Also, the GRACE gravity anomaly data reveals that during the 2011 drought, the total water storage in Texas was approximately 100 cubic kilometers less than normal. NLDAS data indicates that more than 50% of this deficit was due to losses from the top one meter of the state’s soils.Item Effects of altered precipitation regimes on North American desert plant physiology(Texas Tech University, 2008-05) Patrick, Lisa Dori; Tissue, David T.; Holaday, A. Scott; Loik, Michael; Payton, Paxton R.; Zak, JohnClimate change will significantly impact deserts since precipitation drives biological activity in these ecosystems. Further, ecosystem responses to precipitation may be non-linear due to differential species responses to variation in the timing and magnitude of precipitation. Since plants impact total ecosystem function, it is critical to evaluate physiological responses to precipitation across multiple spatial and temporal scales. As such, this dissertation focuses on the physiological responses of desert grasses and shrubs to altered precipitation, spanning from the leaf- to the ecosystem-level. First, I examined the effects of increased precipitation on ecosystem fluxes of CO2 and H2O in Big Bend National Park (BIBE), Texas in the Chihuahuan Desert. To partition ecosystem fluxes, I conducted field measurements of plant, soil, and ecosystem fluxes after precipitation pulses throughout the summer. Increased summer precipitation altered soil carbon and water, and plant water fluxes over shorter time scales and carbon fluxes of grasses over longer time scales, which may lead to increased ecosystem carbon storage. Second, I focused on the leaf-level by measuring short-term physiological responses to precipitation events. I collected photosynthesis data for dominant plants in BIBE to examine the effects of natural and supplemental seasonal precipitation on carbon fluxes. I also measured environmental and biological variables to determine regulators of photosynthesis. Leaf-level fluxes of shrubs were more sensitive to both the amount of deep soil water and nitrogen, while grasses were only affected by leaf nitrogen. Further, increased precipitation in the summer and winter could have significant impacts on plant carbon gain and utilization due to soil nitrogen dynamics. Lastly, I collected photosynthetic data for seven dominant desert plants across North America to determine if the responses seen in BIBE were common across all deserts. I developed a Bayesian model of photosynthesis to analyze these data. Photosynthetic responses were similar across deserts and species, but different from temperate forest trees, leading to a unified understanding of desert plant physiology. When photosynthesis parameters were examined in relation to altered precipitation, data indicated that increased summer precipitation altered maximum electron transport and the temperature sensitivity of enzymatic reactions in C3 shrubs. Altered seasonal precipitation regimes also decoupled relationships between limitations to photosynthesis and nitrogen across all deserts and species studied.Item Effects of particle-size distribution, organic matter and calcium carbonate on water retention of Texas High Plains soils(Texas Tech University, 1985-05) Meng, Tan PiowThe overall objective of the research program was to provide data that will allow the prediction of the probable effectiveness of precipitation when deep plowing has altered the texture of the plow layer.Item Evaluation of soil water quality following the application of biosolids on a semiarid rangeland in Texas(Texas Tech University, 1995-05) Brenton, Cynthia MarieBiosolids are the by-product of wastewater treatment plants and it is estimated that six million metric tons of biosolids are produced annually in the United States. Biosolids contain large amounts of phosphorus and nitrogen as well as heavy metals and inorganic compounds. The amount of heavy metals and other constituents in the biosolids depends on the source and treatment process of the sewage sludge. At Sierra Blanca Ranch, Texas, biosolids are being applied at a rate of 6.6 dry Mg/ha to rangeland as a reclamation project. Aside from studies on the effects of sewage sludge on vegetation growth, it is also important to study the effects sludge has on soil water quality. In this study, two contrasting soil types on the ranch were chosen: a finer textured soil (Stellar loam) and a coarser textured soil (Armesa taxajunct fine sandy loam). Twenty-five 25.4 cm diameter, tube lysimeters were inserted into each of the soil types and a soil column was extracted. Five treatment rates of 0 (the control), 6.6, 17.6, 34 and 90 dry Mg/ha were randomly applied to the lysimeters with 5 repetitions. Water (simulated rainfall) was applied to each lysimeter to produce 1 liter of soil water leachate for analysis. Leachate was analyzed for 24 metals and other constituents such as sulfate, nitrate nitrogen, pH, ortho-phosphate, calcium