Linking watershed hydrologic processes to connectivity indices on the Loess Plateau, China

Abstract

Sediment connectivity is an important property influencing landscape evolution. Understanding the link between sediment connectivity and hydrologic processes plays an important role in developing strategies for soil and water conservation measures. Based on 10 years of observations for 30 hydrologically monitored watersheds on the Loess Plateau, measurements for 926 hydrologic events were analyzed and the index of connectivity (IC) was calculated. The high-frequency runoff and sediment data were analyzed, and a normalized hysteresis index (HI) was calculated to assess the dominant hysteresis patterns for each watershed. Correlation analysis was conducted to determine the relationship between IC and HI. The results showed that the watersheds with low IC values were located in regions with dense vegetation and flat terrain and were dominated mainly by a clockwise hysteresis pattern, while the watersheds with high IC values were located in regions with sparse vegetation and steep terrain and were dominated by an anticlockwise hysteresis pattern. The anticlockwise hysteresis pattern was the most frequent and the most efficient type in terms of sediment transport among the 30 watersheds. The anticlockwise hysteresis type was more likely to occur as the IC values increased. A significant negative correlation was observed between the IC values and HI values during small and medium hydrologic events. The link is correlated with the notion that the separation into two components in connectivity indexes are similar to the two sediment sources controlling the hysteresis type. The outcomes from this study are helpful for determining the relationship between sediment connectivity and hydrologic behavior and thus for providing insight into the hydrologic processes that are essential to facilitate sustainable watershed management.