Abstract
The most common methods for estimating the infiltration function are measurements through a double-ring infiltrometer (DRI) and empirical models. Infiltration data always exhibit different kinds of scatter, which affect the accuracy of the estimated infiltration function. This study presents a new methodology to calibrate the infiltration function. The suggested approach is based on combining the DRI method with the changes in the measured soil water content. Furrow irrigation experiments were conducted to estimate the infiltration function using different methods and to investigate the effect of data scatter on the reliability of the estimated infiltration function. Furrow elevations were observed, and for each irrigation event advance times, recession times, and inflow rates were observed. The infiltration depths were measured as a function of the change in the soil water content before and after irrigation event. Infiltration parameters were estimated using DRI treatment, empirical model (Kostiakov model), and suggested approach. Measured and simulated infiltration depths using the described methods were compared. The results show that the infiltration depths estimated using a DRI were lower than the observed infiltration depths, while the infiltration depths estimated using the empirical model were higher than the observed infiltration depths. The results indicate that the infiltration function estimated using the recommended approach was more accurate and reasonable than the infiltration function estimated using the DRI, and empirical (Kostiakov model) methods. In addition, the proposed approach can reduce the required measurements during the irrigation event, and can also reduce the potential scatter in the estimated infiltration function that results from soil variability and measurement errors.
Highlights
Soil infiltration characteristics are important for the evaluation, design and management of surface irrigation systems
The required data for infiltration determination always exhibit different kinds of scatter, which affect the accuracy of the estimated infiltration function
The approach depends on the estimation of the infiltration function using a combination of a double-ring infiltrometer (DRI) and soil water content measurements
Summary
Soil infiltration characteristics are important for the evaluation, design and management of surface irrigation systems. Many studies have been conducted to define coefficients in empirical infiltration models based on the volume balance approach (i.g., the two-point method [5,6,7,8,9,10], onepoint method [11,12,13], Saint-Venant approach [14, 15], zero-inertia approach [16,17,18], and kinematic-wave approach [18, 19]) These approaches depend on different levels of measurements, and errors in the measurement data can cause substantial errors in assessing the soil infiltration function [20]. In this case, the collection of a large amount of data (i.g., observations of the advance time, recession time, and soil water content every 5 m along the field length instead of at one-point or at two-points) can decrease the data accuracy, for large-scale projects when using laborers with imperfect knowledge about data collection [26,27,28]
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