Effects of rainfall, sediment source–sink landscape, and hydrological connectivity on runoff more than sediment in a karst basin

Abstract

AbstractUnderstanding the mechanisms underlying soil and water loss in karst basins is beneficial for water resources management and soil and water loss conservation. However, the effects of rainfall, sediment source–sink landscape, and hydrological connectivity on runoff sediment characteristics in karst basins are unclear. This study used sediment source–sink landscape and hydrological connectivity theories and a generalized additive model to analyze the changes and combined effects of sediment source–sink landscape patterns, hydrological connectivity, and rainfall on runoff sediment from 2000 to 2020 in the Yeji River basin in the karst region of southwest China. The results indicated that the average sediment transport modulus and runoff modulus in the Yeji River basin during 2000–2020 were 144 t·km−2·a−1 and 15 L·s−1·km−2, respectively. The karst surface and subsurface double‐layer hydrological structure resulted in a lower sediment transport modulus than in non‐karst areas. The sediment‐source landscape area decreased, sediment‐sink landscape area increased, and sediment source–sink landscape load ratio index slightly increased. Hydrological connectivity exhibited a decreasing trend over time, but the overall change was small. Changes in source–sink landscape patterns significantly affected hydrological connectivity. As the main affecting factor, rainfall and its combined effects with sediment source–sink landscape patterns and hydrological connectivity explained 85% and 95% of the variances in runoff, and 40% and 63% of the variances in sediment, respectively. These results suggest that a rational layout of the sediment source–sink landscape can effectively improve hydrological connectivity and regulate the soil and water loss process. Our findings have important implications for karst basin ecological restoration and protection.