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You are here : eLibrary : IAHR World Congress Proceedings : 35th IAHR Congress - Chengdu (2013) : THEME 3 - WATER ENGINEERING AND CIVILIZATION : Experimental Derivation of the Empiric Equation to Calculate the Time Required for Wetting the Crop ...
Experimental Derivation of the Empiric Equation to Calculate the Time Required for Wetting the Crop Root Horizon (on Example of Soils in Ararat Valley, Armenia)
Author : Mihran Margaryan and Armine Simonyan
Demand for fresh water resources is increasing every year in many countries around the world, while its reserves are reduced as a result of anthropogenic influence. In the Republic of Armenia about 70 percent of fresh water resources (both surface and underground) are used for irrigation purposes, while in the same time, the loss of water in irrigation system amounts to 40 percent on average. Due to the inefficient use of irrigation water many land plots are left out of agriculture production, as the amount o f available water is simply not sufficient to keep all the plots productive. It is evident that such high level of water losses is caused by the widespread application of the surface irrigation method. In order to reduce water losses the new efficient irrigation methods should be applied. In international practice drip irrigation is the most efficient method of irrigation, especially when water resources are limited. This method can be widely introduced in the Ararat valley and especially in the areas with high water demand for irrigation, where huge losses of water are observed due to the soil types requiring excessive irrigation (in some areas irrigation norms grow by two times due to the specific soil types). Regularities of moisture movement in soil are described by the nonlinear partial differential equation of second order; however, its solution for some boundary and initial conditions is associated with certain complications. In order to solve these equations the finite difference method is currently in wide use, the essence of which lies in the fact that the elements of differential equation are replaced by the ratios of differences resulting in the system of difference equations, which is solved by numerical methods. However, this method does not allow observing the regularities of processes, which is necessary while solving problems related to regulation of water regimes. This paper discusses the analysis and results of the experiments carried out in laboratory conditions to define moisture movement in the soil. The gray semi-desert soil type that requires excessive amount of water (more than the specified irrigation normative) was used during the experiment. This type of soil is wide spread in the Ararat valley ? the main agricultural production zone of Armenia. As a result of the lysimeter experiments the numerical and visual data was obtained for 10, 20, 30, 40, 80, 90, and 120 minutes after the commencement of experiment. Special computer software and experimentally measured data were used to determine the regularities of variation of frontal\transition surface of moisturized soil. After mathematical computation of the experimental data, the dependencies of the parameters of the curves from watering period and respective numerical values were defined. Obtained empirical equation allows calculating the time required to wet the crop root horizon through application of drip irrigation method depending on the thickness of the crop root zone. Application of obtained formula for defining the proper watering period allows reducing the amount of water required for irrigation by 2-2.5 times.
File Size : 242,198 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 35th IAHR Congress - Chengdu (2013)
Date Published : 18/07/2016
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