Document Type : Original Article
Authors
1
Department of Water Science and Engineering, Faculty of Agriculture, University of Kurdistan, Sanandaj, Iran.
2
Department of Water Science and Engineering, Faculty of Agriculture, Bu-Ali Sina University, Hamedan, Iran.
3
Department of Water Science and Engineering, Faculty of Agriculture, University of Kurdistan, Kurdistan, Iran. Department of Water Science and Engineering, Faculty of Agriculture, University of Kurdistan, Kurdistan,
4
Department of Water Sciences and Engineering, Faculty of Agriculture , University of Kurdistan. Kurdistan. Iran.
Abstract
Objective This study develops and evaluates models to simulate moisture distribution in two-layer soils under surface drip irrigation to improve optimal irrigation system design.
Method: A transparent physical model made of plexiglass was used to conduct the experiments. Six two-layer soil profiles were tested: L1 (medium–heavy), L2 (medium–light), L3 (heavy–medium), L4 (heavy–light), L5 (light–medium), and L6 (light–heavy). Nonlinear regression models were developed considering the hydraulic properties of the soil and the operational characteristics of the emitters to simulate moisture movement in both horizontal and vertical directions.
Results: A comparison of statistical parameters between measured and simulated data showed that the proposed models performed with high accuracy in simulating the initial moisture distribution phase, with correlation coefficients of 0.85 and 0.88 for the horizontal and vertical directions, respectively. However, during the redistribution phase, particularly in the horizontal direction, model accuracy declined slightly (correlation coefficients of 0.52 and 0.79). The root-mean-square error (RMSE) for predicting moisture distribution was 5.93 cm (horizontal) and 4.66 cm (vertical), and for redistribution was estimated at 8.87 cm and 8.03 cm, respectively. Additionally, the models showed a tendency to overestimate values in the horizontal direction and underestimate them in the vertical direction.
Conclusions: The proposed models demonstrated acceptable accuracy in simulating moisture distribution patterns in two-layer soils under drip irrigation. However, reduced accuracy during the redistribution phase—particularly in the horizontal direction—and the observed tendencies toward overestimation and underestimation indicate the presence of systematic errors in the modeling approach. Identifying and correcting these errors can significantly enhance the predictive capability of the models.
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