Effect of Runoff Dynamic on Sediment and Nitrogen Losses in an Agricultural Watershed of the Southern Shaanxi Region, China

The southern Shaanxi region will become a water source area of the middle route of the South-to-North Water Diversion Project after 2014. However, there is little knowledge of water quality conditions in the region. Therefore, 12 rainfall events were monitored to investigate the effect of runoff dynamics on sediment and nitrogen (N) losses during the 2011 rainy season in the Hougou agricultural watershed. The results showed that at the seedling stage (SS), most of the rainfall contributed to an increase in the soil water content, both runoff and sediment yield were small, and there was a significant linear correlation between runoff and sediment yield (r=0.957, p<0.01). Despite an increase in vegetation coverage at the vigorous stage (VS), both runoff and sediment yield clearly increased with increasing rainfall, and there was a significant power function relationship between runoff and sediment yield (r=0.922, p<0.01). In addition, there was a significant linear correlation between runoff and sediment yield (r=0.981, p<0.01) at the harvest stage (HS). The best fit equations among N losses (N) and runoff (R), sediment yield (S) is N=aRbSc, and the method proposed was available to reduce relative error for calculation of N losses during the 2011 rainy season. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.