Thesis (M.S.)--Montana State University--Bozeman, 2007. / Typescript. Chairperson, Graduate Committee: Alexander V. Zale. Includes bibliographical references (leaves 84-96).

Thesis (Ph. D.)--University of Wyoming, 2006. / Title from PDF title page (viewed on June 30, 2008). Includes bibliographical references (p. 96-98).

Thesis (M.S.)--Montana State University--Bozeman, 2005. / Typescript. Chairperson, Graduate Committee: Alexander V. Zale. Includes bibliographical references (leaves 70-78).

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Science, 1981. / Microfiche copy available in Archives and Science / Vita. / Bibliography: leaves 170-178. / by Kevin Michael Bohacs. / Sc.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Science, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND LINDGREN. / Bibliography: leaves 176-181. / by William Charles Corea. / Ph.D.

The objective of this study was to develop a numerical model which predicts the geometry of an optimal straight stable channel for a given set of conditions: (1) the submerged coefficient of static friction of the channel bed material, (2) lift-to drag ratio, (3) grain size of the bed material, (4) water discharge, and (5) longitudinal slope of the channel. The term optimal stable channel refers to a channel capable of transporting sediment along a flat bed but whose banks are barely stable, i.e., all particles lying in the bank region are on the verge of motion. In addition to the geometry of the optimal stable channel, the model determines the critical and actual stress distributions along the perimeter of the channel cross-section. The model is based on the turbulent diffusion concept, which takes into account the diffusion of downstream momentum from the center of the channel towards its banks, due to Reynolds stresses. This causes a redistribution of stress along the channel perimeter. The resulting shear stress decreases monotonically as the lateral distance from the center of the channel increases. With such a distribution, it is possible for the stress to be above critical in the flat bed region, and below or at critical in the bank region. Thus, it allows for the coexistence of a mobile bed and stable banks; a phenomenon commonly observed in natural streams and laboratory flumes but not possible to explain on the basis of the threshold channel theory. Special attention is given to the area in the vicinity of the junction of the bed and bank, because of a discontinuity in the curvature of the bank profile that exists right at the junction point. This discontinuity, or step function, has been ignored by other researchers, although it can significantly influence the shape of the bank profile. A dirac delta function is used here for the third derivative in order to remedy the problem. By numerically integrating the third derivative, the change in the step function at the junction point can be determined. Regime relations are proposed based on numerical model calculations. The results of the numerical model compare favorably with existing laboratory and field data. It was found that the banks of an optimal stable channel are closely described by a fifth degree polynomial, which differs from the cosine, exponential, and parabolic profiles suggested by earlier investigators. It was also determined that the geometry of a threshold channel differs from that of a wide channel. / Master of Science

Master of Science

Thesis (Ph.D.(Civil Engineering))--University of the Witwatersrand, Faculty of Engineering, 1966.

Furrow irrigation is the dominant practice for irrigating row crops in the western Treasure Valley region near Ontario, Oregon. Though improvements have been made in management practices over the years, excessive runoff and deep percolation are still important problems contributing to surface water and groundwater degradation. Field observations were made during two growing seasons to establish a data base from which the hydraulic surface irrigation model, SRFR (SRFR, a computer program for simulating flow in surface irrigation, developed at the U.S. Water Conservation Laboratory in Phoenix, Arizona (Strelkoff, 1991)), could be calibrated. SRFR is a numerical model, based on the principles of open channel hydraulics coupled with an empirical relationship characterizing furrow intake. SRFR is an analytical tool, with which the user supplies the physical parameters (such as furrow shape and furrow intake) and also the management variables (inflow rate and duration of inflow), and a simulation is conducted based on these conditions. Therefore, this model is a tool which provides insight into furrow irrigation processes. More specifically, SRFR can help answer such questions as which factors at the time of the irrigation are most important in determining irrigation performance. Once calibrated for a given set of conditions, various management strategies may be evaluated as to their relative effectiveness. These strategies may include, but are not limited to, cut-back irrigation, surge irrigation, alternating furrow irrigation, and laser-leveling of the field. A broad data-base is necessary for model calibration and to develop an understanding of it's limitations. Measurements of furrow intake, stream advance times, inflow and outflow, hydraulic roughness and furrow shape were obtained from several sites and irrigation events. These sites represent several crops, field lengths, field slopes, and soil textures. Using these data, a model calibration procedure was developed which matched irrigation inflow and outflow volumes and stream advance times for a given irrigation event. The calibration procedure is used to help identify those model input parameters that best describe a given irrigation event. This thesis is to provide a broad understanding of furrow irrigation systems in northeast Malheur County, recommended hydraulic parameters for use with SRFR, and the practical limitations of such hydraulic irrigation models. Irrigation performance is largely determined by the intake characteristics of the soil at the time of irrigation. Field conditions vary greatly depending on the crop, soil moisture, number of irrigations, tractor traffic, field slope, furrow shape and field history. The grower has control over only two variables which determine irrigation performance: inflow rate and duration. A difference in intake and irrigation performance was found to exist between non-wheel and wheel traffic furrows. These differences became less noticeable late in the season. Straw mulching greatly increases the furrow hydraulic roughness and therefore increases stream wetted perimeter and advance time. Vegetative interference from crops such as potato and sugar beets increase furrow hydraulic roughness late in the season. Initially, furrow shape depends on the crop and which cultivating implement is used. Furrow shape may evolve during the growing season depending on field slope, flow velocities, crop stand and the presence of crop residues and straw mulch. / Graduation date: 1996

Deep interceptor drains are commonly used to control canal seepage in southern Alberta, Canada. Recently, shallow grid drainage was introduced. A study was initiated in 1987 to assess the effectiveness of grid drainage to intercept canal and natural groundwater seepage and reclaim the resulting saline affected land. / Using a groundwater flow model, MODFLOW, it was found that a single deep interceptor drain would have failed to intercept all canal seepage and maintain the water table downslope of the canal below the 1.0 m design water table depth. Conversely, simulations indicated that with a grid drainage system, all canal and natural groundwater seepage would be intercepted and the water table would remain below the design water table depth, with or without irrigation recharge that would maintain a steady state salt balance. / The benefits of fall irrigation were demonstrated using three test plots near the canal.