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DisciplineGraduate College (195)

Hydrology and Water Resources (195)

AuthorsNeuman, Shlomo P. (28)Ince, Simon (26)Evans, Daniel D. (25)Sorooshian, Soroosh (25)Simpson, Eugene S. (23)Davis, Donald R. (20)Harshbarger, John W. (19)Warrick, Arthur W. (17)Davis, Stanley N. (14)Maddock, Thomas (14)View MoreTypes
Dissertation-Reproduction (electronic) (195)

text (195)SubjectsAcid deposition -- Sierra Nevada (Calif. and Nev.) -- Mathematical models. (1)Acid mine drainage -- Environmental aspects -- Arizona -- Pinal Creek Watershed. (1)Agriculture, Plant Culture. (1)Agriculture, Soil Science. (4)Alluvial fans -- Mathematical models. (1)View More
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Stochastic analysis of high-permeability paths in the subsurface

Silliman, Stephen Edward Joseph (The University of Arizona., 1986)

Subsurface fluids may travel along paths having a minimum permeabilility greater than the effective permeability of the rock. This may have an important impact on contaminant migration. A stochastic approach related to percolation theory is advanced to address the question of what is the probability that a high permeability path extends across a given volume of the subsurface. The answer is sought numerically through subdividing the volume of interest into a three-dimensional grid of elements and assigning a random permeability to each element. Four permeability processes are considered: 1) Stationary with independence between grid elements; 2) Stationary and autocorrelated; 3) Nonstationary due to conditioning on measured values; and 4) Random rock volume included in grid. The results utilizing data from fractured granites suggest that in large grids, at least one path having a minimum permeability in excess of the "effective" rock permeability will cross the grid. Inclusion of autocorrelation causes an increase in the expected value of the minimum permeability of such a path. It also results in a significantly increased variance of this permeability. Conditioning on field permeabilities reduces the variance of this value over that obtained by unconditional, correlated simulation, but still produces a variance greater than that obtained when independence was assumed. When conditioning is performed, the mean of the minimum permeabilities along these paths is dependent on the principal axis of the path. Finally, including a random rock volume by allowing the length of the grid to be random increases the variance of the minimum permeability.

Applications of Box-Jenkins methods of time series analysis to the reconstruction of drought from tree rings

Meko, David Michael. (The University of Arizona., 1981)

The lagged responses of tree-ring indices to annual climatic or hydrologic series are examined in this study. The objectives are to develop methods to analyze the lagged responses of individual tree-ring indices, and to improve upon conventional methods of adjusting for the lag in response in regression models to reconstruct annual climatic or hydrologic series. The proposed methods are described and applied to test data from Oregon and Southern California. Transfer-function modeling is used to estimate the dependence of the current ring on past years' climate and to select negative lags for reconstruction models. A linear system is assumed; the input is an annual climatic variable, and the output is a tree-ring index. The estimated impulse response function weights the importance of past and current years' climate on the current year's ring. The identified transfer function model indicates how many past years' rings are necessary to account for the effects of past years' climate. Autoregressive-moving-average (ARMA) modeling is used to screen out climatically insensitive tree-ring indices, and to estimate the lag in response to climate unmasked from the effects of autocorrelation in the tree-ring and climatic series. The climatic and tree-ring series are each prewhitened by ARMA models, and crosscorrelation between the ARMA residuals are estimated. The absence of significant crosscorrelations Implies low sensitivity. Significant crosscorrelations at lags other than zero indicate lag in response. This analysis can also aid in selecting positive lags for reconstruction models. An alternative reconstruction method that makes use of the ARMA residuals is also proposed. The basic concept is that random (uncorrelated in time) shocks of climate induce annual random shocks of tree growth, with autocorrelation in the tree-ring index resulting from inertia in the system. The steps in the method are (1) fit ARMA models to the tree-ring index and the climatic variable, (2) regress the ARMA residuals of the climatic variable on the ARMA residuals of the treering index, (3) substitute the long-term prewhitened tree-ring index into the regression equation to reconstruct the prewhitened climatic variable, and (4) build autocorrelation back into the reconstruction with the ARMA model originally fit to the climatic variable. The trial applications on test data from Oregon and Southern California showed that the lagged response of tree rings to climate varies greatly from site to site. Sensitive tree-ring series commonly depend significantly only on one past year's climate (regional rainfall index). Other series depend on three or more past years' climate. Comparison of reconstructions by conventional lagging of predictors with reconstructions by the random-shock method indicate that while the lagged models may reconstruct the amplitude of severe, long-lasting droughts better than the random-shock model, the random-shock model generally has a flatter frequency response. The random-shock model may therefore be more appropriate where the persistence structure is of prime interest. For the most sensitive series with small lag in response, the choice of reconstruction method makes little difference in properties of the reconstruction. The greatest divergence is for series whose impulse response weights from the transfer function analysis do not die off rapidly with time.

