Temporal-spatial evolution of lagged response of runoff to rainfall in Karst drainage basin, Central Guizhou of China

Both runoff and rainfall do not happen at the same time and there is a certain lag in time. The length of lag time and lagged intensity are greatly affected by watershed storage capacity, which is related to the occurrence of droughts. To analyze the spatio-temporal evolution characteristics of rainfall-runoff in this study, lagged index (LI) is to be established based on 11 hydrological stations and 56 rainfall stations during the period 1965-2016 in the Central Guizhou of China (CGC). The results show that (1) the lagged response of runoff to rainfall in the CGC mainly shows the lag-3 period (lag-3 month), with the lagged area accounting for greater than 80%; (2) the spatio-temporal distribution difference of lagged intensity at different lagged periods is the lag-2 period/month (C-v = 0.62) < lag-1 period/month (C-v = 0.78) < lag-3 period/month (C-v = 0.82) = current period/month (C-v = 0.82); and (3) the lagged frequency mainly showed the medium frequency in the 1960s-1980s, with the lagged area 29.8-46.7%, and the medium-high frequency (49-59.4%) in the 1990s-2010s. These mean that the watershed lagged effect is the coupling result of four factors (i.e., rainfall, basin water storage, human activities, and lagged period). Thus, this study is to provide the theoretical basis for the drought monitoring and prediction in Karst drainage basin.