Thesis (M.S. - Hydrology and Water Resources)--University of Arizona. / Includes bibliographical references.

Thesis (Ph. D. - Economics)--University of Arizona, 1983. / Includes bibliographical references (leaves 137-140).

Agricultural production is affected by a range of policy and climatic variables. This research explored the impacts of cap and trade, climate change and agricultural policy scenarios on water resource use and allocation in agricultural production. The research is organized into three separate studies, one for each set of scenarios.The first study focused on cap and trade policy for controlling greenhouse gas emissions, combining cost of production estimates with output price projections to determine the overall economic impact of cap and trade legislation, as well as its impact on agricultural water consumption. Price projections that included carbon offsets were higher than projections that did not, due to land being taken out of production and prices being bid up. HR2454 will increase production costs, particularly energy intensive inputs. Output prices increase as producers reduce production in response to cost increases. If agricultural offsets are allowed, output prices will be bid up further. Offsets allow producers to receive payments for cutting emissions. Producers benefit due to indirect price effects. Since water is quantity limited, total water use is unchanged.The next study looked at the physical impacts of climate change on production, particularly rising temperatures and carbon dioxide concentrations. By analyzing the anticipated yield effects, it was found that overall net incomes would decrease and the water constraint would remain binding - meaning total water use is unchanged.The third paper analyzed the effects of agricultural policy on land and water resource allocation. Cotton is directly subsidized. Corn and grain sorghum are subsidized indirectly through ethanol subsidies. Sugar cane prices are artificially high due to tariff rate quotas on sugar imports. Removal of any of these interventions decreased net profits to producers, but water use remains unchanged. Removing all farm programs significantly decreases acres under cultivation, and reduces water use below the water constraint. It comes at a great cost to producers however, given the small amount of water saved.

The economic efficiency of water development in Utah, including transfer systems, has seldom been examined, nor has the costs of public policies which result in deviations from efficient allocations. In order that public officials be better informed about water allocations , the present effort examines the efficient allocation of water in time frames up to 2020 under several alternative assumptions and calculates the cost of alternative policies. Us ing mathematical programming techniques, a computer mode l is developed to determine the supply (marginal cost) and demand (value of marginal product) relationships for agricultural water, given depletions for municipal and industrial (M & I) and wetland requirements. The model maximizes net profit per acre t o an average agriculturalist in each of ten study areas in Utah. Proposed interbasin transfers and their costs are included in supply. The optimal solution gene rated is an efficient allocation, since maximization of net profits occurs only when value of marginal product equals marginal cost. The requirements for M & I water are projected into the future using trending and probable industrial development. An efficient allocation (optimal solution) is generated by the model f or 1965, 1980, 1990, 2000, 2010, and 20 20. Th e timing of investments in water distribution systems can be determined from these solutions. Using alternative assumptions about policies (minimum inflows to Great Salt Lake and water salvage) several alternative temporal distributions are determined. Additionally, the effect of restrictions on groundwater pumping (present levels of storage must be maintained) are examined. The costs to users in higher supply curves (marginal costs) are approximated by areas between supply curves. In addition, losses to agricultural users from diminished efficient new production can be approximated. The critical factors in large proposed water transfers in Utah appear to be the growth of M & I requirements along the Wasatch Front, particularly in the Jordan River Basin. Sufficient water is available in the Colorado River Basins to provide maximum transfers, full oil shale and power generation development, and efficient agricultural production. Restrictions on groundwater pumping and water salvage in the Jordan River Basin and maintenance of high inflows to Great Salt Lake make transfers necessary sooner. The costs of such restrictions approaches 25 percent of the total investment by agriculture in transfer systems. If no r e strictions are made, but investment in these systems occurs now, a loss of foregone returns to alternative investment equal to about 70 percent of the total agricultural investment is incurred by society.

Nutrient mitigation capacity of low-grade weirs in agricultural drainage ditches

Thesis (Ph. D. in Economics)--Vanderbilt University, Aug. 2007. / Includes bibliographical references (p. 120-128).

Thesis (Ph. D.)--University of California, San Diego, 1993. / Photocopy. Ann Arbor, Mich. : University Microfilms International, 1994. 21 cm. Includes bibliographical references (p. 577-592).

Thesis (Ph. D. in Economics)--Vanderbilt University, Aug. 2007. / Title from title screen. Includes bibliographical references.

