An assessment of oxbow lakes and their potential in reconstructing past river discharge: Implication to reconstruct past climate in Southern West Bengal

For modern fluvial systems, stage height, velocity, and cross-section help estimate a river’s discharge. However, understanding the amount and fluctuations of past discharges remains a challenge. The dimen-sions of the meander loops/oxbow lakes are directly proportional to the river’s discharge and the sedi-ment load type. Central West Bengal, India, has a complex network of numerous oxbow lakes as a rem-nant of the river Hooghly, a major distributary of the River Ganga. The present work revisits Schumm’s classic work to estimate river discharges from the meander loops and explores a potential proxy for es-timating past discharges. Thus, it is extended to reconstruct past climate using grain size data, facies analysis, and the dimension of the meander loops coupled with the luminescence chronology of oxbow lakes. The study reveals that the region received good rainfall during reported periods of intense mon-soon, and the increased discharge at different time intervals has given rise to numerous oxbow lakes. The discharge values have shown considerable fluctuations, rising to 15 to 20 times the current value and very few anomalously high, even up to 250 to 300 times, left unrecorded from other archives. The study shows the preservation of systematic growth of discharges and the meander loops with climate re-vealing events with anomalously high (and so highly disastrous) discharges at the scale of tens of thou-sands of years, usually missed from other archives. Results from Ichhamati and Hooghly River meander loops in West Bengal, India, indicate a manifold increase of discharges from the current during 1–1.5 ka (known as the Medieval Warm Period); around 2.2 ka and around 3.9 ka with low or gaps of enhanced monsoon, e.g., Little Ice Age and during 2.5–3.5 ka. This is an effort to show the potential of past mean-der loops to be explored well for comprehensive records.