Long-term geospatial assessment of land cover dynamics and surface-groundwater resources in Rajshahi City for sustainable urban management

Urban vegetation and water resources are the most vital components for maintaining ecological balance and ensuring environmental resilience in rapidly growing cities. This study focuses on Rajshahi, the greenest city in Bangladesh, with three primary objectives: (i) to analyze land cover and surface water dynamics, (ii) to assess spatiotemporal groundwater depletion, and (iii) to examine groundwater quality trends in relation to declining water tables. Multi-temporal Landsat imagery and long-term hydrological records (1990–2024), were used to evaluate urban landscape transitions and spatial groundwater levels status. Multidisciplinary approaches including image preprocessing, image classification, change detection, water indices calculation, spatial interpolation, and accuracy assessment were performed for sensible results. In addition, groundwater quality was assessed through in-situ measurements, major ion analysis via titration, and trace metal detection using UV spectrophotometry and atomic absorption spectrophotometry (AAS). Findings revealed a 543.56% increase in built-up areas, while vegetation and surface water bodies declined by 78.29% and 79.34%, respectively, over 34 years. During this time interval groundwater levels dropped by 6.38 m in pre-monsoon and 4.25 m in post-monsoon periods. Hydro-chemical analyses from 2010, 2017, and 2024 showed increasing concentrations of dissolved ions in groundwater, with very strong positive correlations (r ≈ 1) between water table decline and rising electrical conductivity (EC), total hardness (TH), and total dissolved solids (TDS) indicating worsening groundwater quality due to prolonged mineral interaction. However, this study provides critical evidence to support integrated urban planning and water resource policies for sustaining ecological integrity and managing future urban growth.