MANAGEMENT STRATEGIES FOR GRAVITY SPRINKLE IRRIGATION SYSTEMS

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Author

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Department of Engineering

ABSTRACT
Management Strategies for Gravity Sprinkle Irrigation Systems by Aliyu Abubakar Ramalan, Doctor of Philosophy Utah State University, 1988 Major Professor: Dr. Robert W. Hill Department: Agricultural and Irrigation Engineering The study reported herein examined various management strategies which can be implemented for equitable allocation of water among users of a gravity sprinkle irrigation system. A computer model was developed and employed to effect allocations accordingly. Sequencing users to a schedule of when to draw water from the system was included to maintain mass balance. Historical streamflow records and other climatic data for three years, 1979, 1986, and 1983, representing normal, dry, and wet years, respectively, were used. The equity aspects of water distribution were addressed, taking into account the shares of stock held in the irrigation company by each user. Allocations were proportionately determined for the individuals in relation to the numeric strength of the users' shares when demand was constrained by available streamflow. Diversions at turnouts in times of water shortage were strictly according to water rights. The developed water management strategies were applied to a real-life irrigation project, the Richmond Irrigation Company, Richmond, Utah.  The criteria, described as strategy attributes, provided quantitative assessment of the strategies. The quantitative assessments were based on cost-benefit analysis, waiting time, and the resource-utilization ratio. The waiting time was estimated, but the assessment of its social repercussions beyond reducing available soil moisture and its resulting effect on crop yield were deemed outside the scope of the study. Using pertinent crop, soil, water right, and historical data on streamflow and climate, the model determined the number of users irrigating, and the supply and demand flow hydrographs daily. At the end of the season, expected actual crop yields for the user/field were estimated, in addition to the other strategy attributes. Allowing users unlimited access to water, a pure on-demand strategy, was most beneficial in terms of gross benefit to project; costs of augmentation were not included. There were no significant differences among the performances of all modified rotation strategies, and they were excelled by the non-rotation strategies except One-time delivery. One-time delivery recorded a waiting time or stress days of 101 days in the dry year, the highest among all strategies. The resource-utilization ratio ranged from 0.32 to 1.84, with higher ratios indicating a need for supply augmentation.