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Hydrology and Water Resources (742)

Graduate College (740)Honors College (1)Soil, Water and Engineering (1)AuthorsEvans, Daniel D. (96)Simpson, Eugene S. (79)Davis, Stanley N. (64)Ince, Simon (57)Sorooshian, Soroosh (54)Neuman, Shlomo P. (53)Davis, Donald R. (45)Maddock III, Thomas (35)Conklin, Martha H. (33)Bales, Roger C. (31)View MoreTypestext (742)Thesis-Reproduction (electronic) (545)Dissertation-Reproduction (electronic) (194)maps (3)Electronic Thesis (2)Electronic Dissertation (1)
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Worth of data used in digital-computer models of ground-water basins.

Gates, Joseph Spencer (The University of Arizona., 1972)

wo digital-computer models of the ground-water reservoir of the Tucson basin, in south-central Arizona, were constructed to study errors in digital models and to evaluate the worth of additional basic data to models. The two models differ primarily in degree of detail -- the large-scale model consists of 1,890 nodes, at a 1/2-mile spacing; and the small-scale model consists of 509 nodes, at a 1-mile spacing. Potential errors in the Tucson basin models were classified as errors associated with computation, errors associated with mathematical assumptions, and errors in basic data: the model parameters of coefficient of storage and transmissivity, initial water levels, and discharge and recharge. The study focused on evaluating the worth of additional basic data to the small-scale model. A, basic form of statistical decision theory was used to compute expected error in predicted water levels and expected worth of sample data (expected reduction in error) over the whole model associated with uncertainty in a model variable at one given node. Discrete frequency distributions with largely subjectively-determined parameters were used to characterize tested variables. Ninety-one variables at sixtyone different locations in the model were tested, using six separate error criteria. Of the tested variables, 67 were chosen because their expected errors were likely to be large and, for the purpose of comparison, 24 were Chosen because their expected errors were not likely to be particularly large. Of the uncertain variables, discharge/recharge and transmissivity have the largest expected errors (averaging 155 and 115 feet, respectively, per 509 nodes for the criterion of absolute value of error) and expected sample worths (averaging 29 and 14 feet, respectively, per 509 nodes). In contrast, initial water level and storage coefficient have lesser values. Of the more certain variables, transmissivity and initial water level generally have the largest expected errors (a maximum of 73 per feet per 509 nodes) and expected sample worths (a maximum of 12 feet per 509 nodes); whereas storage coefficient and discharge/ recharge have smaller values. These results likely are not typical of those from many ground-water basins, and may apply only to the Tucson basin. The largest expected errors are associated with nodes at which values of discharge/recharge are large or at which prior estimates of transudssivity are very uncertain. Large expected sample worths are associated with variables which have large expected errors or which could be sampled with relatively little uncertainty. Results are similar for all six of the error criteria used. Tests were made of the sensitivity of the method to such simplifications and assumptions as the type of distribution function assumed for a variable, the values of the estimated standard deviations of the distributions, and the number and spacing of the elements of each distribution. The results are sensitive to all of the assumptions and therefore likely are correct only in order of magnitude. However, the ranking of the types of variables in terms of magnitude of expected error and expected sample worth is not sensitive to the assumptions, and thus the general conclusions on relative effects of errors in different variables likely are valid. Limited studies of error propagation indicated that errors in predicted water levels associated with extreme erroneous values of a variable commonly are less than 4 feet per node at a distance of 1 mile from the tested node. This suggests that in many cases, prediction errors associated with errors in basic data are not a major problem in digital modeling.

A stochastic approach to space-time modeling of rainfall.

Gupta, Vijay K.(Vijay Kumar),1946- (The University of Arizona., 1973)

This study gives a phenomenologically based stochastic model of space-time rainfall. Specifically, two random variables on the spatial rainfall, e.g., the cumulative rainfall within a season and the maximum cumulative rainfall per rainfall event within a season are considered. An approach is given to determine the cumulative distribution function (c.d.f.) of the cumulative rainfall per event, based on a particular random structure of space-time rainfall. Then the first two moments of the cumulative seasonal rainfall are derived based on a stochastic dependence between the cumulative rainfall per event and the number of rainfall events within a season. This stochastic dependence is important in the context of the spatial rainfall process. A theorem is then proved on the rate of convergence of the exact c.d.f. of the seasonal cumulative rainfall up to the iᵗʰ year, i ≥ 1, to its limiting c.d.f. Use of the limiting c.d.f. of the maximum cumulative rainfall per rainfall event up to the iᵗʰ year within a season is given in the context of determination of the 'design rainfall'. Such information is useful in the design of hydraulic structures. Special mathematical applications of the general theory are developed from a combination of empirical and phenomenological based assumptions. A numerical application of this approach is demonstrated on the Atterbury watershed in the Southwestern United States.

