Total sediment transport from an urbanizing watershed in the upper Yellow River, China

For many event-based, high-sediment yield rivers draining arid zones, where erosion activities in the watershed and fluvial erosion in the stream channel are nearly equally important in sediment transport, determination of fluvial sediment dynamics are of great importance in establishing reliable strategies to manage environmental changes in watershed scale. Wash load rating curve indicating watershed characteristic changes and Ackers and White's bed load function (wash load excluded) used for determining bed load transport dynamics are distinguished for the first time to recognize the true sediment transport mode in the lower Huangshui River, which is the largest tributary of the upper Yellow River, contributing a lot to the wash load of the Inner Mongolia desert reach of the Yellow River and causing complicated water-sediment response. Based on the continuous and detailed hydrological data monitored at the Minhe gauge station, our results indicated that the sediment transport regime has altered since the 1980s in response to the eco-environmental changes mainly due to urbanization, with suspended sediment concentration (SSC) decreased by 50% on average compared with the natural state (1950-1980). The combined use of wash load rating curve and theoretical bed load function derived an estimate of total sediment transport due to comprehensive ecological management since the 2000s to be 3.43 × 107 t for the lower Huangshui River, among which the total bed load is 1.40 × 107 t, and the wash load is 2.03 × 107 t. The transport ratio of wash load to total bed load is 1.45:1.