Wavelet analysis between groundwater level regimes and precipitation, North Pacific Index in the Xiongan New Area

Based on the time series data of four monitoring wells of groundwater level regime and precipitation in the Xiongan New Area, together with the North Pacific Index (NPI) from 1991 to 2016, periodicities of the time series and their relationships are analyzed in this paper by adopting methods of continuous wavelet transform and cross wavelet transform. The results show that (1) the main periods of the groundwater level regimes, precipitation, NPI and their resonance periods between each other are all 1a. (2) The lags of the rich precipitation period are all shorter than the lags of the whole time. Rich precipitation has greater influence on the lags of groundwater level regimes in unconfined-confined aquifers than those in confined aquifers. (3) The lags of groundwater level regimes to NPI are all longer than the lags of groundwater level regimes to precipitation. Responses of groundwater level regimes to NPI are faster in rich precipitation years, especially for groundwater level regimes in the unconfined-confined aquifers. The results reveal the time lag relationship of groundwater level regimes with respect to precipitation and NPI.