Evaluation of unconfined aquifer parameters using a successive line relaxation finite difference model.

Rebuck, Ernest Charles,1944- (The University of Arizona., 1972)

A finite difference model was developed specifically for analyzing the Grand Island, Nebraska aquifer test. Time-drawdown data for the aquifer test were fitted by least squares to an exponential type equation. To facilitate calibration of the model, interpolated distance-drawdown profiles also were fitted to an exponential type equation. The treatment of aquifer boundaries and the assumption of isotropic aquifer conditions affected the model computed water table profile. The effect was significant enough as to defy making accurate estimates of saturated hydraulic conductivity and specific yield. When the analysis was extended to long time periods of discharge, problems with the boundaries, particularly the distance to the lateral constant head boundary, led to unrealistic estimates of pumping level. The finite difference technique has its greatest application as a research method for analyzing short-duration aquifer tests provided that the aquifer conditions are well defined, measurements of pumping level are available and drawdown measurements have been secured for at least two observation wells within close proximity of the discharge well. Because of difficulties in maintaining convergence and model stability, the finite difference model reviewed in this study is too cumbersome to be considered a practical, field method for the analysis of unconfined aquifer parameters.

Constructed wetlands and soil-aquifer treatment systems: Effects on the character of effluent organic matter

Quanrud, David Matson (The University of Arizona., 2000)

Within the context of potable reuse, there is a need for a more comprehensive examination of the quality of dissolved organic matter (DOM) in treated wastewater and the efficacy of different treatment schemes in removing or transforming DOM. In particular, there are significant information gaps regarding the character, fate, and health risks associated with effluent organic matter (EfOM). Two research goals guided this research. The first goal was to evaluate the efficacy of constructed wetlands for wastewater polishing in a hot, arid environment, from the perspective of season-dependent effects on DOM. To this end, behavior of organics was evaluated over a 22-month period during treatment in a local constructed wetlands facility. The second goal was to examine changes in character of EfOM that accompany passage through natural treatment systems (either constructed wetlands or soil aquifer treatment, SAT). This was accomplished via isolation and characterization of organics collected along flowpaths of these treatment systems. Wetland effluent concentrations of dissolved organic carbon (DOC) and nonbiodegradable DOC were positively correlated with temperature. That is, the highest concentrations occurred in summer and were attributed to the combined effects of evapotranspiration (ET) by wetland vegetation along with production of wetland-derived natural organic matter (NOM). There was little if any change in the hydrophobic-hydrophilic character of DOM attending wetland treatment. Biodegradation of labile EfOM combined with contribution of wetland-derived NOM resulted in modest (at best) changes in distribution of carbon moieties in hydrophobic (HPO) and hydrophilic (HPI) acid isolates. Aliphatic carbon decreased during wetland treatment. Elemental analysis suggested that microbial activity is the dominant process controlling the character of wetland-derived NOM. Reactivity of isolates in forming trihalomethanes (THMs) during chlorination increased as consequence of wetland treatment. Wetland-derived NOM was more reactive than EfOM in forming THMs. Uniform trends occurred among isolates of EfOM and wetland-derived NOM between biodegradability and THM production upon chlorination. Ultrahydrophilic EfOM was preferentially removed during vadose zone percolation of secondary effluent. The chemical character of EfOM (HPO- and HPI-acids) became more similar to NOM as a consequence of SAT. Genotoxicity of HPO-acids, on a per mass basis, increased after SAT.

