Water and sediment yield response to extreme rainfall events in a complex large river basin: A case study of the Yellow River Basin, China

A considerable variability in water and sediment induced by climate change was shown to have a significant impact on a comprehensive management of complex large river basins. In this study, a basin-scale model of the water and sediment yield was established through using the Soil and Water Assessment Tool (SWAT) to assess the spatio-temporal response of water and sediment in the Yellow River Basin to extreme rainfall events. Also, an additional set of reservoir regulation and water consumption modules was incorporated in the SWAT, then a task of model calibration and validation was done using discrete regional units and a basin-scale simulation of intensive human activities was successfully implemented. Two basic indices including precipitation concentration degree (PCD) and the spatial distribution of maximum precipitation were used to characterize extreme rainfall events. Several extreme rainfall scenarios were specified to investigate the response of water and sediment variations in this river basin. Our results show that (i) the accuracy of SWAT in predicting water and sediment yield in complex large river basins was apparently improved if taking intensive human activities into account; and (ii) it is shown that changes in slope water and sediment yield are broadly coherent with changes in extreme rainfall patterns in the Yellow River Basin, but there is a significant difference in the response of water and sediment yield to extreme rainfall events among different regions. Specifically, if the PCD was greater than 0.435, the slope sediment yield during the flood season in monitoring reaches from Toudaoguai to Tongguan is in excess of 128.57 t/ha, indicative of severe erosion. Annual river runoff and transported sediment was 52.5 billion m(3) and 443 million tons, respectively, at the Tongguan hydrological station. These results could be used a reference for identifying the characteristics and trends of temporal and spatial changes in water and sediment yield under extreme rainfall events, thereby assisting decision making.