Effects of land uses and rainfall regimes on surface runoff and sediment yield in a nested watershed of the Loess Plateau, China

Abstract

Study region: The Loess Plateau, China. Study focus: Land-use and rainfall characteristics are two crucial influencing factors that affect the surface runoff and soil loss process; however, less attention has been paid to nested watersheds in vulnerable geo-ecosystems. Here we analyzed rainfall characteristics impacts on runoff and sediment in one of the nested watersheds, which contains six sub-watersheds with different land uses. According to rainfall amount, duration, and maximum rainfall intensity within 30 min (I30), 180 rainfall events during 2004–2019 were categorized into four types using K-means clustering method, and different hydrological years were distinguished. New hydrological insights for the study region: The runoff coefficient and sediment yield under the rainfall regime Ⅰ (little precipitation, moderate duration of precipitation, low intensity of precipitation) were the lowest; under the rainfall regime Ⅳ (high precipitation, short duration of precipitation, high intensity of precipitation), these values were the largest. The average runoff coefficient among the six sub-watersheds analyzed varied as follows: farmland watershed > farming-pastoral watershed > closed watershed > secondary forest watershed > mixed forest watershed > plantation watershed. The closed watershed had the lowest average sediment yield, while the farming-pastoral watershed showed the highest one. In addition, the runoff coefficient and sediment yield also changed differently in various hydrological years. The results of this study suggest that natural restoration measures are the optimal choice for coordinating the relationship between surface runoff and sediment yield. Enhanced long-term monitoring is needed to accurately describe watershed processes.

Keywords

• Land use
• Rainfall regime
• Surface runoff
• Soil loss
• Vegetation restoration
• Loess Plateau