This thesis is concerned with a mathematical study of several problems involving infiltration from irrigation channels into an unsaturated homogeneous soil. All the problems considered are two dimensional and are solved numerically by employing boundary integral equation techniques. In the first chapter I introduce some of the literature and ideas surrounding my thesis. Some background information is stated followed by an outline of the thesis and a list of author’s published works that support the material in the thesis. Full descriptions of the fundamental equations used throughout the thesis are provided in chapter 2. Chapter 3 contains the first problem considered in this thesis which is infiltration from various shapes of single and periodic irrigation channels. Specifically strip, semi-circular, rectangular and v shaped channels. The solutions are obtained using the boundary element technique. The solutions are then compared with the results obtained by Batu [14] for single and periodic strip sources. In chapter 4 a boundary integral equation method is adopted for the solution of flow from single and periodic semi-circular channels into a soil containing impermeable inclusions. The impermeable inclusions considered are of rectangular, circular and square shapes. The aim is to observe how the various shapes of inclusions can affect the direction of the flow particularly in the region adjacent to the zone where plant roots would be located. Chapter 5 solves the problem of infiltration from single and periodic semicircular irrigation channels into a soil containing impermeable layers. A modification is made to the boundary integral equation in order to include the impermeable layers with the integration over the layers involving Hadamard finite-part integrals. The objective of the work is to investigate how the number and the depth of the impermeable layers affects the flow. Chapter 6 employs a particular Green’s function in the boundary integral equation. The Green’s function is useful for flow from a single channel since it removes the need to evaluate the boundary integral along the soil surface outside the irrigation channel. A time dependent infiltration problem is considered in chapter 7. The Laplace transform is applied to the governing equations and the boundary integral equation technique is used to solve the resulting partial differential equation. The Laplace transform is then inverted numerically to obtain the time dependent values of the matric flux potential. / Thesis (Ph.D.) - University of Adelaide, School of Mathematical Sciences, 2008

Seasonal trends in water table level and soil moisture for four plant community types within an irrigated eastern Oregon riparian zone were described. Aboveground biomass, species composition, litter, percent bareground and percent basal cover of key plant species and life forms were measured. The relationship between water table levels and soil moisture content were analyzed using simple linear regression. Transition zones between plant community types based on soil moisture and/or depth to water table during the growing season were determined. The soil moisture-water table relationship can be used to predict changes in plant community composition induced by a permanent depth to water table change. Irrigation impact on meadow water table levels and stream temperature were determined. Water table levels responded to irrigation manipulations within days. The permanent cessation of irrigation would shrink the riparian meadows contained within this study from widths in excess of 300 m to less than 60 m. Continuous stream temperature data were collected on a stream running through adjacent non-irrigated and irrigated meadows. Daily maximum stream temperatures in the segment contained within the irrigated meadow were 1.0�� to 3.0�� C cooler than the reach contained within the non-irrigated meadow. Management impact on plant community attributes, forage production and forage quality were assessed under three pasture management alternatives. Comparison of stubble height, litter, forage production, forage quality, species composition, percent bareground and percent basal cover of key plant species and life forms indicated all three management alternatives are sustainable from both a plant community and a livestock production perspective. / Graduation date: 1996

This study examined the effects of a microbubble emulsion (ME) combined with sonic or ultrasonic agitation, on irrigation dynamics and reduction of biofilm bacteria. High-speed imaging was used to characterize the bubble dynamics generated in ME by sonic or ultrasonic agitation within polymer teeth. 5.25% NaOCl or ME was sonically or ultrasonically agitated in canals of extracted teeth with 7-day-old Enterococcus faecalis biofilms. Dentinal shavings were sampled and colony-forming units (CFU) enumerated. Mean log CFU/ml values were analyzed with ANOVA and post-hoc tests. Strongly oscillating and vaporizing bubbles were generated within ME during ultrasonic, but not sonic agitation. Post-treatment biofilm CFU were significantly lower in the ultrasonic agitation (P=0.000) of ME group than in the ultrasonic (P=0.009) and sonic agitation (P=0.006) of NaOCl groups. The synergistic effect of ME combined with ultrasonic agitation enhanced bubble dynamics and reduced E. faecalis biofilm bacteria beyond the level achieved by agitation of NaOCl.

This study examined the effects of a microbubble emulsion (ME) combined with sonic or ultrasonic agitation, on irrigation dynamics and reduction of biofilm bacteria. High-speed imaging was used to characterize the bubble dynamics generated in ME by sonic or ultrasonic agitation within polymer teeth. 5.25% NaOCl or ME was sonically or ultrasonically agitated in canals of extracted teeth with 7-day-old Enterococcus faecalis biofilms. Dentinal shavings were sampled and colony-forming units (CFU) enumerated. Mean log CFU/ml values were analyzed with ANOVA and post-hoc tests. Strongly oscillating and vaporizing bubbles were generated within ME during ultrasonic, but not sonic agitation. Post-treatment biofilm CFU were significantly lower in the ultrasonic agitation (P=0.000) of ME group than in the ultrasonic (P=0.009) and sonic agitation (P=0.006) of NaOCl groups. The synergistic effect of ME combined with ultrasonic agitation enhanced bubble dynamics and reduced E. faecalis biofilm bacteria beyond the level achieved by agitation of NaOCl.

