|Hunsaker, Douglas - Doug|
Submitted to: Journal of Irrigation and Drainage Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2010
Publication Date: 6/20/2010
Citation: Perea, H., Strelkoff, T., Adamsen, F.J., Hunsaker, D.J., Clemmens, A.J. 2010. NONUNIFORM AND UNSTEADY SOLUTE TRANSPORT IN FURROW IRRRIGATION: I. MODEL DEVELOPMENT. Journal of Irrigation and Drainage Engineering. 135(5):537-555 Interpretive Summary: Fertigation is widely practiced by growers in the western United States as an efficient, cost effective, and flexible method of applying soluble fertilizers to irrigated croplands. Effective fertigation management practices in surface irrigation are vital for the economic and environmental sustainability of irrigated agriculture. The model developed in this study has the potential to help in the development of such practices. The management of salinity, another concern in irrigated arid lands, could similarly be improved. Potentially the model can evolve into a more comprehensive decision support system for fertilizer and salinity control in irrigated croplands. The immediate contribution of the reported work is that it represents an advance in solute transport modeling in surface irrigation. In a contribution to Science, the manuscript presents a furrow irrigation solute transport model that implements a more effective solution technique (split-operator approach) than in an earlier work on solute transport in irrigation furrows. Solute transport models, such as the one described, capable of predicting the distribution of fertilizer resulting from one or another operating procedure, can assist researchers, consultants, and action agencies such as the NRCS in evaluating strategies focused, for example, on timing fertilizer application in furrows. Developed guidelines could then be transmitted to irrigators and farm managers to maximize profits and minimize environmental damage.
Technical Abstract: A model for solving a cross-section-averaged Advection-Dispersion Equation (ADE) was developed to simulate the transport of fertilizer in furrow irrigation. The advection and dispersion processes were solved separately at each time step by implementing a method of characteristics with cubic spline interpolation and a time weighted finite difference scheme, respectively. The upstream boundary condition was a prescribed concentration. Downstream, a zero-flux boundary condition was prescribed during advance and a concentration gradient after advance. Local pseudo-steady state was assumed in order to apply Fischer’s longitudinal-dispersion equation under non-uniform and unsteady furrow flow conditions. Statistical parameters were used to evaluate model performance relative to analytic solutions. Evaluation under field conditions is described in companion papers.