An experimental study of unsaturated vertical infiltration based on sand samples from ephemeral streams

Unsaturated vertical infiltration tests were conducted based on sand samples from ephemeral streams to determine the main factors that may affect vertical infiltration. According to test results, the infiltration rate changes with time in 3 stages. Stage 1 is marked by a sharp descent; Stage 2 features a slow descent; and Stage 3 is characterized by a gradually steadied infiltration rate. The initial water content and texture of the sand samples have obvious influences on the infiltration rate. The vertical infiltration rate decreases with the increase of initial water content or dry density of sand samples, and increases with the increase of grain size. Coarse sand has a steadier infiltration rate than fine sand. The experimental results were analyzed and evaluated using soil water movement and potential theories.