Resumen de Evaluation of drip irrigation: Selection of emitters and hydraulic characterization of trapezoidal units
Luis Juana, Leonor Rodríguez Sinobas, Raúl Sánchez Calvo, Alberto Losada Villasante
The primary focus of this paper is on the estimation of potential application efficiency in drip irrigation units. For this purpose, a new procedure for field evaluation of water distribution in trapezoidal drip irrigation units is proposed. It consists of measurement of flow discharged by a sample of emitters whose location in the unit is selected to assure that the sample has the same mean flow and the same flow variation as all the drippers in the unit. Several emitters at each location are considered to separate the variations due to manufacture and wear from those due to differences in pressure. As an additional aim, a simplified hydraulic analysis is proposed based on known expressions to characterize hydraulically the irrigation unit and also to separate the causes conditioning irrigation performance. This analysis requires data of the unit (lengths, diameters, spacings and elevations) and of the emitters (discharge equation exponent). In addition, variables such as inlet pressure head, total emitter flow, pressure heads at the downstream end of the submain and laterals, are also to be measured. These measurements are required to calibrate unknown parameters (emitter discharge coefficient, equivalent lengths of emitter or lateral insertion) to estimate their variation due to wear. Field evaluations were performance on rectangular and trapezoidal units. Emitters were selected following the proposed method as well as the one developed by Merriam and Keller [Merriam, J.L., Keller, J., 1978. Farm Irrigation System Evaluation: A Guide for Management. Utah State University]. Experimental results confirm the theoretical analysis. Finally, for practical purposes, an index and a unitary distribution curve of emitter discharge during irrigation are proposed to characterize the performance of level irrigation units, independently of their operating inlet pressure
