*Article* **Shallow Groundwater Responses to Rainfall Based on Correlation and Spectral Analyses in the Heilonggang Region, China**

**Chaoyue Wang 1,2,3, Fenggang Dai 1,2,3, Yang Liu 4, Yunmeng Wang 1,2,3, Hui Li 5,6 and Wenjing Qu 1,2,3,\***


**Abstract:** To clarify the long-term dynamics of groundwater and its response to precipitation in the Heilonggang region, China, variation trends of the monitored groundwater were studied according to the Mann–Kendall statistics. Based on observations from four monitoring wells, the persistence and periodicities of the loose porous aquifers, and the interrelation between precipitation and groundwater levels was examined based on a number of tools including autocorrelation, crosscorrelation, spectral analysis, and wavelet transform. The results show that the groundwater levels at W1 and W2 present a downward trend while those at W3 and W4 show an upward trend. The dominant time period increases from 2.1 years (upstream) to 3.7 years (downstream). The time lags between aquifers and rainfall at W1, W2, W3 and W4 are 139.14 ± 59.76 days (2008–2020), 23.27 ± 12.03 days (2005–2014), 145.01 ± 68.00 days (2007–2020), and 59.22 ± 26.14 days (2005–2019), respectively. The lags for the pumping years are 1.2~2.1 times of those during the years without pumping. The recharge ratio overestimated by the water table fluctuation method decreases from 0.32 at W2 to 0.17 at W4, suggesting that the site W2 has a good potentiality for groundwater recharge. This research helps us better understand the local groundwater circulation and provide references for groundwater management.

**Keywords:** groundwater; precipitation; correlation; spectral analyses; wavelet transform
