Author
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Replogle, John |
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Submitted to: Technical Conference on Irrigation Drainage and Flood Control
Publication Type: Proceedings Publication Acceptance Date: 6/6/1998 Publication Date: N/A Citation: N/A Interpretive Summary: Irrigated agriculture grows one-third of the total crop harvested. This irrigated harvest is produced on one-sixth of the world's crop land and is worth one-half of the crop value. Without irrigated agriculture, expansion of cropped land into humid areas would surely be needed to avoid world starvation. Strong political and economic pressures on the remaining rainforests of the world would threaten their continued existence. As it is, irrigated agriculture must significantly improve efficient crop production to outpace the world's population bulge, expected to peak above 10-12 billion people, and still protect the environments of the world in a meaningful sense. Most of this irrigation infrastructure of the world is approaching the economic end of its life cycle and is due for rehabilitation. The deterioration contributes to inefficient irrigation and acerbates salinity problems. Emphasis worldwide is on some form of rehabilitation. This paper urges upgrading of the systems instead of simpl rehabilitation and provided guidance on potential improvements. This upgrading and modernization includes automatic water conveyance control in large canal systems that can allow delivery canal systems to more closely match the on-farm water delivery needs and improve production efficiency. Even when funding is not available to automate, measures that can be incorporated into an annual maintenance process that will enhance current manual operations and still not hamper future automation, are offered. Some of these include changes in existing canal structures and hardware, and changed operating procedures. The discussion offers many points to advisers of irrigation projects who must concern themselves with site-specific limitations in funding and social issues. Technical Abstract: Because many of our world irrigation systems are well into the late years of their economic design life, efforts today are to rehabilitate and modernize. Modernization is widely recommended over simply rehabilitating to original status. Several goals of modernization include providing flexible water delivery policies that are responsive to modern, on-farm irrigation systems, such as drip, sprinkler, level basin, and surge. This implies that the farm unit has access to the water supply in a meaningful way through the provision of demand or arranged delivery policies. This in turn often appears to require automation of the delivery system for implementation. However, there are a number of structural and management changes that can be considered that require only limited automation, or no automation, and can still provide significant flexibility of irrigation delivery to the farm unit. These measures include appropriately designed combinations of canal level-control structures, field outlet structures, strategically placed off-line reservoirs, flow-measurement devices, and canal operating procedures. How to retrofit these useable features into an existing system as part of the rehabilitation and modernization scheme is the major emphasis of the paper. These features encourage higher production while maintaining good irrigation efficiency. |
