Abstract
Infiltration parameters and Manning’s roughness are essential input parameters for surface irrigation simulation models. Multiple points of infiltration experiments require time-consuming, costly data collection and problematic calculations of field mean infiltration parameters. This study estimated the field mean infiltration parameters and Manning’s roughness values on a regional scale, on the basis of closed-end furrow irrigation experiments conducted at 45 experimental sites on the Guanzhong plain, and evaluated the influence of Manning’s roughness on advance trajectory and performance indicators of closed-end furrow irrigation. Then, we present a functional normalization of the Kostiakov equation and pedotransfer function (PTF) to estimate the normalization factors. The proposed method can be used to estimate the field mean infiltration parameters using PTF and the represented Manning’s roughness to determine the optimal discharge of closed-end furrow irrigation. The results revealed that the advance trajectory and performance of closed-end furrow irrigation was not sensitive to variations of Manning’s roughness, which can be adopted as a representative value (i.e., 0.075) of the maize field. The normalization method was proven to be feasible for the Kostiakov equation, and the PTF reliably estimated the normalization factors. Last, the optimized values of the inflow discharge were determined using the proposed method, with various combinations of furrow lengths and bottom slopes in the study area, and also compared with the inflow discharge determined based on infiltration parameters and Manning’s roughness, which were inversed by SIPAR_ID. The results indicated that the inflow discharge values obtained through using the two methods were approximately equal, proving that the proposed method was reliable and easy to use in practice.
Highlights
Furrow irrigation is a widely used irrigation method, and closed-end furrow irrigation is one of its main variants
The reasons were that the cross-sectional area varied with different inflow discharges, and that the variability of soil characteristics at the field scale caused differences in field mean infiltration parameters and Manning’s roughness values for each experimental site
The accuracy of estimation depended on the accuracy of the data regarding upstream water depth; SIPAR_ID was used to estimate the field mean infiltration parameters and Manning’s roughness
Summary
Furrow irrigation is a widely used irrigation method, and closed-end furrow irrigation is one of its main variants. Furrow irrigation systems are often inefficient because of poor irrigation performance [1,2]. Advanced simulation models of surface irrigation have been proven to be effective for evaluating system design and management, and for improving irrigation performance. Manning’s roughness and field mean infiltration parameters are essential input parameters for surface irrigation. It is vital to obtain realistic estimates of Manning’s roughness and field mean infiltration parameters. In the actual surface irrigation process, numerous factors affect Manning’s roughness, and Manning’s roughness cannot be measured; the determination of Manning’s roughness is difficult, and wide ranges of variation have been reported [7,8]. Chow [9] reported Manning’s roughness values ranging from 0.02 to 0.40 for cultivated soils with no crop. Li and Zhang [10] determined that
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