Abstract
Knowledge of infiltration characteristics is useful in hydrological studies of agricultural soils. Soil hydraulic parameters such as steady infiltration rate, sorptivity, and transmissivity can exhibit appreciable spatial variability. The main objectives of this study were to examine several mathematical models of infiltration and to analyze the spatial variability of observed final infiltration rate, estimated sorptivity and estimated transmissivity in flood spreading and control areas in Ilam province, Iran. The suitability of geostatistics to describe such spatial variability was assessed using data from 30 infiltration measurements sampled along three lines. The Horton model provided the most accurate simulation of infiltration considering all measurements and the Philip’s two-term model provided less accurate simulation. A comparison of the measured values and the estimated final infiltration rates showed that the Kostiakov-Lewis, Kostiakov, and SCS models could not estimate the final infiltration rate as well as Horton model. Estimated sorptivity and transmissivity parameters of the Philip’s two-term model and final infiltration rate had spatial structure, and were considered to be structural variables over the transect pattern. The Gaussian model provided the best-fit theoretical variogram for these three parameters. Variogram values ranged from 99 and 88 m for sorptivity and final infiltration rate to 686 (spherical) and 384 m (Gaussian) for transmissivity. Sorptivity, transmissivity and final infiltration attributes showed a high degree of spatial dependence, being 0.99, 0.81 and 1, respectively. Results showed that kriging could be used to predict the studied parameters in the study area.
Highlights
Evaluation of soil infiltration characteristics and knowledge of sorptivity and transmissivity can be useful for irrigation management
The lowest root mean squared error (RMSE) was obtained for the Horton model at most sites, demonstrating that the Horton model was the best-fit infiltration model for the entire study area
The values of the final steady infiltration and RMSE showed that the estimated infiltration rates by the Horton infiltration model were closer to the measured values at the selected flood spreading and control areas (Table 1 and 2)
Summary
Evaluation of soil infiltration characteristics and knowledge of sorptivity and transmissivity can be useful for irrigation management. Measurement of these parameters is time consuming; several empirical models (Kostiakov, 1932; Horton, 1940) and physical models (Green-Ampt, 1911; Philip, 1957) have been used for their estimation. Summaries of these mathematical models are provided by Philip (1969) and Ravi & Williams (1998). The ability of mathematical models to estimate infiltration rate was examined by Shukla et al (2003), Machiwal et al (2006), Haghighi et al (2010). Machiwal et al (2006) found that the infiltration process in wasteland in Kharagpur, India was welldescribed by Philip’s model (Philip, 1957). Haghighi et al (2010) showed that the Horton model (Horton, 1940) provided the best predictions of final infiltration rates in rangelands in the Taleghan watershed in Iran
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