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Title: COMPARISON OF HYDRUS-2D SIMULATIONS OF DRIP IRRIGATION WITH EXPERIMENTAL OBSERVATIONS

Author
item Skaggs, Todd
item Trout, Thomas
item SIMUNEK, JIRI - UC RIVERSIDE, CA
item Shouse, Peter

Submitted to: Journal of Irrigation and Drainage Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/23/2003
Publication Date: 8/1/2004
Citation: Skaggs, T.H., Trout, T.J., Simunek, J., Shouse, P.J. 2004. Comparison of HYDRUS-2D simulations of drip irrigation with experimental observations. Journal of Irrigation and Drainage Engineering. 130(4):304-310.

Interpretive Summary: As the population grows and urban water use increases, irrigated agriculture is being called on to produce more food using less water, and to do so without degrading soil and water resources. Drip irrigation technology can help meet this challenge by giving growers greater control over the application of water, fertilizers, and pesticides. Realizing the full potential of drip technology requires optimizing the operational parameters available to irrigators, such as the frequency and duration of irrigation, emitter discharge rate and spacing, and the placement of drip tubing. Numerical simulation is an efficient approach to investigating optimal drip management practices. However, there have been very few, if any, studies showing that numerical simulations of drip irrigation agree with field data, thus bringing into question the value of conclusions drawn from numerical simulations. The objective of this work was to compare HYDRUS-2D simulations of water infiltration and redistribution with field data, and to assess the utility of using simulation to design drip management practices. HYDRUS-2D is a well-known Windows-based computer software package for simulating water, heat, and/or solute movement in two-dimensional, variably saturated porous media. A Hanford sandy loam soil was irrigated using thin-walled drip tubing installed at a depth of 6 cm. Three trials (20, 40, and 60 L m-1 applied water) were carried out. At the end of each irrigation and approximately 24 hr later, the water content distribution in the soil was determined by gravimetric sampling. The HYDRUS-2D predictions of the water content distribution were found to be in very good agreement with the data. The results support the use of HYDRUS-2D as a tool for investigating and designing drip irrigation management practices.

Technical Abstract: Realizing the full potential of drip irrigation technology requires optimizing the operational parameters that are available to irrigators, such as the frequency, rate, and duration of water application, and the placement of drip tubing. Numerical simulation is a fast and inexpensive approach to studying optimal management practices. Unfortunately, little work has been done to investigate the accuracy of numerical simulations, leading some to question the usefulness of simulation as a research and design tool. In this study, we compare HYDRUS-2D simulations of drip irrigation with experimental data. A Hanford sandy loam soil was irrigated using thin-walled drip tubing installed at a depth of 6 cm. Three trials (20, 40, and 60 L m-1 applied water) were carried out. At the end of each irrigation and approximately 24 hr later, the water content distribution in the soil was determined by gravimetric sampling. The HYDRUS-2D predictions of the water content distribution are found to be in very good agreement with the data. The results support the use of HYDRUS-2D as a tool for investigating and designing drip irrigation management practices.