hardness, total hardness and chlorides. All processes of simulated rainfall, leachate collection and analysis were conducted initially on freshly applied biosolids and 60-110 days later after the biosolids had aged. Results show that of 31 ANOVA tests preformed on the first leaching of the Stellar loam soil, 17 tests showed statistically significant differences in leachate among treatment rates. In the second leaching of the loam soil, 5 tests showed statistically significant differences among treatment rates. Nitrate nitrogen, pH, sulfate, and ortho-phosphate were significant in both sampling periods. Results from the Armesa taxajunct fine sandy loam were very different from the loam. The first leaching date had only 2 elements (Zn and Ba) that showed statistically significant differences among treatment rates. On the second leaching date, only Mg showed a statistical difference among the 5 treatments. For the commercial application rate (6.6 dry Mg/ha), heavy metals and nitrate nitrogen levels in the soil water leachate from both soils were found to be within guidelines set by the United States Environmental Protection Agency (USEPA) for drinking water on both sampling dates. In general, the leachate quality was statistically unaffected by 0, 6.6 and 17.6 dry Mg/ha rates and only began to show an increase with the 34 dry Mg/ha rate and the 90 dry Mg/ha rate. In some cases, even the 90 dry Mg/ha rate proved to be within drinking water quality standards on many of the metals and inorganic compounds. Finally, during a normal rainfall season, the leachate would not be expected to reach the groundwater table on the Ranch, which is in excess of 152.4 m. Total infiltration of the equivalent of 8.2 cm of precipitation over 24 hours was required to move water through 74.8 cm of the coarser Armesa taxajunct fine sandy loam soil.Item Fungal functional diversity: exploring patterns and processes associated with soil fungal assemblages along an altitudinal gradient in the Chihuahuan Desert(Texas Tech University, 2002-05) Sobek, Edward AndrewSoil fungi are intimately associated with the maintenance and stability of terrestrial ecosystems through their involvement in the decomposition process. During decomposition, organic carbon is mineralized to CO2 and bound nutrients are returned to the labile soil nutrient pool for subsequent growth of plants and soil microbes. To better understand the relationship between soil fungal diversity, and factors influencing their functional ability in the decomposition of soil organic matter, this dissertation examined, (1) development of methods to determine soil fungal functional diversity, (2) seasonal trends in fungal function al diversity, and (3) the relation between soil fungal functional abilities and a suite of environmental variables that are important in ecosystem nutrient cycles. The context of this research endeavor focused on assemblages of soil fungi associated with an environmental gradient in the Chihuahuan Desert, specifically, the Pine Canyon Watershed in Big Bend National Park. The Pine Canyon Watershed contains five distinct vegetation zones along an altitudinal gradient and contains the majority of vegetation types that are found in the Chihuahuan Desert. Soil samples were collected within each of these zones over a three-year period. Sampling coincided with seasonal changes in temperature and precipitation. Functional diversity was determined for fungal assemblages from each vegetation zone, using the Soil FungiLog procedure developed from this research.Item Influence of soil separates and mineralogy on soil-water content as affected by super slurper(Texas Tech University, 1982-12) Layla, Souhail TNot availableItem Investigation of Soil Moisture - Vegetation Interactions in Oklahoma(2013-03-06) Ford, Trenton W.and-atmosphere interactions are an important component of climate, especially in semi-arid regions such as the Southern Great Plains. Interactions between soil moisture and vegetation modulate land-atmosphere coupling and thus represent a crucial, but not well understood climate factor. This study examines soil moisture-vegetation health interactions using both in situ observations and land surface model simulations. For the observational study, soil moisture is taken from 20 in situ Oklahoma Mesonet soil moisture observation sites, and vegetation health is represented by MODIS-derived normalized difference vegetation index (NDVI). For the modeling study, the variable infiltration capacity (VIC) hydrologic model is employed with two different vegetation parameterizations. The first is the model default vegetation parameter which is interannually-invariant leaf area index (LAI). This parameter is referred to as the control parameter. The second is MODIS-derived LAI, which captures interannual differences in vegetation health. Soil moisture simulations from both vegetation parameterizations are compared and the VIC-simulated