Impact of Hydrological Modifications on Floodplains Wetland: Lower Atreyee River Basin of India and Bangladesh

This study explores how damming affects floodplain wetlandsFloodplain wetland in the lower Atreyee River basin (ARB) of India and Bangladesh. We analyzed hydrological shifts in both the river and its adjacent riparian wetlandRiparian wetland by examining three-hour interval discharge and water level data from 1993 to 2021. Our study specifically concentrated on the periods before and after the construction of a dam in 2012, encompassing pre-monsoon and post-monsoon seasons. To achieve this, we used a variety of methods to understand how damming affects water flow. These methods include box plots, heat maps, and wavelet transformationWavelet transformation. We also used the Normalized Difference Water IndexNormalized Difference Water Index (NDWI) was carried out to delineate the water bodies from satellite images of same phase. We checked the accuracy of our wetlandWetland maps using the Kappa coefficientKappa coefficient. Findings highlight significant differences from pre- to post-dam periods. After damming, the average water discharge decreased (70–168 m3/sec to 36–68 m3/sec). The variation in monsoonMonsoon flow also reduced, indicating a changed natural flow pattern. Discharge rates dropped significantly, and the flow pattern was altered after dam construction. Wavelet power spectrum analysis detected a prominent shift in flow variance after damming. Flow failure rates increased post-dam, especially during lean months. This reduction was due to water diversion through the dam and other extractions, leading to an ecological deficit. After damming, the wetlandWetland area decreased from 412.63 km2 in 2013 to 300.74 km2 in 2021, indicating a broader loss. Seasonal wetlandWetland areas decreased from 361.15 km2 (1991) to 62.58 km2 (2021). This study highlights the substantial ecological impact of damming, shown through changed flow dynamics and substantial wetlandWetland loss.