Ancient Tamil Nadu Lake Yields 4,500-Year Climate Record, Offering New Insights into Monsoons and Early Civilisation

The lake lies within an ancient settlement zone, making it uniquely suited to study how climate variability influenced water availability, ecosystems and human habitation.

 

A new scientific study has uncovered one of the most detailed long-term climate records from peninsular India, preserved beneath the sediments of Kondagai Lake near Sivaganga in Tamil Nadu, offering rare insights into monsoon variability, ecosystem change and human settlement over the past 4,500 years.

The research, conducted by scientists from the Birbal Sahni Institute of Palaeosciences (BSIP), Lucknow—an autonomous institute under the Department of Science and Technology (DST)—has been published in the international journal The Holocene.

Filling a Major Climate Data Gap in South India

Inland Tamil Nadu has very few well-dated, high-resolution lake records, despite being highly sensitive to the Northeast Monsoon. Recognising this gap, researchers focused on Kondagai Lake, located close to Keeladi, one of India’s most significant archaeological sites linked to a sophisticated urban civilisation of the Sangam period, possibly dating back to the 6th century BCE or earlier.

The lake lies within an ancient settlement zone, making it uniquely suited to study how climate variability influenced water availability, ecosystems and human habitation.

High-Resolution Climate Reconstruction

Researchers excavated a sediment profile just over one metre deep and analysed 32 closely spaced samples, each representing a distinct time slice. Using a multiproxy approach—including:

• Stable isotope analysis

• Pollen analysis

• Grain-size distribution

• Radiocarbon dating

they reconstructed past rainfall patterns, vegetation changes, lake levels and flood events with unusually high precision.

This represents the first high-resolution, multiproxy reconstruction of Late Holocene climate and lake ecosystem dynamics from inland Tamil Nadu.

Three Major Climate Phases Identified

The study identified three distinct climatic phases over the last 4,500 years:

• The 4.2 ka arid event, a globally recognised drought phase

• The 3.2 ka dry phase, marked by reduced monsoon strength

• The Roman Warm Period, associated with relatively wetter conditions

Crucially, the research establishes direct links between these phases and monsoon behaviour, lake hydrology and human activity in the Vaigai basin.

Implications for Climate Forecasting and Water Management

By reconstructing millennia of monsoon behaviour, the study provides a long-term climatic baseline that can strengthen regional climate models and help anticipate future droughts, floods and extreme rainfall in a climate-sensitive region like Tamil Nadu.

The findings are particularly relevant for drought-prone districts such as Sivaganga and Madurai, offering insights to support:

• Sustainable reservoir and tank restoration

• Groundwater recharge planning

• Climate-smart agricultural water use

Flood Risk and Disaster Preparedness

The identification of ancient flood deposits, terrestrial sediment influx and land destabilisation phases adds valuable information for risk mapping and disaster preparedness. Authorities can use these signals to identify areas vulnerable to flooding, river channel shifts and land degradation across the Vaigai river basin.

Benefits for Archaeology and Heritage Conservation

Located near the Keeladi archaeological complex, the environmental history of Kondagai Lake sheds light on how ancient societies adapted to climate stress, water scarcity and ecological change. This strengthens archaeological interpretation and supports heritage conservation and regional planning.

Guiding Ecological Restoration

From an ecological perspective, the study documents long-term changes in aquatic productivity, oxygen conditions and organic matter sources, providing a strong scientific foundation for wetland restoration, biodiversity conservation and lake management.

Researchers say the work demonstrates how natural archives hidden beneath small inland lakes can unlock critical knowledge about India’s climatic past—and help shape more resilient responses to its climatic future.

Publication: The HoloceneDOI: https://doi.org/10.1177/09596836251378011