Foodborne outbreaks have continued to be associated with produce contamination originating from on-farm sources, such as soil or agricultural water. Additionally, the heterogeneity of the pre-harvest environment complicates the development of universal strategies for managing produce safety risks. Understanding the ecology and epidemiology of foodborne pathogens and fecal indicator bacteria (FIB) by growing regions, sample types, scale of analysis, and detection method is essential for developing targeted mitigation strategies. This dissertation utilized quantitative research methods and statistical modeling to examine the impact of sampling method, spatial, temporal, meteorological, and physicochemical factors on pathogen prevalence and FIB levels. Key findings highlight that the drivers of prevalence differ between pathogens and were influenced by sample type, scale, and region.. The variations in associations emphasize that risk varies by space and time. Therefore, results support regional and scale-dependent food safety standards and guidance documents for controlling hazards to minimize risk. Additionally, the method used for pathogen detection influences prevalence highlighting the need for standard methods since methodological differences confound comparisons across studies. Furthermore, since agricultural water quality is an important food safety priority, this dissertation aimed to determine the efficacy of chemical antimicrobial sanitizers against Salmonella in pre-harvest agricultural water. Results demonstrated that certain sanitizer treatments and conditions can significantly reduce Salmonella populations in preharvest agricultural water sources and thus may serve as a risk reduction option when used correctly. / Doctor of Philosophy / Fresh fruits and vegetables are continually implicated in foodborne outbreaks. Additionally, the source of the pathogen that causes illness in these outbreaks is often due to contact with contaminated soil or water on the farm. Since the environment is extremely diverse, the risk of foodborne pathogens is not uniform across a farm and between farms. Therefore, the development of a one-size-fits-all plan to reduce the risk of foodborne pathogens from contaminating produce on a farm is difficult. Understanding the incidence and distribution of foodborne pathogens and fecal bacteria and how these microorganisms interact with the environment is important to develop strategies to manage risk. Additionally, understanding how the prevalence of bacteria varies by state, medium (water vs soil), and farm is needed to develop targeted mitigation plans. This dissertation utilized laboratory and field-based experiments to understand how space, time, weather, and physical properties impact the occurrence of foodborne pathogens and fecal bacteria. The primary results show factors that impact prevalence are different between pathogens (Salmonella vs Listeria vs E. coli). Furthermore, the occurrence differed by sampling method (molecular vs culture), sample type (water vs soil), scale (within a farm vs between multiple farms), and region emphasizing that the risk from foodborne pathogens varies over space and time. Overall, this dissertation's results suggest that both regional and scale-specific guidelines are needed to reduce foodborne pathogen risks in the farm environment. Lastly, since the quality of the water used in growing fresh produce is an important food safety priority, the effectiveness of chemical antimicrobial sanitizers against Salmonella in agricultural water was evaluated. Results demonstrated that certain sanitizer treatments and conditions (sanitizer concentrations, water temperatures) can significantly reduce Salmonella populations in pre-harvest water sources and may serve as a risk reduction option when sanitizers are used correctly.

Irrigation systems are designed to deliver water to crops, but their efficacy varies widely due to operational decisions, weather variability, and water availability. The operation of an irrigation system is studied in this dissertation to determine irrigation performance and potential for improvement.Satellite remote-sensing was used to determine inter-annual variability in crop evapotranspiration and link it with weather patterns and operational decisions. A decade was studied to include several dry, wet and average years of snowfall. It was found that the irrigation district has the capacity to buffer a dry year, but crop evapotranspiration patterns indicated that the buffer capacity of the irrigation district is limited in a second dry year. Studying the current operations of an irrigation system also requires an analysis of the spatial variability within the system to identify potential areas for improvement. Achieving such information is challenging due to the spatial heterogeneity between farm fields. The Ador irrigation system simulation model is used in this study with satellite remote sensing data, which were combined in the calibration and validation process to ease the re-adjustment of management parameters. This approach provides a cost-effective and innovative method for model simulation when field observations are limited. Alternative water delivery scenarios were simulated with the Ador irrigation system simulation model to quantify changes in the water balance, irrigation performance, and water productivity. Results for implementing a minimal irrigation time indicated that irrigation events occurred with a higher frequency and reduced crop water stress. Water productivity for the irrigation district increased substantially in this scenario, whilst district water savings were achieved by diverting less irrigation water. Advantages are only achieved if farmers collectively make the decision to change. A water accounting analysis is required to examine if water savings are achieved at basin scale. There is a potential for the rebound effect to occur, which suggests that an increase of water efficiency causes the increase of water consumption. Simulation results indicated that if the efficiency is increased through improvements of the water delivery, the water consumption increased. Water savings achieved by reducing irrigation diversions did not compensate for the decrease in drainage that downstream users depend on.