A J; M M; H E
Abstract
In management of surface irrigation, infiltration function is important. Quantitative understanding of this phenomenon is essential in preventing soil erosion and water losses. The main objective of this study was to estimate the coefficients of infiltration equations (Kostiakov-Lewis, Philip, and Horton) ...
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In management of surface irrigation, infiltration function is important. Quantitative understanding of this phenomenon is essential in preventing soil erosion and water losses. The main objective of this study was to estimate the coefficients of infiltration equations (Kostiakov-Lewis, Philip, and Horton) and evaluate the sensitivity and performance of these equations under various initial (initial soil moisture) and boundary conditions (water head on soil surface). Therefore, two-dimensional infiltration for furrow irrigation were simulated by changing the initial soil moisture (before irrigation) and water head on soil surface (during irrigation) using the solution of the Richards’ equation (HYDRUS model). To determine the coefficients of infiltration equations, outputs of the HYDRUS model (cumulative infiltration over time) were fitted. Evaluating the performance of infiltration equations via statistical evaluation indicators showed that infiltration empirical equations (Kostiakov-Lewis and Horton) had better performance than the physical equation (Philip) to estimate the cumulative infiltration under various initial and boundary conditions. Kostiakov-Lewis equation ranked the first in all cases of estimating infiltration by simulations, followed by Horton and Philip equations. Sensitivity assessment of the coefficients of the equations showed the power coefficient (b) of Kostiakov-Lewis equation as the most sensitive coefficient, while the final infiltration rate coefficient ( 15ff"> ) in Horton equation was the least sensitive. The results also showed that Horton equation was the most sensitive equation in evaluation of infiltration equations sensitivity.
A KHARAZMI; M MASHAL; GH ZAREI; M VARAVIPOUR
Abstract
The Guelph Permeameter technique (GP) is one of the proper methods for measuring the saturated hydraulic conductivity (Kfs) above the water table. This study was done by Guelph Permeameter model 2800k1 in 20 auger holes at Research Farm of Abourayhan Campus. Soil texture was determined for the Research ...
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The Guelph Permeameter technique (GP) is one of the proper methods for measuring the saturated hydraulic conductivity (Kfs) above the water table. This study was done by Guelph Permeameter model 2800k1 in 20 auger holes at Research Farm of Abourayhan Campus. Soil texture was determined for the Research Farm, using the hydrometer method. Water outlet flow of the permeameter was measured in four phases under constant ponding heads (H) of 5, 10, 15 and 20 cm, respectively. The field saturated hydraulic conductivity (Kfs) and matric flux potential (Øm), based on successful testing and Guelph analysis, were evaluated by different methods. The results indicated that, in heavy soils, increasing submergence depth of H2 relative to H1, is an appropriate solution for reducing the Guelph's two-head analysis failure in soil hydraulic conductivity estimation. In this study, well shape factor (C) was also calculated by five different methods. Later, the effect of the calculated C factor by various methods was studied in Guelph's two-head analysis. The results showed that using unsaturated effect in the calculations lowers the possibility of obtaining negative values of Kfs and Øm in Xiang Solution. Also, there was a very high correlation between Guelph successful two-head analysis when Xiang and Numeral Solutions were used for calculating C factor (r=0.98).