Monsoon control of effective discharge, Yunnan and Tibet

Analysis of suspended sediment transport data for rivers in Yunnan and Tibet shows that monsoon flows control effective discharge. We calculate effective discharge, defined as the discharge that transports the most sediment, for 44 stations for which there is at least one complete year of daily suspended sediment concentration and mean daily discharge data, and find that the effective discharge is approximately the mean monsoon discharge for all stations. The correspondence of the effective discharges with the mean annual flow and monsoon discharge for all stations demonstrates that monsoon flow dominates suspended sediment transport in the region, rather than storm flow during discrete, short-duration storm events. In this region, the monsoon lasts for 4 months (June–September) and during that time transports 86% of the suspended sediment load. In contrast to the general observation from temperate environments that infrequent, stochastic storm events dominate sediment transport (with 90% of the suspended sediment transport occurring in 10% of the time), our findings show that the mean monsoon discharge dominates sediment transport in the rivers draining the southeastern Tibetan Plateau