Hydrological and Participatory Evaluation of Ecological Integrity of the Ganges–Brahmaputra–Meghna Basin in Bangladesh

ABSTRACT Most of the rivers and waterbodies in the Ganges–Brahmaputra–Meghna basin in Bangladesh are continually losing ecological integrity due to low water flow and reduced connectivity. This research combines quantitative hydrological indicators with local knowledge to identify basin‐specific barriers and guide adaptive river and ecosystem management. The analysis focused on hydrological aspects, including trends in extreme river stage values, environmental flow (e‐flow) stages, seasonal fluctuations, connectivity and the impacts of hydraulic structures, using daily river stage data from 19 gauging stations collected between 1998 and 2017, along with qualitative data gathered through the participatory rural appraisal approach. For the e‐flow analysis, the dataset was divided into two periods (1998–2007 and 2008–2017) and categorized into yearly low‐flow, high‐flow and intermediate‐flow seasons. Most rivers exhibited significant declining trends, with annual stage fluctuations ranging from 1.3 to 12.3 m. The Little Jamuna River showed the highest river stage declines of up to 25.5 cm/year. About 80% of rivers failed to maintain e‐flow thresholds, with flow deficits ranging from 5% to 80% of days, indicating increasing ecological stress. Smaller rivers experienced sharper dry‐season declines and weaker connectivity than major rivers, primarily due to intensive irrigation, reduced upstream inflow and localized sedimentation. Water levels in the tidal Meghna River showed a slight upward trend, possibly in response to climate change–induced sea‐level rise. The study emphasizes the need for ecosystem‐based planning, improved regulator operations, rainwater harvesting, regulated groundwater abstraction and the reconnection of rivers to adjacent wetlands to restore ecological integrity.