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.

A prototype raster geographic information system (GIS) for agricultural water quality analysis was developed considering the farm as an aggregation of spatial units with homogeneous physical and management characteristics. A crop model that simulates the farm and environment response to different management scenarios was integrated with the GIS. The integrated GIS-model is then run on each homogeneous area. The results of crop yield and chemical leaching are geographically referenced for further display and analysis, and to serve as an input to the decision model. A decision model based on maximization of expected utility (MEU) was also integrated to help assess and evaluate the impacts of fertilizer application on the faun system and the environment. By using utilities for both crop yield and chemical leaching the model circumvents the issue of assigning a monetary value to the environment. Accommodating both the farmers' goals, in terms of higher yield and the well being of the environment, in terms of lower chemical leaching, the model computes the expected utility of each management scenario. The management practice with the maximum expected utility is then recommended. The integrated model was tested with an example of lettuce production in Arizona. Results were compared to published field reports, the model recommendation matched well with the field results. The prototype model was simple to use, and very well integrated, which makes it an alternative to the more complex and expensive coupling of commercial GIS and simulation models.

A new Farm Package (FMP) was developed for using the U.S. Geological Survey's groundwater modeling program, MODFLOW-2000 (MF2K), to estimate irrigation water allocations to irrigation settings. The FMP dynamically integrates irrigation water demand, surface-water & groundwater supply, and return flow from excess irrigation. Routed surface-water delivery is optional, and can be simulated by coupling FMP with the Streamflow Routing Package (SFR1). MF2K with FMP and SFR1 allows estimating the allocation of surface-water and groundwater to farms for the following applications: (1) historic and future simulations, (2) water rights issues and operational decisions, (3) non-drought and drought situations. Irrigation demand, supply, and return flow are partly subject to head-dependent sinks and sources such as transpiration uptake from groundwater (formulated by FMP) and leakage between the conveyance system and the aquifer (formulated by SFR1). A steady state transpiration uptake, varying with changing water level, is stepwise linearly approximated by FMP. This was validated by ensembles of variably saturated soil column models using HYDRUS2D for different soil types, values of potential transpiration, and root zone depths. A restriction of transpiration uptake is proportional to a reduction of the active root zone. It is approximated in FMP by an analytical solution, which determines inactive ranges of the root zone with pressure heads typical for conditions of anoxia or wilting. At steady state, the transpiration uptake equaled the flux across the water table (plus the irrigation flux, if applied). Therefore, changes in soil water storage are assumed negligible. Based on this assumption, the irrigation flux required is determined in FMP by subtracting transpiratory components from natural sources (groundwater, precipitation) from a maximum transpiration uptake. This transpiratory irrigation requirement is calculated for each finite difference cell, and increased sufficiently to compensate for evaporative losses and for inefficient use. Accumulating the resulting cell delivery requirement over all cells in a farm yields the total farm delivery requirement, which is to be satisfied with surface- or groundwater. Five economic and non-economic drought response policies can be applied, if the potential supply of surface- and groundwater is insufficient to meet the crop demand. The code was verified by a hypothetical example problem run in 55 scenarios (5 drought policy scenarios x 11 parameter-group scenarios). Among all sources and sinks in a cumulative volumetric budget, 'farm well discharge,' and particularly 'farm net recharge,' were most sensitive to changes in drought policies or changes of parameters.

Thesis (M.S. - Renewable Natural Resources)--University of Arizona. / Includes bibliographical references.

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

Thesis (M.A.)--University of Montana, 2008. / Title from title screen. Description based on contents viewed Aug. 12, 2008. Includes bibliographical references (p. 86-94).

Thesis (M.S.)--Oregon State University, 1998. / Typescript (photocopy). Includes bibliographical references (leaves 103-107). Also available online.

Arizona agriculture faces many changes in the near future. One of the most imminent changes will come from the enactment of the 1980 Arizona Groundwater Management Act. The 1980 AGWMA is designed ultimately to curtail the use of groundwater in Arizona. Agriculture will be affected since this sector used approximately 87 percent of all water in the State in 1980. This study reports on the possible effects that a proposed pump tax and water duty policy would have on agriculture within the Phoenix Active Management Area. The PAMA is one of four such areas in the State that have been identified as needing groundwater use management. The results of this study indicate that the proposed water duty is more effective in curbing groundwater use than the proposed pump tax. Investment in more water application efficient irrigation technologies is also important in this study. However, substantial amounts of capital investment funds will be needed to begin this investment.