soil moisture?s sensitivity to the vegetation parameters is also examined. Correlation results from the observation study suggest that soil moisture-vegetation interactions in Oklahoma are inconsistent, varying both in space and time. The modeling results show that using a vegetation parameterization that does not capture interannual vegetation health variability could potentially result in dry or wet biased soil moisture simulations.Item Investigation of temporal variations in electromagnetic properties of soil(Texas Tech University, 2001-08) Gribenko, Alexander V.The purpose of this study was to determine if non-invasive electromagnetic methods could be calibrated to detect soil moisture variations in a field. Several electromagnetic methods were applied that are sensitive to a broad range of subsurface properties. By using several different geophysical tools we could determine which properties affect each method the most, and we could determine what properties of the soil were most affected by small changes in physical condition (e.g., water content, temperature, plant growth, etc.). We wanted to determine the most sensitive and cost effective methods to detect short-term changes in electromagnetic properties and therefore soil moisture. Before proceeding with the local survey that would be most sensitive to temporal variations in soil conditions we conducted a regional survey about the localized study area to determine if anomalous behavior would be of concern, and to have a better understanding of the study site. The regional survey was accomplished using an EM-34 electromagnetic device. We therefore wrote a program to invert these data for changes in soil properties. Detailed lithological data was available in this region, which was used to constrain the inversion of the EM34 data.Item Mapping in-field cotton fiber quality and relating it to soil moisture(2009-05-15) Ge, YufengThe overarching goal of this dissertation project was to address several fundamental aspects of applying site-specific crop management for fiber quality in cotton production. A two-year (2005 and 2006) field study was conducted at the IMPACT Center, a portion of the Texas A&M Research farm near College Station, Texas, to explore the spatial variability of cotton fiber quality and quantify its relationship with in-season soil moisture content. Cotton samples and in-situ soil moisture measurements were taken from the sampling locations in both irrigated and dry areas. It was found that generally low variability (CV < 10%) existed for all of the HVI (High Volume Instrument) fiber parameters under investigation. However, an appreciable level of spatial dependence among fiber parameters was discovered. Contour maps for individual fiber parameters in 2006 exhibited a similar spatial pattern to the soil electrical conductivity map. Significant correlations (highest r = 0.85) were found between most fiber parameters (except for micronaire) and in-season soil moisture in the irrigated areas in 2005 and in the dry area in 2006. In both situations, soil moisture late in the season showed higher correlation with fiber parameters than that in the early-season. While this relationship did not hold for micronaire, a non-linear relationship was apparent for micronaire in 2006. This can be attributed to the boll retention pattern of cotton plants at different soil moisture levels. In addition, a prototype wireless- and GPS-based system was fabricated and developed for automated module-level fiber quality mapping. The system is composed of several subsystems distributed among harvest vehicles, and the main components of the system include a GPS receiver, wireless transceivers, and microcontrollers. Software was developed in C language to achieve GPS signal receiving, wireless communication, and other auxiliary functions. The system was capable of delineating the geographic boundary of each harvested basket and tracking it from the harvester basket to the boll buggy and the module builder. When fiber quality data are available at gins or classing offices, they can be associated with those geographic boundaries to realize fiber quality mapping. Field tests indicated that the prototype system performed as designed. The resultant fiber quality maps can be used to readily differentiate some HVI fiber parameters (micronaire, color, and loan value) at the module level, indicating the competence of the system for fiber quality mapping and its potential for site-specific fiber quality management. Future improvements needed to make system suitable for a full-scale farming operation are suggested.Item Plant and soil water relationships following sand shin oak control(Texas Tech University, 1983-05) Galbraith, John MichaelStudies of soil water use by forage and competitive deep-rooted brush species are needed to make brush management decisions in the seiaiarid southwestern United States. A study was conducted on a sandy soil in