Uncovering soil preferential flow induced by different drip irrigation emitter settings: Insights integrating wetting-fronts image variability, HYDRUS-2D, and active region model

Abstract

Drip irrigation has gained widespread adoption in arid regions globally to counteract the water scarcity, yet the non-uniformity of soil water flow under drip irrigation remains inadequately understood. This study presented an indoor infiltration experiment with two soil types (sandy loam and sandy), three emitter sapcing (10 cm, 20 cm, and 30 cm), and two discharge rates (3 L/h and 4 L/h). We analyzed wetting front image variability, using HYDRUS-2D to interpret fractal parameters in active region model during infiltration. Initially, the wetting front was unstable, with a preferential flow ratio dropping from 90 % to 20 % and a variation coefficient decreasing from approximately 2 to below 1 across both soil types. The preferential pathways were found forming in a finger shape ways. Fractal parameters peaked at 15–30 min in sandy loam and 5–10 min in sandy soils, reflecting this instability. HYDRUS-2D data confirmed the non-uniformity indicated by the active region model, showing reduced fractal parameters with wider emitter spacing in sandy soils and an increase with larger spacing in sandy loam. Moreover, the principal component analysis identified optimal irrigation parameters: a 20 cm spacing with a 4 L/h discharge for sandy loam and a 40 cm spacing with the same discharge for sandy soils. Our research confirmed the presence of soil preferential flow even under drip irrigation and developed a new evaluation framework to assess the effectiveness of various drip irrigation parameters, considering soil preferential flow. This research offers new insights into optimizing drip irrigation in arid regions, enhancing water management in these areas.