Abstract:

Snowmelt water is a significant component of spring runoff in the Lancang River basin, making it crucial to understand the variation of snow cover in the upper reaches of the Lancang River and accurately simulate snowmelt runoff processes for the scientific scheduling of water resources for cascade hydropower stations. Using remotely sensed snow cover data from 2000 to 2019, we applied the Mann-Kendall trend test to analyze the spatio-temporal variations of snow cover in the upper Lancang River basin and established a snowmelt runoff model (SRM) to simulate the snowmelt runoff process in 2018 and calibrated the model parameters using the Particle Swarm Optimization (PSO) algorithm. Results indicate that 1) Snow cover in the upper reaches of the Lancang River exhibited insignificant upward trend in spring, autumn, and winter, but an insignificant decline in summer. The average annual snow cover for spring, summer, autumn, and winter was 0.16, 0.06, 0.13, and 0.17, respectively. 2) Snow cover increased in the southwest and north of the Lancang River source area across all seasons, but decreased in the southeast. The northwest region experienced the largest increase in winter, reaching 3% per year. 3) The SRM demonstrated good applicability in the upper Lancang River basin, with coefficient of determination values reaching 0.87 and 0.78 for the calibration and verification periods, respectively, from January to May. These findings provide valuable insights for simulating snowmelt runoff in alpine regions.

Key words: upper reaches of Lancang River, snow coverage, Mann-Kendall trend test, Snowmelt Runoff Model, trend analysis, snowmelt runoff simulation