The hydrology and riparian restoration of the Bill Williams river basin near Parker, Arizona

Harshman, Celina Anne (The University of Arizona., 1993)

Characterization of residual NAPL in the vadose zone using gas-phase partitioning tracers

Ross, Stephanie Danielle (The University of Arizona., 2000)

The purpose of the field experiment conducted at City of Tucson Fire Station Number 10 (Fire Station) was to conduct a gas-phase tracer test in the vadose zone in order to help determine the nature and extent of non-aqueous phase liquid (NAPL) contamination at the Thomas 0. Price Service Center (TPSC) Fire Station site. Current methods for characterization of NAPL saturation, such as soil-gas analysis and core sampling provide data only at discrete points and can be limited in their effectiveness. Gas-phase partitioning tracers can sample a larger volume of the vadose zone, allowing the location and amount ofresidual NAPL to be determined more accurately. A gas-phase partitioning tracer experiment was conducted at the Fire Station to evaluate the use of partitioning tracers in determining NAPL saturation in the vadose zone. Well R-032A was used as the injection well and well R-047A was used as the extraction well. The tracer test yielded a global retardation of 1.23, which indicates NAPL presence. A swept volume of approximately 770 m3 was contacted by the tracer and approximately 2.8m3 volumetric NAPL content was measured. However, a majority of the retention of the partitioning tracer is associated with recovery from early travel times, seen in the first peak of the breakthrough curve. Analysis of only the first peak yields a retardation factor of 1.26, a swept volume of 260 m3, and a total volumetric NAPL content of 1.lm3.

Hydrogeology of the Bird's Nest Aquifer, Uintah County, Utah

Phillips, Fred M. (Fred Melville) (The University of Arizona., 1979)

A comparison of CCM2/BATS simulated precipitation and runoff with observed values over the continental United States

Morrill, Jean Constance (The University of Arizona., 1995)

In order to evaluate the ability of general circulation models to predict future climate change, it is useful to know how realistically they simulate the current climate. Precipitation and runoff from two simulations of the National Center for Atmospheric Research Community Climate Model 2 coupled with the Biosphere-Atmosphere Transfer Scheme (NCAR CCM2/BATS) are compared to observed values over the United States. Seven different methods are used to compare simulated and observed values over several different temporal and spatial scales. Precipitation and runoff are not realistically simulated over much of the United States. Precipitation is generally too high. Simulated peak runoff occurs one to two months earlier than observed peak runoff in watersheds with a winter snowpack. Some of the errors can be attributed to coarse model resolution, which does not capture the complex sub-grid details of topography which are important factors in determining local climate.

Competitive complexation of trace metals to dissolved humic acid

Cao, Yi (The University of Arizona., 1993)

Effects of competing trace metals (10 µM) and Ca 2+ (5 mM) on Cd(II), Pb(II) and Cu(II) (0 - 100 µM) complexation by a groundwater humic acid were investigated in a series of 24 batch experiments at pH 6, 7, and 8 (I = 0.05 M). Both trace metals and Ca 2+ have little effect on Cd(II) complexation. No effect of Cu(II) on Pb(II) complexation is observed; Cd(II) appears to slightly enhance the binding between Pb(II) and humic acid. For Cu(II), the addition of Pb(II) decreases the amount of complexation, but Cd(II) also appears to slightly increase it. Calcium, however, decreases the amount of complexation in all cases. The effective binding constants determined show that the relative magnitudes of binding strengths are Cu(II) ,.., Pb(II) > Cd(II). These results indicate that in groundwaters, where more than one metal is present, the effect of other metals must be considered when predicting metal speciation.

Econometric models of domestic water consumption in the Tucson metropolitan area.

Ray, Leon Nicholas,1928- (The University of Arizona., 1972)

Data by household on water consumption and twenty-seven economic and cultural variables assumed to be related to residential water consumption in Tucson were collected. Consumption models were constructed by a linear regression computer program. To develop empirical water demand models, the classic economic demand function, C f(p), is expanded to the function, C = f(p, x₂, x₃, ..., xn ), where p is Price, and x₂, x₃, •.., xn are other variables. Both mean household consumption and variability among households decrease as water price increases. In the lowest water price area water consumption was correlated significantly to the property value and pipe diameter at the meter, and slightly less significantly correlated to number of bathrooms and number of trees. In the second highest price area consumption was strongly correlated to property value, pipe diameter, number of bathrooms, number of trees, having a dishwasher, automatic clothes washer, garbage disposal, lawn, lawn area, sprinkling system, whether property value is more than $40,000, and whether the lawn is watered in the summer; it is moderately correlated to the number of people per house and negatively correlated to having an evaporative cooler.

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