Variations and trends of trans-boundary runoff in the longitudinal range-gorge region

The mountainous hydrological process usually shows high variation to climate change and human action. In the Longitudinal Range-Gorge Region (LRGR), Southwestern China and Southeast Asian, the transboundary runoff variations are much more sensitive and complex under the interaction of climate change, “corridor-barrier” functions in LRGR, and dams building. In this paper, based on the long hydrological records (1956-2013) from three mainstream hydrological stations in Nu River, Lancang River, and Red River, the region runoff variations were analyzed. The results show out: i) the regional runoff changes were strongly influenced by the “Corridor-Barrier” functions in LRGR from west to east, the variability extent of annual runoff increased, but tended to decrease after 2009 and the reduced extents also increased; ii) the annual runoff change in the three rivers had high concentration degrees; iii) there were periodicities of 33 years of runoff change in Nu River and Lancang River, and 30 years in Red River, and the lower flow period would continue for 8-9 years in Nu River and Lancang River but only for 4 years in Red River; iv) since 2010, as the two mega dams of Xiaowan and Nuozhadu built in Lancang River mainstream, their variations of annual runoff were quite different. The research results could offer a scientific base for sustainable utilization, conservation, and management of the regional water resources