Exploring groundwater dynamics through change point detection in static water level in the alluvial plain of Purba Bardhaman district, West Bengal, India

Static water level dynamics is an integral process of a complex hydrological system. However, the concern arises if the static water level goes beyond the long-term average level and the groundwater abstraction rate recurrently exceeds the recharge rate. The present study attempts to uncover the hydraulic head dynamics in the Purba Bardhhaman district based on the past 25 years of static water level data (1996-2020) retrieved from a web-based Water Resource Information System (WRIS) maintained by the Central Groundwater Board. Change year detection in static water level is an effective way to determine whether any monotonic increasing or decreasing trend persists in the static water level of the Purba Bardhhaman district. Multiple change year detection methods such as Pettit’s test, SNH homogeneity test and Buishand rang tests have been applied to determine the exact change year from which abrupt change in SWL was started. Descriptive statistics like average, standard deviation, change rate and coefficient of variation (CV) in SWL were performed before and after the change point. Variability in SWL has been determined using a graphical analysis and groundwater level index. The trend in SWL for both pre and post-change points has been identified using a simple linear regression model for selective wells in this area. The results revealed that most of the wells found a declining SWL in both the pre and post change point conditions. This study has considered and used a network of groundwater monitoring wells consisting of 47 wells. Additionally, a substantial negative trend was noted in the annual groundwater level.