Temporal Change in Runoff and Its Determinants in Upper Reach of Lijiang River Basin

Abstract

【Objective】 Climate change and anthropogenic activities have combined to change flow in many rivers and catchments in the world. This paper analyzes the change in runoff of the Lijiang Basin in southwestern China, as well as its determinants. 【Method】 The analysis was based on data measured from 1980—2019 from meteorological and hydrological stations along the Dayun river in the upstream of the basin. The temporal trend, abrupt changes and periodicity of the runoff, temperature and precipitation were analyzed using the Pettitt mutation test, Mann Kenddall test and Morlet wavelet analysis. The correlation between them was calculated using the multivariate linear regression equation. 【Result】 The runoff in the basin had been in decline though not at a significant level. There was an abrupt runoff change in 2018. From 1980 to 2019, the basin had experienced four drying - wetting cycles. The precipitation in the basin had been increasing and experienced an abrupt change in 2015. Approximately four periodicities were identified for the precipitation. The average annual temperature had increased significantly at 0.38 ℃/decade from 1980 to 2019, with an abrupt change occurring in 2016. There are two cold-warm cycles in the studied period, with 1984 and 2011 being the cold years, and 1981 and 2019 being the warm years. The period for temperature was 5~7 a. 【Conclusion】 Our analysis showed that the Lijiang basin will become increasingly dry. The basin will enter a warm stage in a 40- decade period. The abrupt change in runoff was due to the change in land usage, construction of flood control and water replenishment projects, climate change and other factors, while the abrupt change in precipitation and temperature is due to the climate change as experienced by other regions in South China.

Keywords

• runoff
• mutation test
• influencing factors
• periodicity
• lijiang river