Effects of watershed management practices on the relationships among rainfall, runoff, and sediment delivery in the hilly-gully region of the Loess Plateau in China

- Watershed rainfall, runoff and sediment are investigated via nonparametric method.
- The runoff-sediment relations in similar watersheds are similar.
- Watershed management alters the runoff-sediment relation under critical low runoff.

The relationships among rainfall, runoff, and sediment delivery are significant in predicting soil erosion and in evaluating the benefits of watershed management practices (WMP) on the hilly-gully regions of the Loess Plateau. Hydrologic data (1987 to 2010) were analyzed for variations in precipitation, runoff, and sediment delivery at annual and event scale. These data were obtained from the Qiaozi East watershed (QE) and the Qiaozi West watershed (QW) with and without WMP, respectively. Results indicated that the runoff coefficients of the watersheds decreased significantly, although the runoff coefficient of QE was less than half of that of QW. Sediment delivery decreased more in QE than in QW mainly because of the increase in vegetation cover in both watersheds. In QE, the relationship between runoff and sediment delivery did not change significantly from 1987 to 2006, although the variation was significant from 2007 to 2010. In QW, the relationship between runoff and sediment delivery was not notably altered from 1987 to 2010. This finding suggested that vegetation practices and engineering measures on the hillslope did not strongly affect the relationship between runoff and sediment delivery in the watersheds. But the construction of check dams reduced gully erosion and the suspended sediment concentration. Hence, control practices for gully erosion significantly influenced the relationship between runoff and sediment delivery. This study suggests that a combination of hillslope and gully erosion control practices effectively reduces erosion and sediment delivery in the hilly-gully regions of the Loess Plateau.