Estimation of soil and crop hydraulic properties

Authors: Strelkoff, Theodor; Clemmens, Albert; Bautista, Eduardo

Submitted to: Journal of Irrigation and Drainage Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/29/2009
Publication Date: 10/1/2009
Citation: Strelkoff, T., Clemmens, A.J., Bautista, E. 2009. Estimation of soil and crop hydraulic properties. Journal of Irrigation and Drainage Engineering. 135(5):537-555

Interpretive Summary: With increasing scarcity of water and competition for existing supplies intensifying, the need for conservation by the major water user, irrigation, becomes paramount. For well over two decades, engineers at Utah State University, the U.S. Water Conservation Laboratory, an ARS facility, and other institutions have been engaged in developing software to ease the task of action agencies, e.g., the Natural Resources Conservation Service (NRCS), in evaluating, designing, and making recommendations for managing surface irrigation systems. Surface irrigation, comprising about one half of the irrigation systems in use in the United States (well over 80% world-wide), is the least expensive in terms of capital outlay and energy costs but enjoys a poor reputation for efficiency and uniformity of application. The purpose of the software is to point the way for practitioners making recommendations for improvement. However, the recessary input data for describing field conditions (infiltration and roughness) is often unknown, and handbook values may not be useful. A number of methods for obtaining the data from simple field measurements have been published. This paper provides brief descriptions of various methods, mostly available in existing literature, emphasizing their shared approaches and individual differences. Surface-irrigation design and management software complemented by appropriate measures of field infiltration and roughness will help action agencies to put more science into the design and management of surface irrigation systems. Well designed and managed systems would benefit farmers by lowering water costs and increasing uniformity of application, environmentalists by rational reductions in diversions, the general public concerned with wise use of the water resource especially under drought conditions, state water resources agencies, and the Natural Resources Conservation Service

Technical Abstract: Some two dozen methods for estimating infiltration and roughness parameters from field measurements of test irrigations are analyzed or reviewed in this paper. They differ in their assumptions, ease of analysis, quantity of field data required, and accuracy. They are divided into two broad categories, depending upon the basic approach to determining infiltration. One features direct application of mass conservation, expressed in terms of the infiltration parameters and then inverted in some way in order to extract those parameters. The other involves repeated simulation with a sequence of values of the infiltration parameters, coupled to some kind of search procedure -- an optimization ' to minimize differences between simulation and measurement. In new findings, a one-point technique based on the Merriam-Clemmens time-rated infiltration families is documented, along with suggestions for extending existing parameter-estimation methods.