Quantifying naturalized streamflow entering Viet Nam from the upper Red River basin using the VIC-3L model

Tóm tắt

 The Red River Basin is an important transboundary river system, with the upstream area in China contributing substantially to water resources in Viet Nam. However, quantifying natural transboundary inflows remains challenging because of limited observations and increasing human impacts on water resources. This study applied the VIC-3L model to reconstruct naturalized streamflow in the main tributaries of the Red River Basin flowing into Viet Nam during 1981-2020. The model was calibrated and validated at the Muong Lay, Lao Cai, Dao Duc, and Bac Me stations using the SCE-UA optimization algorithm. Results show that the model accurately reproduced monthly streamflow, with Nash-Sutcliffe efficiency (NSE) values ranging from 0.91 to 0.95. Total annual runoff from the three upstream catchments in China (the Yuanjiang, Lixian, and Panlong rivers) decreased from 53.67 km³ during 1981-2004 to 48.14 km³ during 2005-2020, representing a decline of approximately 10.3%. At Lao Cai station, the naturalized streamflow was 19.62 km³/year, whereas the observed streamflow was only 13.07 km³/year, indicating a difference of about 6.55 km³/year. The larger reduction in observed streamflow compared with naturalized streamflow suggests that, in addition to reduced precipitation, upstream reservoir regulation, inter-basin water diversion, and water usage may have contributed to changes in streamflow entering Viet Nam. The study demonstrates the applicability of the VIC- 3L model for reconstructing naturalized streamflow and assessing transboundary water resources, providing a scientific basis for sustainable water resources management in the Red River Basin.