Simulation of stream pollution under stochastic loading

Nnaji, Soronadi. (The University of Arizona., 1981)

A risk-based approach for addressing several non-structural stream quality management objectives is presented. To estimate risk, the input process, the stream contaminant transport, and the consequence of contamination are modeled mathematically. The transport of soluble contaminant introduced at a point into a turbulent stream medium is modeled as a boundary value problem in which the contaminant satisfies the Kolmogorov forward equation within the medium. Observed properties of turbulence are used to justify the adoption of this equation. The fundamental solution, as the probabilistic response of the stream to an instantaneous unit flux input, is derived and used as the kernel in a stochastic integral representation of the transport problem. The bulk input is used as the forcing function in the integral equation. It is modeled as a sequence of independent pulses with random magnitude and duration and also with random interval between the incidence of adjacent pulses ,. Stochastic simulation is used to construct the moments and the probability distribution of stream concentration and those of several variables associated with the exceedance of the concentration above a specified threshold. The variables include the dosage and the time to the first exceedance. The probability that an observed stream concentration exceeds the threshold within a given interval of time is also constructed. Generalizations of the Chebyshev inequality are extended to the case of a stochastic process. Upper bounds on the constructed probability distributions are calculated using these extensions. Based on previous studies, a rectangular hyperbolic relationship is assumed between dosage and consequence. The relationship is combined with the empirical dosage density function to obtain estimates of value risk of stream concentration for various thresholds. Given an acceptable risk, the corresponding threshold may be used as the stream standard. The reliability function, defined as the complementary density function of exceedance times, may be used as a gauge of the effectiveness of pollution abatement measures. Other illustrated areas of application include the construction of a minimum cost contaminant discharge policy and the determination of the optimal sampling interval for stream surveillance.

Analysis of factors controlling groundwater flow for prediction of rates of groundwater movement and changes in quality, Atlantic coastal plains.

Ganus, William Joseph,1936- (The University of Arizona., 1972)

The development of an open pit phosphate mine in 1965 near Aurora, North Carolina, required groundwater withdrawals in excess of 50 million gallons per day for pressure relief from the underlying confined Castle Hayne aquifer. The effects of pumping from this limestone aquifer were widespread, extending over an area of more than 2,000 square miles in the first year before the pressure cone reached a stabilized condition. Salt water encroachment by lateral movement from downdip in the aquifer and by downward leakage from the Pamlico Estuary and Sound was possible if prolonged pumping were permitted. A joint project between state and industry in 1970-71 focused on analyzing the effects of five years of pumping for the purpose of making projections of future conditions of groundwater quality for continued and expanded groundwater development. The present study describes the method of flow net analysis used in the joint project to determine quantitatively the values of aquitard vertical permeability and aquifer transmissivity. These values provided the rational basis for making projections of groundwater movement and quality changes associated with this movement, A hydrologic projection model, developed in the present study, integrates the quality and volumetric flow of vertical leakage with that of lateral flow. Projection analyses are presented for two hypothetical cases of chloride distribution changed by continued pumping and for chloride changes associated with three different pumping regimes in the subject area.

