EFFECTS OF FLOW DEPTH ON WATER FLOW AND SOLUTE TRANSPORT IN FURROW IRRIGATION: FIELD DATA ANALYSIS

Authors: ABBASI, FARIBORZ - ILWM, BELGIUM; Adamsen, Floyd; Hunsaker, Douglas - Doug; FEYEN, JAN - ILWM, BELGIUM; SHOUSE, PETER - USDA-RIVERSIDE, CA; VAN GENUCHTEN, M. TH. - USDA-RIVERSIDE, CA

Submitted to: Journal of Irrigation and Drainage Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2003
Publication Date: 6/9/2003
Citation: Abbasi, F., Adamsen, F.J., Hunsaker, D.J., Feyen, J., Shouse, P., Van Genuchten, M. Effects of flow depth on water flow and solute transport in furrow irrigation: field data analysis. Journal of Irrigation and Drainage Engineering. 129(4):237-246. July/Aug. 2003.

Interpretive Summary: A large number of commercial growers in the western States who use surface irrigation are injecting nitrogen fertilizers into irrigation water. This method of fertilizer application, 'fertigation', when used with surface irrigation can result in nitrate contamination of groundwater through deep percolation and surface water due to contamination of tail water. Because the environmental fate of nitrogen applied in surface irrigation water has not been studied extensively in the field, little information exists for establishing appropriate guidelines for this practice. A series of experiments were conducted at the University of Arizona's Maricopa Agricultural Center by researchers from the Catholic University of Leuven, Belgium, the U. S. Water Conservation Laboratory, Phoenix, Arizona, the U. S. Salinity Laboratory, Riverside, California, and the University of Arizona. The experiments evaluated a range of water depths and the duration of water application in level furrows. It was found that by increasing the depth of the water in the furrow the irrigation time can be shortened and the horizontal distribution of both water and solutes are improved. Improving the horizontal distribution of water and fertilizer reduces their depth of penetration into the soil which reduces the potential of groundwater contamination. These results should be useful to producers, consultants, irrigation design engineers, and other researchers.

Technical Abstract: Because of field-scale heterogeneity in soil hydraulic and solute transport properties, relatively large-scale experiments are now increasingly believed to be critical to better understand and predict the movement of water and dissolved solutes under field conditions. In this study, five field experiments were conducted on short blocked-end furrows to assess the effects of irrigation water level on water flow and solute transport in furrows. Three experiments were carried out, each of the same duration but with different amounts of water and solutes resulting from 6, 10, and 14 cm furrow water depths, designated as low, moderate, and high water levels, respectively. Two more experiments were performed with the same amounts of applied water and solute and, consequently, different durations, on furrows with depths of 6 and 10 cm of water. Results show that both the water level and the duration play an important role in transporting and distributing water and solutes in the soil profile. A positive correlation was found between water level and infiltrated amount of water or solute. Irrigation/solute application amounts increased with decreasing water level. Water and solutes were both distributed almost vertically one-dimensionally for the low water level and short application treatments, while they moved much more two-dimensionally with low and moderate water depths but longer application times. Irrigation with the 14 cm water level and short application time improved the distribution of water and solutes within the soil profiles, while also causing relatively less deep percolation of water and solutes as compared to low and moderate water levels and relatively long duration times.