Author
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Strelkoff, Theodor |
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Clemmens, Albert |
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Submitted to: Book Chapter
Publication Type: Book / Chapter Publication Acceptance Date: 6/15/2007 Publication Date: 10/2/2007 Citation: Strelkoff, T., Clemmens, A.J. 2007. Chapter 13. Hydraulics of surface systems. 13:437-498. Interpretive Summary: Nearly one half of the 21 million hectares of irrigated land in the U.S. is served by surface systems. The percentage increases to well over 90% in other parts of the world. It is in most cases the cheapest method of applying water to crops, and usually requires the least expenditure of energy, but it is often viewed as inherently wasteful of water. Yet, under appropriate field conditions, proper design and management of surface systems can lead to high application efficiencies, on a par with other methods. Design of surface systems has traditionally been based on experience with successful projects, intuition, empirical compilations, and not very much theory. Now, however, many of the analytical problems associated with the prediction of surface-irrigation flows have been solved, and it is possible to develop designs and operating recommendations based on simulations. The chapter provides an overview of simulation techniques especially for the NRCS, universities, and irrigation consultants. The goal is the development of surface-irrigation systems that can be operated in an efficient, effective, sustainable, and environmentally sound way. Technical Abstract: The goals of surface irrigation are defined and the physical processes involved are described. The field variables such as slope, infiltration, and roughness, the physical design variables like furrow or border cross section and length of run, and management variables such as inflow and outflow control are discussed. The role of modeling as a tool for subsequent design and management is emphasized, as is the pivotal role of physical laws such as conservation of mass and momentum. Hydrologic, or lumped-parameter, modeling is described in detail as a relatively simple technique sufficiently accurate for many purposes. The errors that do arise are explained as a consequence of some of the assumptions made to achieve the simplification. The hydrodynamic, or distributed-parameter, approach, itself amenable to a series of simplifications, is described, with sufficient detail intended to afford a basic understanding of the assumptions and solution techniques. A user-friendly software package allowing easy data entry and simulation graphical output is introduced. The chapter closes with a discussion of techniques for estimating infiltration and roughness in the field for entry into simulation and design software. |