IN SITU MEASUREMENT OF GAS DIFFUSION CHARACTERISTICS IN UNSATURATED POROUS MEDIA BY MEANS OF TRACER EXPERIMENTS.

KREAMER, DAVID KENNETH. (The University of Arizona., 1982)

A gas-diffusion tracer experiment was conducted at the ChemNuclear, Inc., nuclear waste burial site near Barnwell, South Carolina, on June 1-10; 1981, testing a new methodology to measure the in situ gaseous diffusion characteristics of unsaturated porous media for the purpose of estimating the diffusive flux of volatile contaminants from the burial ground. The tracers used were CClBrF₂ and SF₆. They were released in the subsurface from permeation devices that closely approximate an ideal point-diffusion source. The permeation devices contain the tracer in liquid form and allow the tracer to escape at a constant rate by diffusion through a Teflon membrane. The release rates for CClBrF₂ and SF6 during the test were 105 and 3.3 nanograms/second, respectively. These compounds were selected on the basis of their compatabi1ity with the permeation-release device, their absence in the subsurface, and detectability in the part-per-tri11ion range in soil gas. Analyses were made in the field on a Varian 3700 series gas chromatograph equipped with an electron-capture detector. The instrument was modified to introduce soil gas through sampling valves and a Nafion tube desiccant. The diffusion sources were placed in the unsaturated soil at depths of 2 meters and 13 meters below land surface. Diffusive movements of tracer were monitored for a period of 7 days and tracer breakthrough was observed at points up to 3.5 meters away. Diffusion was modeled using a three-dimensional, continuous point source, transient-state, analytical model which allowed estimation of the effective diffusion coefficient of the porous media, and an independent assessment of the media's sorptive effects on the tracer gas. The model was calibrated using least squares and curve matching techniques, the latter of which enables a field technician to quickly interpret observed field data. Field values obtained for effective diffusion coefficient ranged from 0.026 to 0.037 cm²/sec. The average tortuosity factor observed for test site was 0.705.

Improving efficiency and effectiveness of Bayesian recursive parameter estimation for hydrologic models

Misirli Baysal, Feyzan (The University of Arizona., 2003)

There are several sources of uncertainties in hydrologic modeling studies. Conventional deterministic modeling techniques typically ignore most of these uncertainties. However, there has been a growing need for better quantification of the accuracy and precision of hydrologic model predictions. Bayesian Recursive Estimation (BaRE) is an algorithm being developed towards considering these uncertainties for parameter estimation and prediction within an operational setting. This dissertation work evaluated and improved the current version of the algorithm. The methodology was improved using a progressive re-sampling of the Highest Probability Density (HPD) region of the parameter space, which concentrated the samples in the current HPD region while terminating computations in the nonproductive portions of the parameter space, rather than evaluating feasible parameter space based on the initial set of samples. The covariance structure of the well behaving parameter sets is used to generate new parameter sets, resulting in significant improvements compared to the original BaRE. Further, to reduce the "model/data overconfidence" problem, an entropy term and a data lack-of-confidence factor were introduced into the probability-updating rule. Comparison to batch calibration using the popular Shuffled Complex Evolution (SCE-UA) optimization method indicated that the improved recursive calibration technique is a powerful tool, especially useful where basins are recently gauged and hydrologic data are not well accumulated. The final method is also effective in tracing the temporal variations of parameters as a response to natural or human induced changes in the hydrologic system.

