Investigation to the relation between meteorological drought and hydrological drought in the upper Shaying River Basin using wavelet analysis

Investigation to the relation between meteorological drought and hydrological drought is important for facilitating early warning and mitigation of hydrological drought. Therefore, the propagation from the meteorological drought to hydrological drought in the upper Shaying River Basin, China was explored. Based on the goodness-of-fit test of monthly streamflow distribution from four hydrologic stations, the Pearson correlation analysis between monthly Standardized Precipitation Index accumulated periods of 1-24 months and monthly Standardizing Streamflow Index was applied to detect the propagation time between meteorological drought and hydrological drought; the continuous wavelet transform, cross wavelet transform, wavelet coherence and wavelet cross-correlation were utilized to depict the links between meteorological drought and hydrological drought in specific time-frequency bands. The results revealed: (1) different probability distributions were suitable for the Standardizing Streamflow Index at different gauging stations; (2) the propagation time from meteorological drought to hydrological drought notably varied with seasons, the longer in spring and winter and the shorter in summer and autumn; (3) hydrological drought and meteorological drought presented the similar patterns in term of phase shift; (4) close correlation existed between hydrological drought and meteorological drought with high absolute maximum and minimum wavelet cross-correlation coefficients, and changed with periodic scales and the lag time of hydrological drought to meteorological drought.