This study presents a diagnostic analysis of how two types of governance structures (water user associations versus collective irrigation institutions) at Hubei, issue their impacts on local irrigation governance and management, to produce a collective action outcome in irrigation systems. In particular, it focuses on (1) at the meso level, institutional analyses of irrigation management incorporate physical, community, and institutional attributes, and their interactions to configure possible pathways to collective outcomes within Hubei’s settings, and (2) at the micro level, the underlying mechanisms that offer individuals incentives to cooperate with each other for irrigation activities. Drawing upon a theoretical debate about rationales for promoting or limiting the establishment and development of water user associations, and empirical puzzling phenomena observed in Central China, three research hypotheses are posited accordingly. Determinants of collective outcomes in local irrigation governance and management are highlighted from irrigation literature. Employing Elinor Ostrom’s Institutional Analysis and Development Framework, an analytical framework exploring irrigation governance patterns in Central China is introduced. A mixed research method is applied in this study. At the meso level, 32 irrigation systems are selected to run a Qualitative Comparative Analysis; at the micro level, four irrigation systems are identified out for an in-depth comparative case study. In the end, three pathways to collective action, and four pathways to water adequacy, are generalized respectively. Evidence from 32 irrigation systems in central China indicates that both WUA-managed irrigation systems and collective irrigation systems have the capacity to organize collective irrigation activities successfully in local settings. For one thing, WUA is only one of the many factors affecting collective outcomes, and that the impact of WUA really depends on how it is nested within the larger configuration of factors; thus, challenging the belief of many government officials and analysts that WUA institution is a panacea for irrigation problems. For the other, collective irrigation systems could also achieve collective action, if attributes configured appropriately. This demonstrates that collective irrigation institution, in and of itself, is not automatically malign; given this, moves towards participatory governance do not necessarily render traditional hierarchical government interventions obsolete. Last but not least, this study also identifies a third governance institution, namely, the lineage group. Findings indicate that as informal solidary entities, lineage groups have important contributions to rural governance, as long as they are nested within the appropriate attributes configurations. Referring to the pathways to water adequacy, it is found that the emergence of collective action alone does not necessarily translate into water adequacy at the tail end of the irrigation systems. The four case studies not only entail some pathways to collective action, but also exemplify complicated and diverse reasons that might lead to collective failures. Comparing the successful cases with the failure ones, boundary rules, position rules, choice rules, and payoff rules explain the systematic differences at the operational level, while information rules, aggregation rules, and scope rules that operate at the collective level, appear to have minimal effect here. / published_or_final_version / Politics and Public Administration / Doctoral / Doctor of Philosophy

Rising water costs and concern for groundwater contamination are forcing melon growers to improve irrigation and nitrogen fertilization efficiency. The research objectives were: 1) to determine quantities of nitrogen and water applied through a subsurface drip irrigation system to cantaloupe and watermelon which would optimize fruit yield while minimizing losses of nitrogen and; 2) to develop specific monitoring techniques for assessing the water and nitrogen status of melon crops throughout the growing season. Four years of field research were conducted from 1988 to 1991 at the University of Arizona Maricopa Agricultural Center, Maricopa, AZ. The first two years of research determined which varieties of cantaloupe and watermelon would grow best under drip irrigation and the feasibility of using plant tissue tests to aid in N fertilizer scheduling. The last two years of research used a factorial design with levels of N and target soil water tension to determine response surfaces for fruit yield and net return. Information from tensiometers was used to schedule irrigations. Watermelon petiole nitrate levels at critical growth stages were used to recommend application rates of nitrogen fertilizer. In 1991, an N difference method was used to estimate N which was unaccounted for in this watermelon cropping system. Petiole nitrate levels were highly responsive to N fertilizer treatments and accurately quantified visual observations of crop N status. Petiole nitrate results also indicated that preliminary nitrogen fertilizer management guidelines using a tissue nitrate test was reasonably accurate in predicting optimum nitrogen 'management. Market able yield showed a soil water tension by N interaction. Maximum marketable yield was estimated to be 101 Mg ha⁻¹ at 7.2 kPa tension and 336 kg of applied N ha⁻¹. Maximum net return was estimated to be $8 250 ha⁻¹ when average soil water tension was 10.6 kPa and applied N was 243 kg N ha⁻¹. Unaccountable N was estimated to be 300 kg N ha⁻¹ when N rates were 500 kg ha⁻¹ and average soil water tension was 4 kPa. A response surface was estimated through the transformation and summation of yield, net return and unaccounted for N response variables. The optimum average soil water tension and rate of applied N were 12.6 kPa and 181 kg N ha⁻¹, respectively.

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Reviewed 06/2015; Originally published: 02/2001 / 5 pp. / In this article we will discuss various aspects of soil evaluation including physical examination, soil sampling and analysis, and soil test interpretation. We will also discuss how these approaches to soil evaluation can be incorporated into both short- and long-term management plans.

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