Experimental study of the expansion of soil wetting fronts from a point source in heterogeneous sloping lands

This research intended to measure wetting front advancements (WFA) under various conditions using a physical model. Wetting front advance, along with its distribution in soils, is one of the important parameters in drip irrigation. It is influenced by many factors, including land slope, emitter discharge and soil texture. The effects of these factors were investigated by constructing a physical model with dimensions of 60 cm in width, 120 cm in height and 160 cm in length. The experiments were conducted using two heterogeneous soils, three land slopes (0, 10 and 20%), three emitter discharges (2, 4 and 8 L/h) and a constant volume of irrigation water (24 L). The results of the heterogeneous soils with three horizontal layers were also compared with those of three homogeneous soils (heavy, medium, and light textures). The results indicate that on sloping lands, the wetted area of the WFA downstream from the emitter was, on average, 20–62% greater than upstream from the emitter. With increases in land slope, the wetted depth under the emitter decreased by 3–18%. Also, when land slope changed from 0–10% and then again from 10–20%, the maximum radius of the wetting front increased, on average, by 32%, 44.8% and 77.5% for discharges of 2, 4 and 8 L/h, respectively.