Application of innovative trend analysis methodology to evaluate long-term spatial-temporal variations in groundwater fluctuations

Groundwater is the principal freshwater resource in drought-prone northwestern Bangladesh, supporting irrigated agriculture, domestic supply, and industrial use. This study examines long-term groundwater depth (GWD) dynamics in the Barind Tract region using a 37-year dataset (1985 -2022) from 37 monitoring wells across eight upazilas. The innovative trend analysis (ITA) method – an assumption-free, slope-based approach – is applied in this region to robustly quantify the direction and intensity of groundwater fluctuations under nonstationary conditions. Results reveal a widespread and statistically significant decline in groundwater levels, with nearly all wells showing consistent reductions in both annual maximum (pre-monsoon) and minimum (post-monsoon) GWDs. High-impact areas, including Nachole, Godagari, and Gomastapur, exhibit the steepest declines, with ITA slopes frequently exceeding 1.0. These trends are strongly associated with intensive groundwater abstraction for Boro rice cultivation, which accounts for approximately 87% of irrigated land, combined with insufficient monsoonal recharge due to declining rainfall and low-permeability surface clay layers. In contrast, relatively stable conditions occur near major river channels, where river -aquifer connectivity enhances recharge. The findings provide a quantitative basis for sustainable groundwater management aligned with the Bangladesh Delta Plan 2100 and the Sustainable Development Goals, emphasizing spatially targeted regulation, crop diversification, and artificial recharge interventions.