Exploring groundwater dynamics through change point detection in static water level in the alluvial plain ofPurbaBardhaman district

Static water level dynamics is an integral process of a complex hydrological system. However, the concern arisesifthe static waterlevel goes beyondthe long-term average level andthe groundwaterabstractionrate recurrently exceedsthe recharge rate. The present study attempts to uncover the hydraulic head dynamics in the Purba Bardhhaman districtbasedon the past 25 years of static water level data (1996-2020) retrieved from a web-based Water ResourceInformationSystem (WRIS) maintained by the Central Groundwater Board. Change year detection in staticwaterlevelisaneffectivewaytodeterminewhetheranymonotonicincreasingordecreasingtrendpersistsinthestaticwaterlevelofthePurbaBardhhamandistrict.MultiplechangeyeardetectionmethodssuchasPettit’stest,SNHhomogeneity test andBuishand rang tests have been applied to determine the exact change year from which abruptchange in SWL wasstarted. Descriptive statistics like average, standard deviation, change rate and coefficient ofvariation (CV) in SWLwere performed before and after the change point. Variability in SWL has been determinedusing a graphical analysisand groundwater level index. The trend in SWL for both pre and post-change points hasbeen identified using asimple linear regression model for selective wells in this area. The results revealed that mostof the wells found adeclining SWL in both the pre and post change point conditions. This study has consideredandusedanetworkofgroundwatermonitoringwellsconsistingof47wells.Additionally,asubstantialnegativetrendwasnoted inthe annualgroundwaterlevel.