Variations in Hotan riverbed permeability and seepage water amount by soil grain size changes from upstream to downstream

Severe seepage presents a significant challenge to the sustainable management of water resources, and a lack of seepage data from the upper, middle, and lower reaches of the Hotan River hinders effective resource management. This study assessed the water infiltration rate in the riverbed using the double-ring method and evaluated the performance of four commonly used infiltration models. Results showed that infiltration rates were highest in the upper section, with permeability decreasing towards the banks. Water consumption, seepage volume, and seepage per unit river length decreased from upstream to downstream. Specifically, seepage volumes were greatest in the upstream section, followed by midstream and downstream. The seepage rate per unit riverbed was highest in the upstream section, followed by the midstream, and lowest in the downstream section. The mean sediment volume fractal dimension was 1.34, positively correlated with sand content, while higher clay and silt content resulted in finer textures and smaller fractal dimensions. These findings fill critical gaps in understanding water infiltration patterns and sediment characteristics in the Hotan River basin, providing essential data for water resource management and ecological protection. Among the models tested, the Kostiakov equation outperformed the Philip, Green-Ampt and Horton models in terms of accuracy and applicability.