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ABSTRACT
Studying the dimensions of soil wetting pattern (SWP) is important for designing optimal film hole irrigation (FHI) systems. HYDRUS-2D was used to simulate the dynamic changes of SWP under different soil texture (ST), initial moisture content (θi), film hole diameter (D) and irrigation water head (H) during FHI. The results indicate that ST and D, rather than H and θi, have a significant impact on SWP. Based on the simulation results, a power function was utilized to fit the horizontal radius (X) and vertical depth (Y) of SWP. The relationship between the fitting parameters and D, H, and saturated hydraulic conductivity (Ks) was analysed. An empirical model for estimating the X and Y was produced. Data from laboratory experiments and published studies were adopted to assess the empirical model. The results showed that the X and Y calculated using the empirical model were highly consistent with the observed data. The values of root-mean-square error vary from 0.355 to 1.107 cm and Nash Sutcliffe efficiency is closed to 1.0. In this study, the only parameter required for the empirical model is Ks, which can provide valuable and practical tools for FHI design.
Notations
| Ci | = | ith experimental calculated value of empirical model |
| D | = | Film hole diameter |
| H | = | Water depth above the plastic film |
| K(h) | = | Unsaturated hydraulic conductivity |
| Ks | = | Saturated hydraulic conductivity |
| N | = | Total number of values |
| NSE | = | Nash Sutcliffe efficiency |
| Oi | = | ith experimental observation value of empirical model |
| RMSE | = | Root mean square error |
| R2 | = | Coefficient of determination |
| Se | = | Effective degree of saturation |
| X | = | Wetted radius |
| Y | = | Wetted depth |
| a | = | Empirical coefficient |
| a1 | = | Fitting parameter |
| b | = | Empirical coefficient |
| b1 | = | Fitting parameter |
| b2 | = | Fitting parameter |
| c | = | Empirical coefficient |
| c1 | = | Fitting parameter |
| c2 | = | Fitting parameter |
| d | = | Empirical coefficient |
| d1 | = | Fitting parameter |
| d2 | = | Fitting parameter |
| d3 | = | Fitting parameter |
| d4 | = | Fitting parameter |
| h | = | Soil water pressure head |
| m | = | Empirical parameter |
| n | = | Empirical parameter |
| r | = | Radial (horizontal) coordinate |
| t | = | Time |
| z | = | Vertical coordinate |
| α | = | Empirical parameter |
| θ | = | Volumetric water content |
| θi | = | Initial water content |
| θr | = | Residual water contents |
| θs | = | Saturated water contents |
Disclosure statement
No potential conflict of interest was reported by the authors.