Journal of Food, Agriculture and Environment

Measuring and estimating coordinates of wetted bulb front in soil under point surface emission

Author(s):

Ahad Molavi ^*, Amir Hossein Nazemi, Aliashraf Sadraddini, Ahmad Fakheri Fard

Recieved Date: 2010-11-02, Accepted Date: 2011-01-04

Abstract:

Trickle irrigation is one of the known techniques that can increase farm water use efficiency, provided that the emitter spacing, discharge and other hydraulic characteristics are designed properly. Knowledge about development of wetted bulb through soil can be involved in designing optimum arrangement of emitters and their flow rates. Correct usage of trickle irrigation system is a prerequisite for its progress and development, and perhaps wrong design leads to this conclusion that trickle irrigation is not an efficient system. In this study, coordinates of the developing wetting fronts through loam and sandy loam soils, resulting from surface drippers with inflow rates of 2 and 4 L h^-1 , were measured using trenching method and also those were predicted with respect to the Green-Ampt potential parameter, the Green-Ampt water content parameter, saturated hydraulic conductivity, radius of saturation part, and the reciprocal of the macroscopic capillary length scale, using Philip and Chu’s methods. Measured coordinates of the developing wetting fronts were compared to those predicted by Philip and Chu’s methods. The results showed that in most cases the solutions of Philip’s method were more accurate than those of Chu’s method, although solutions of the latter were also acceptable. The root mean square errors between the observations and results of Philip and Chu’s methods were 15.88 and 32.06 mm in loam and also 12.755 and 26.722 mm in sandy loam soils, respectively. Due to simplicity of the Chu’s method it is recommended as a suitable and applicable procedure. Final radii of the saturated zone were measured for different discharges of emitters indidually and on the basis of these discharges equations were obtained for the both loam and sandy loam using regression analysis.

Keywords:

Wetted bulb, wetting front coordinates, trenching, emitter

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Journal: Journal of Food, Agriculture and Environment
Year: 2011
Volume: 9
Issue: 1
Category: Environment
Pages: 505-509

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