Investigating the coherence of groundwater quality of a coastal aquifer and the hydroclimatic factors via remote sensing and wavelet analysis

ABSTRACT This study examined the factors that influence the groundwater quality (GWQ) of the Miandoab aquifer, located in the northwest of Iran. The study investigated the impact of climate change, anthropogenic activities, teleconnection, total water storage (TWS), and the area and level of the Urmia Lake on GWQ. To identify the relationship between TWS fluctuations and GWQ, the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) data were utilized. Landsat data were employed to calculate the normalized difference vegetation index and to determine the area of the Urmia Lake. Wavelet coherence, partial wavelet coherence (PWC), and multi-wavelet coherence (MWC) were used to assess the coherence in four distinct zones of the aquifer, distinguished via ensemble clustering. The obtained results indicated that the MWC of the anthropogenic activities and climate change contained higher coherence with GWQ compared to the MWC of the teleconnection parameters. Among teleconnection indices, the Pacific Decadal Oscillation showed higher coherence, of between 0.9 and 1, with GWQ. In addition, there is about 0.2–0.3 more coherence between the GWQ and the Urmia Lake area than the Urmia Lake level. Among the investigated factors, the coherence obtained via PWC, between GWQ and GRACE-FO data, exhibited higher coherence compared to other analyzed factors, with a coherence ranging between 0.8 and 1.