[Baseflow variation and its response to precipitation in Jiuqushui watershed, Southern Jiangxi Province, China].

Baseflow is an important part of water resources. Exploring the characteristics of baseflow and its response to precipitation is of great significance to optimize the partition of water resources. Based on the data of daily precipitation and runoff from 1982 to 2019 in Jiuqushui watershed, we analyzed the characteristics of baseflow change, investigated the time lag effect of baseflow on precipitation, and calculated the contribution rate of precipitation to baseflow change by using digital filtering method, cross wavelet transform method, and slope change ratio of accumulative quantity method. The results showed that during the study period, the variation trend of annual baseflow depth and annual baseflow index was not significant, with annual average values of 384.21 mm and 0.44, respectively. The depth of baseflow in spring and summer was greater than that in autumn and winter, while the baseflow index showed an opposite pattern. Annual precipitation affected the dynamic change of annual baseflow depth, with the effects in spring and summer being stronger than that in autumn and winter. The lag time of baseflow in spring, summer, autumn and winter were 3.5-10.3, 1.5-8.5, 2-10, 2-13 and 5-20.5 days, while the average annual lag time was 6.4, 4.9, 5.3, 6.8 and 10.8 days, respectively. The annual baseflow depth changed abruptly in 1992. The contribution rate of precipitation to baseflow change was 68.2%, and that of other factors was 31.8%. The results could provide scientific basis for evaluating the hydrological effects of forests and ensuring water ecological security of rivers in the red soil region of southern China.