Application of multiple approaches to investigate hydraulic connection in multiple aquifers system in coalfield

•We investigated aquifer hydraulic connection in coalfiled by different methods;•The impact of mine drainage on the hydraulic connection between aquifers was explored.•Time series analysis show consist result with hydrochemical and isotopic analysis. Understanding the hydraulic connections between overburden aquifers is key to safe coal mining. However, accurately identifying such connections remains challenging. Conventional investigation methods include geophysical investigation, pumping test, and hydrochemical analysis, which are time-consuming, expensive, and cannot determine continuous variations in hydraulic connection. In this paper, we performed time series analysis for analyzing water level time series data to identify the hydraulic connections between overburden aquifers in a coalfield. The proposed method can identify such connections more clearly than hydrochemical methods. It is especially useful in areas where an aquifer system is subject to strong perturbations.