Dimensional Analysis and Model Development of the Soil Wetting Pattern under Pulse and Continuous Drip Irrigation

Abstract

Challenges in continuous drip irrigation systems in Gujarat, India, include emitter clogging due to narrow water passages and low discharge rates. In sandy soils, the wetting depth becomes much greater than the width, resulting in excessive deep percolation beyond the crop root zone. To address these issues, widening the wetted area using high-discharge emitters is necessary, which supports the use of pulse drip irrigation. Since understanding wetted depth and width is essential for proper drip system design, the lack of models for predicting wetting patterns under pulse and intermittent flow—beyond those developed for continuous flow—creates a significant gap. Therefore, this study aimed to develop a dimensional analysis model capable of estimating the wetted zone geometry across continuous, intermittent, and pulsed flow conditions. A semi-empirical dimensional analysis approach was used to construct the model, and its predicted wetted depths and widths were compared with field observations. Experiments measured maximum wetting dimensions at 30, 60, and 120 minutes under different discharge rates (2, 4, and 8 LPH). Model performance was evaluated using root mean square error, mean error, and model efficiency, all of which indicated strong predictive accuracy. The results confirmed that the models can reliably estimate wetting patterns across all three irrigation regimes. Under pulse flow, reducing the operating duration for the same water volume increased horizontal spread while decreasing vertical penetration. Increasing pulse frequency (one to four pulses) further reduced deep percolation and enhanced lateral wetting, demonstrating the advantages of pulse irrigation in minimizing water loss while allowing the use of high-discharge emitters. The dimensional analysis models developed in this study effectively predicted wetted depth and width under continuous, intermittent, and pulsed line-source irrigation. Validation against controlled laboratory data showed strong performance, with efficiencies of 98% and 97% for depth and width under continuous flow, 94% and 83% under intermittent flow, and 86% and 79% under pulsed flow. These results confirm that the models reliably represent wetting behavior across different irrigation regimes and are suitable for predicting wetting patterns in line-source applications.