Assimilation of satellite-derived cloud cover into the Regional Atmospheric Model System (RAMS) and its impacts on modeled surface fields

Yucel, Ismail (The University of Arizona., 2001)

The goal of this study is to provide an improved, high resolution, regional diagnosis of three important surface variables on the land surface energy and water balance, namely the downward short-wave and downward long-wave surface radiation fluxes, and precipitation. Cloud cover is a key parameter linking and controlling these three terms. An automatic procedure was developed to derive high-resolution (4 km x 4 km) fields of fractional cloud cover from visible band, (GOES series) geostationary satellite data using a novel tracking procedure to determine the clear-sky composite image. In our initial data assimilation studies, the surface short-wave radiation fluxes calculated by RAMS were simply replaced by the equivalent estimated values obtained by applying this high-resolution satellite-derived cloud cover in the UMD GEWEX/SRB model. However, this initial study revealed problems associated with inconsistencies between the revised solar radiation fields and the RAMS-calculated incoming long-wave radiation and precipitation fields, because modeled cloud cover remained unchanged and, consequently, these other surface fields retained their low, clear-sky values. It was recognized that the UMD GEWEX/SRB model provides an important relationship between cloud albedo, cloud optical depth and cloud water/ice. Thus, exploration was made of feasibility of directly assimilating vertically integrated cloud water/ice fields to update modeled cloud cover. This approach will not only enhance the realism of radiation scheme in RAMS, but it may also dramatically increase the model's capability to predict the location of precipitation, thus enhancing the ability of such mesoscale modeling systems to make accurate short-term forecasts of precipitation. This, in turn, would benefit flood forecasting as an associate hydrologic response. In the method adopted, the assimilated image takes the horizontal distribution of cloud from the satellite image but it retains a vertical distribution which is the area-average simulated by RAMS across the modeled domain in the time step immediately prior to cloud assimilation. Cloud assimilation is made every minute, with linear interpolation applied to derive cloud images for each minute between two GOES samples. Comparisons were made between modeled and observed data taken from the AZMET weather station network for model runs with and without cloud assimilation to demonstrate the improvement in RAMS' ability to describe surface radiation and precipitation fields. Cloud assimilation was found to substantially improve the RAMS model's ability to capture both the temporal and spatial variations in surface fields associated with observed cloud cover. The sensitivity of these comparisons to model initiation was explored by making five ensemble runs starting from different initiation. In general, RAMS with cloud assimilation technique is not sensitive to realistic perturbation of initial conditions.

Single- and cross-hole pneumatic injection tests in unsaturated fractured tuffs at the Apache Leap Research Site near Superior, Arizona

Illman, Walter A. (The University of Arizona., 1999)

This dissertation documents research results from a series of field experiments and analyses used to test interpretive models for investigating the role of fractures in fluid flow through unsaturated, fractured tuffs. It summarizes the experimental design of single- and cross-hole pneumatic injection tests, including borehole configuration and testing schedules, data collection system, interpretive models developed and tested, data, and conclusions. Single-hole tests were interpreted by Guzman et al. (1996) by means of steady-state analysis to obtain permeability values based solely on late pressure data. This dissertation and Illman et al. (1998) employ pressure and pressure-derivative type-curves to analyze transient data. Air permeabilities determined from transient analyses agree well with those derived from steady-state analyses. Cross-hole pneumatic tests were analyzed by means of a graphical matching procedure using newly-developed pressure and pressure-derivative type-curves. Analyses of pressure data from individual monitoring intervals using these new type-curves, under the assumption that the rock acts as a uniform and isotropic fractured porous continuum, yield results that are comparable with parameters obtained from a numerical inverse procedure described in Illman et al. (1998). The results include information about pneumatic connections between the injection and monitoring intervals, corresponding directional air permeabilities, and air-filled porosities. Together with the results of earlier site investigations, single- and cross-hole test analyses reveal that at the Apache Leap Research Site in central Arizona: (1) the pneumatic pressure behavior of fractured tuff is amenable to analysis by methods that treat the rock as a continuum on scales ranging from meters to tens of meters; (2) this continuum is representative primarily, but not exclusively, of interconnected fractures; (3) its pneumatic properties vary strongly with location, direction and scale, in particular, the mean of pneumatic permeabilities increases, and their variance decreases with scale; (4) this scale effect is most probably due to the presence in the rock of various size fractures that are interconnected on a variety of scales; and (5) given a sufficiently large sample of spatially varying pneumatic rock properties on a given scale of measurement, these properties are amenable to analysis by geostatistical methods, which treat them as correlated random fields defined over a continuum.

