Bakhira Lake sediments offer clues for better water-resource management in Central Ganga Plain
By- Jyoti Rawat
A new study of sediments from Bakhira Lake in Uttar Pradesh’s Sant Kabir Nagar district has reconstructed climate and monsoon variations over the past 25,000 years. The findings provide insights into how changes in climate influenced rainfall, weathering, sediment transport and lake processes in northern India.
The study could contribute to improving climate models for predicting future monsoon behaviour and support better water-resource management in the Central Ganga Plain (CGP), one of the regions most strongly influenced by the Indian Summer Monsoon and an important agricultural zone.
Long-term, high-resolution records of past climate from the Central Ganga Plain remain limited. Most earlier studies have relied on biological indicators or focused primarily on the Holocene period. To address this gap, researchers from the Birbal Sahni Institute of Palaeosciences (BSIP), an autonomous institute under the Department of Science and Technology (DST), examined environmental magnetic properties preserved in Bakhira Lake sediments.
The study shows that these magnetic properties can provide a continuous record of monsoon variability extending beyond the Holocene to the Last Glacial Maximum.
Bakhira Lake lies within the Ghaghara-Rapti alluvial system and is a perennial oxbow or floodplain wetland formed by the migration and subsequent cut-off of the Rapti River. One of the largest wetlands in Uttar Pradesh, it was designated a Ramsar Site in 2022.
Its floodplain-lacustrine setting allows sediments from both the lake and its surrounding catchment to accumulate and remain preserved. This makes the lake particularly sensitive to changes in monsoon-driven runoff, sediment transport and weathering.
The sediment sequence from Bakhira Lake extends back approximately 25,000 years and is supported by seven accelerator mass spectrometry (AMS) radiocarbon dates. This makes it a well-dated terrestrial archive for studying environmental and climatic changes during the Late Quaternary period in the Central Ganga Plain.
Environmental magnetic measurements can serve as useful indicators of past climatic and environmental conditions because they record changes in hydrology, erosion, sediment input and soil-forming processes. The well-preserved sediment sequence, along with other available geological and chemical data, provided the basis for the present study.
Researchers Nazakat Ali, Sajid Ali, Biswajeet Thakur and Anupam Sharma combined environmental magnetic measurements with grain-size, geochemical and clay-mineralogical records to reconstruct variations in the Indian Summer Monsoon from the Last Glacial Maximum to the present.
The sediment record captures several major climatic phases. These include the Last Glacial Maximum, when colder and drier conditions prevailed and the Indian Summer Monsoon was weaker; Heinrich Stadial 1 (about 25.3–18.1 thousand calibrated years before present), associated with cold and dry conditions; the Bølling-Allerød period (about 15.3–12.8 thousand years ago), marked by relatively warm and humid conditions and stronger monsoon activity; and the Younger Dryas (about 12.8–11.1 thousand years ago), when cooling, drying and weaker monsoon conditions returned.
The record also identifies the Holocene Climatic Optimum (about 9.2–4 thousand years ago), a relatively warm and wet period characterised by stronger monsoon precipitation and increased soil-forming activity. It also points to relatively dry conditions and reduced monsoon strength during the late Holocene, particularly between about 4,000 and 2,000 years ago.
Together, these findings demonstrate how major climate events affected rainfall, weathering, sediment transport and lake processes across northern India.
By combining seven AMS radiocarbon dates with multiple environmental magnetic parameters and previously published sedimentological and geochemical data from the same sediment core, the researchers developed a long-term reconstruction of Indian Summer Monsoon variability. Such records are particularly important in the context of present-day climate change and India’s dependence on monsoon rainfall for agriculture and water resources.
The research, published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology, also improves understanding of how the Indian Summer Monsoon responded to natural climate variations before the period of instrumental observations. Since direct climate measurements extend back only a limited period, scientists rely on natural archives such as lake sediments to reconstruct much older environmental conditions.
Long-term records of this kind can help distinguish natural climate variability from more recent changes associated with human activities. They also provide baseline information for improving climate models and assessing how river and lake systems may respond to changing rainfall patterns.
The findings could therefore have wider applications for water-resource planning, agriculture, flood and drought management and wetland conservation in the Ganga Plain, where millions of people depend heavily on monsoon rainfall.
Publication link: https://doi.org/10.1016/j.palaeo.2026.114028