west Texas supporting a dense stand of sand shin oak (Quercus havardii) and an adjacent area treated with tebuthiuron in 1978 to control the shin oak. Root and rhizome distributions were estimated by auger extraction and washing, and forage yield was estimated by clipping. Both total and available soil water, water use, and water use efficiency were estimated by neutron scattering in 1981 and 1982. Measurable soil water savings began at the first herbicide-induced resprouting cycle of shin oak. Available water tended to be higher in the grass-forb community which remained after herbicide removal of the shin oak than in the shin oak-grass community. Water use efficiency was higher in shin oak-grass vegetation than in the grass-forb vegetation. Clipping, or simulated grazing, had minimal effect on water use efficiency of vegetation in the grass-forb community. Although sand shin oak efficiently uses water, the water used could be used by more desirable vegetation. Shin oak has a deeper effective rooting depth than most associated herbaceous plants. The grasses and forbs remaining after shin oak control extended their effective rooting depths to take advantage of additional available water. Soil water potentials were higher below 137 cm (effective rooting depth of herbaceous plants) in the herbicide- treated area than in the untreated area. Shin oak developed and maintained more negative midday leaf water potentials than associated plants (-25 to -30 bars). Most plants had more negative midday leaf water potentials in shin oak areas than in herbicidetreated areas because less soil water was available to them. Shin oak is the dominant plant on sandy soils within its range because of its morphological and physiological adaptations. To simulate short-duration grazing, or when the oak-grass vegetation was compared to shin oak alone after all understory species had been removed by hand. Therefore, sand shin oak can be considered an efficient user of rainfall for aboveground biomass production in its native environment in west Texas.Item Relation of soil moisture to growth responses in apple trees(Texas Tech University, 1941-05) Elle, George ONot availableItem Soil moisture modeling and scaling using passive microwave remote sensing(Texas A&M University, 2007-04-25) Das, Narendra N.Soil moisture in the shallow subsurface is a primary hydrologic state governing land-atmosphere interaction at various scales. The primary objectives of this study are to model soil moisture in the root zone in a distributed manner and determine scaling properties of surface soil moisture using passive microwave remote sensing. The study was divided into two parts. For the first study, a root zone soil moisture assessment tool (SMAT) was developed in the ArcGIS platform by fully integrating a one-dimensional vadose zone hydrology model (HYDRUS-ET) with an ensemble Kalman filter (EnKF) data assimilation capability. The tool was tested with dataset from the Southern Great Plain 1997 (SGP97) hydrology remote sensing experiment. Results demonstrated that SMAT displayed a reasonable capability to generate soil moisture distribution at the desired resolution at various depths of the root zone in Little Washita watershed during the SGP97 hydrology remote sensing experiment. To improve the model performance, several outstanding issues need to be addressed in the future by: including "effective" hydraulic parameters across spatial scales; implementing subsurface soil properties data bases using direct and indirect methods; incorporating appropriate hydrologic processes across spatial scales; accounting uncertainties in forcing data; and preserving interactions for spatially correlated pixels. The second study focused on spatial scaling properties of the Polarimetric Scanning Radiometer (PSR)-based remotely sensed surface soil moisture fields in a region with high row crop agriculture. A wavelet based multi-resolution technique was used to decompose the soil moisture fields into larger-scale average soil moisture fields and fluctuations in horizontal, diagonal and vertical directions at various resolutions. The specific objective was to relate soil moisture variability at the scale of the PSR footprint (800 m X 800 m) to larger scale average soil moisture field variability. We also investigated the scaling characteristics of fluctuation fields among various resolutions. The spatial structure of soil moisture exhibited linearity in the log-log dependency of the variance versus scale-factor, up to a scale factor of -2.6 (6100 m X 6100 m) irrespective of wet and dry conditions, whereas dry fields reflect nonlinear (multi-scaling) behavior at larger scale-factors.Item Item Water movement in selected Texas High Plains soils(Texas Tech University, 1972-05) Paetzold, R. FNot availableItem Water Relationships of Honey Mesquite (Prosopis Glandulosa Torr. Var. Glandulosa)(Texas Tech University, 1973-05) Easter, Sammy JoeNot Available.