Riparian and rangeland soil-vegetation-atmosphere interactions in southeastern Arizona

Scott, Russell Lawrence (The University of Arizona., 1999)

In the riparian corridor of the San Pedro River in southeastern Arizona, the fluxes of water and energy over three riparian vegetation groupings were monitored and modeled in order to determine their annual water use and water sources. In situ micrometeorological and soil moisture measurements were made from 1996-1998 at a floodplain grassland site composed mainly of the perennial floodplain grass, Sporobolus wrightii (sacaton), and a tree/shrub grouping dominated by Prosopis velutina (mesquite). The results indicate that the grassland obtained water only from the near-surface (recent precipitation), while the mesquite accessed moisture from deeper in the vadose zone and/or from the water table. Both of these sites exhibited little interaction with the underlying groundwater, suggesting that the majority of the groundwater use from riparian vegetation is limited to the areas of dense mesquite and the forest gallery adjacent to the river. Measurements of the forest gallery water use composed mainly of Populus fremontii (cottonwood) and Salix gooddingii (willow) were available for some shorter term periods in 1997. These measurements were used to calibrate the Penman-Monteith model for evaporation in order to determine the water use from the forest gallery for the entire growing season. The total seasonal water use from the forest was considerably less than potential evaporation estimates. Observations of soil moisture under two rangeland sites in the San Pedro Basin were examined in order to determine the magnitude and the depth of root zone recharge characteristics in this semiarid region. Intermittent TDR observations made from 1990 to 1998 show that deeper root zone recharge occurred primarily during the wintertime, when the plants were senescent and evaporation demand was diminished. A physically-based variably-saturated flow model was used to determine the wintertime recharge. Using an automatic calibration algorithm, the model proved capable of reproducing the observations with small error. Simulated wintertime infiltration amounts indicated that substantial, deeper root zone recharge did occur during wet winters, but that the large year-to-year variability of this recharge implies that deeper-rooted plants would still need access to moisture in shallow root zone.

Modeling of rainfall distribution, hydrologic processes and examination of model sensitivity in the context of atmosphere-land surface interactions.

Gao, Xiaogang. (The University of Arizona., 1993)

In order to improve current climate models, two issues have been recognized to be significant: (1) properly representing the precipitation distribution within a GCM grid square, (2) evaluating and improving the existing land surface hydrologic schemes. This dissertation is devoted to these issues. Precipitation affects the climate system in a variety of ways and occurs over areas that are usually smaller than the GCM grid square. This complicates the modeling of land surface processes. There are, however, stable seasonal statistical patterns underlying the observed data for a GCM grid square. A stochastic scheme was therefore proposed for the assimilation of the statistical patterns (extracted from historical data) into the land surface scheme to enhance the simulation. The required high resolution precipitation data may be obtained from satellite imagery for global application. Systematic sensitivity analyses for the Biosphere-Atmosphere Transfer Scheme (BATS) was described in this dissertation. Two types of experiments were conducted to examine the BATS performance. The first type consisted of varying 'perturbation variables' and exploring corresponding variations in energy/water states and fluxes. The employed method stressed (1) long term and multiple measures of model behavior, (2) the dominant processes under certain conditions and the proper ranges for model parameters estimates. The second type experiments applied BATS to a GCM grid covering the Lower Colorado River Basin and examined the effect of intragrid variability on land surface hydrology. The results from different spatial resolutions are compared. BATS sensitivity to initialization, atmospheric forcings, land surface properties and the computational grid size are discussed.

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