A computer model for use in predicting the impact of various improvement options on command area expansion of a deep tubewell irrigation system has been developed. A field study was conducted on 11 selected deep tubewells located at two sites, namely Dhamrai and Thakurgaon, in Bangladesh to collect necessary physical data to provide irrigation engineering insight and a basis for testing and application of the model. The results of the investigation revealed that the actual discharge of most of the deep tubewells was lower than the design or rated capacity. The duration of pump operation in the majority of the study deep tubewell areas was extremely low. The conveyance losses in all of the study systems were very high. Even though a portion of those losses was reused in the system, particularly in rice growing areas, they caused serious difficulty in delivering water to remote fields, thus, restricting the command area. The overall irrigation efficiencies in all of the wheat growing areas of Thakurgaon were low. Considerable losses and waste of water after it was diverted from the field channels due to lack of leveling and poor water control were mostly responsible for the low efficiencies . Excessive percolation losses due to inadequate puddling of the soils during land preparation and frequent drought conditions resulted from poor distribution of water in some of the rice growing areas of Dhamrai caused relatively low overall irrigation efficiencies. The overall efficiencies of the pumps both driven by diesel engine and electric motor were found to be much lower than the recommended values. The developed model was applied to predict the expected command area under both existing and modified physical conditions. The model predicted command areas were compared with the actual field observed values and necessary adjustments were discussed. The impact of each of the improvement alternatives considered in the study was determined by comparing the predicted command area under the modified conditions with that under the existing physical settings. An economic analysis was performed to determine the cost effectiveness of most of the alternatives. Application of the model in evaluating the farmers' pump operation practices was demonstrated. Use of the model to assist the farmers in planning the command area and delivery schedule was also indicated. Although the model was developed to use in a deep tubewell irrigation system, it can also be used in the system served by a low-lift pump or by a turnout in a large irrigation project.

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Typescript (photocopy). / Digitized by Kansas Correctional Industries

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Three cotton (Gossypium hirsutum L.) cultivars were grown under field conditions at Eloy, AZ in 1985 and 1986 to investigate the effects of five drip irrigation treatments on yield, petiole nitrate concentrations, and fruiting characteristics. Irrigation treatments ranged from 59 to 86 cm applied during the growing season. Petiole samples were collected once a week and analyzed for nitrate content. Flower and boll numbers and yield data were recorded throughout both years. Results indicated that irrigation treatments had significant effects on yield with lower amounts of irrigation producing significantly lower lint yields. Significantly lower nitrate concentrations were also observed among the lower irrigation treatments. Irrigation treatments affected flower and boll production with lower irrigation treatments producing fewer flowers and bolls. Irrigation treatments did not significantly influence percent boll set, however, percent boll set was lower in the higher irrigation treatments. The higher irrigation treatments also produced heavier bolls.

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Policy analysts designing programs to improve the efficiency and expand the use of water in the irrigation of farm lands often enlist benefit-cost analysis as a means of assessing impacts and feasibility. While on-site comparisons of costs and benefits are important factors in project assessment, other dimensions such as risk, income distribution and offsite impacts may be overlooked. In this research a more complete approach to project analysis was sought. A simulation model of a river basin was developed. Paris Creek, Idaho, an area studied recently by the U.S. Soil Conservation Service, was the representative project location analyzed. An important design goal was to provide an analytical data processing template applicable to future studies. Paris Creek farmers are directly dependent on water available from Paris Creek. However, most years the flow is insufficient to provide adequate irrigation with present methods. High pumping costs, high seepage losses in delivery systems and low on-farm irrigation efficiencies compound the problem. A proposed improvement plan is analyzed, involving piped gravity-fed delivery systems and conversion from surface to sprinkler irrigation. Installation and government consulting costs are to be shared by the farmers and S.C.S. The computer model simulated monthly stream flows, irrigated crops, measured impacts, computed production benefits, and compiled costs and benefits affecting farmers and society. A 50-year project life was assumed, and statistics were collected for 25 separate iterations. It was determined that north group farmers are almost always better off with the project when annual comparisons were made between conditions. Only in years of very low stream flow would farmers lose more money with the project. However, substantially higher variability in annual income could be expected, a condition of greater risk to farmers. Society as a whole was also found to experience an increase in net benefits, but not as great as for farmers and with greater annual variability. The model was effective in providing information about risk and income distribution. However, difficulty remains in assessing offsite impacts because there lacks an effective approach and appropriate data. / Graduation date: 1986