Spatiotemporal dynamics of groundwater recharge in Bangladesh

Understanding spatiotemporal groundwater recharge is vital for sustainable water management in Bangladesh, as anthropogenic and climatic factors severely strain available resources. Groundwater recharge in Bangladesh varies widely across its contrasting hydrogeological settings, yet their spatial and temporal dynamics and controlling factors remain insufficiently quantified. This study aims to quantify the spatial and temporal distribution of groundwater recharge across the western hydrogeological zones of Bangladesh and to assess the influence of land use and soil properties on recharge variability. The physically based, spatially distributed water-balance model WetSpass-M was applied to understand the spatial and temporal distribution of groundwater recharge and to examine the influence of geospatial and hydrometeorological parameters on recharge dynamics. Model results reveal a clear upstream–downstream recharge gradient, with persistently low recharge in the clay-dominated Barind uplands and moderate to high recharge in the coastal deltaic plains during the monsoon season. Temporally, recharge is strongly seasonal, occurring predominantly during the monsoon and closely tracking rainfall variability, with negligible dry-season recharge except in irrigated areas. Simulations also indicate declining recharge tendencies in the Barind region, whereas coastal recharge remains comparatively stable. Recharge patterns are strongly controlled by land use and soil properties. Forested and vegetated areas and loam to sandy-loam soils promote recharge, whereas built-up land and clay-rich deposits suppress infiltration. These findings highlight the dominant role of land-surface and subsurface properties in shaping recharge gradients. Future work will extend the analysis temporally and couple WetSpass-M simulated recharge with MODFLOW to support improved groundwater management and site-specific Managed Aquifer Recharge planning in drought- and salinity-prone regions.