Observation and Simulation of Runoff and Suspended Sediment Flux of the Mabengnong Catchment in Southeast Tibet

Various forms of soil erosion coexist in the Tibetan Plateau. The harsh climate condition make the land surface difficult to recover once destroyed. This study focuses on the hydrological and sediment processes in the plateau, to provide scientific basis for local soil and water conservation planning. The Mabengnong catchment in southeast Tibet was selected as the study area. Field monitoring of rainfall, runoff and suspended sediment concentration was carried out during 2012 and 2013. Based on the field observation data, distributed models were used to analyze the hydrological and soil erosion processes in the study area. The following conclusions were derived through the study: (1) rainfall data shows that rainfall recorded at the nearby Nyingchi weather station was significantly correlated with rainfall observed in the study area and thus average precipitation durations and precipitation gradients were derived for different precipitation grades, ie., trace rain, light rain and moderate rain using both the Nyingchi weather station data and field observation data. (2) using the WEB-DHM hydrological model for runoff simulation, the results show that rainfall gradient has a great influence on the simulation results. Runoff will be seriously underestimated without consideration of rainfall gradient. (3) using the WASH123D sediment transport model for sediment flux simulation, the results show that the summer runoff suspended sediment concentration is mainly influenced by precipitation. The soil erosion parameterization scheme confirms that erosion intensity is closely related to rainfall intensity.