Impact of the long-term precipitation and land use changes on runoff variations in a humid subtropical river basin of China

Study region: Liuxihe River Basin in Guangdong province, China.Study focus: Deciphering the runoff variation and its causes is crucial for catchment water management. The impacts of long-term precipitation aand land use change on the annual surface runoff were quantitatively analysed using various methods for the period of 1948-2019.New hydrological insights: We found that abrupt change occurred in 2009 for precipitation and 2003 for runoff, and the slope of precipitation-runoff cumulative curve changed after 2000 with an increase of-122 %. This indicated that human activities in the early 2000 s may have resulted in a marked increase of runoff in addition to precipitation. The dominant land use transfer was from croplands to constructed lands, most profoundly during 2000-2010. The multiple linear regression analysis indicated that the increase of precipitation and the cropland-to-constructed land transitions were nearly equally responsible for the runoff increase. In total, the long-term precipitation and major land use change explained-79 % of annual runoff variation. Furthermore, the effect of surface water area especially the pond area was discussed, and the negative linear relationship was found not statistically significant, but the impact of pond area ratio and its storage capacity on peak flow during rainstorms is worth further exploration towards flood mitigation, which can serve as an important and effective measure for nature-based management.