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Empires that rose and fell in the Deccan, or the southern part of the Indian subcontinent, knew about the vagaries of the Indian monsoon and its effects on societal, economic, and political situations, a new study has suggested.
These polities — from the Mauryans and Satavahanas to the Kakatiyas and Vijayanagar — consequently constructed water retention structures such as dams, anicuts, tanks and wells, as is well-evidenced from references on inscriptions.
The study urged revitalising traditional water retention features, such as tanks and ponds, as they are crucial for addressing contemporary water scarcity in India.
“These ancient structures offer sustainable solutions for groundwater recharge and irrigation, benefiting both rural and urban communities and ensuring a more resilient future in the face of climate change,” the paper noted.
The researchers wanted to understand the connection between past monsoon variations, water retention features, and the response of ancient communities. This, they said, is crucial for sustainable development amid climate change.
They developed “a near-annually resolved high-resolution terrestrial monsoon proxy record using stalagmites from Kadapa Cave, Deccan India, covering the last three millennia”.
The scientists did this by zeroing in on speleothems. These are mineral deposits that form in caves over time and are made up of calcium carbonate.
Speleothems capture terrestrial paleoclimate records, reflect rainfall variation in the tropics through changes in stable oxygen isotopes. These isotopic changes indicate variations in cave temperature and rainfall.
“Past monsoon rainfall changes have been reconstructed using oxygen isotopic values of Indian speleothems, where low and high values indicate wetter and drier monsoon conditions, respectively. A 1-1.5‰ variation in oxygen isotopes typically corresponds to an 86–100 mm change in rainfall,” the paper read.
Using δ18O data from the two cave stalagmites in Kadapa, Andhra Pradesh, the experts examined the relationship between past summer monsoon rainfall variations, ancient settlement patterns, and water retention features over the last three millennia.
The Z-scores of oxygen isotopic values were calculated to interpret wet and dry monsoon phases relative to ancient communities and kingdoms. Normalised oxygen isotope anomalies larger than+1 and less than−1 were identified as droughts and floods, respectively.
Settlement data and radiocarbon aging from important archaeological sites in the region were analysed to understand the relationship between monsoon variations and water storage features.
Prominent archaeological sites were examined to correlate settlement patterns with monsoon variations.
The paper offers interesting insights into how each polity that ruled the Deccan, responded to the challenge of conserving water.
For instance, the Mauryan Empire (322 BCE -185 BCE) established the first hydraulic civilisation, coinciding with a nearly century-long drought in the Indian mainland.
“Varahamihira’s Brihat-Samhita mentions tank construction and artificial irrigation. The Mauryans demonstrated a profound understanding of water balance, rainfall measurement, and hydrological processes, implementing water pricing systems, constructing dams with spillways, reservoirs, and channels. The well-maintained lift irrigation system of the Mauryan times was highly effective. Inscriptions from the Nashik cave and Mathura describe the construction of tanks and reservoirs post-Mauryan era,” the researchers noted.
The empire’s decline in the Deccan (particularly in southern Andhra Pradesh and Karnataka), resulted from interrelated factors.
The Mauryans recognised the importance of irrigation. However, uncertainties in land settlement and tax collection led to administrative inefficiencies, internal conflicts, and loss of control over distant provinces, contributed to the empire’s decline. Additionally, severe climate stress and inadequate land and irrigation policies played a role.
The Satavahanas (c. 228 BCE–c. 224 CE), who came after the Mauryans, used waterwheels for irrigation, an advancement from the Mauryan period. “Monsoon decline and drought conditions might have contributed to the Satavahana dynasty’s decline from the second to the mid-third century CE,” the paper notes.
Other great empires in the region that followed were even more specific in their emphasis on water and irrigation: The Pallavas, Cholas and Chalukyas.
“By the end of the 1st millennium BCE, the Satavahana empire declined, and the era of the Pallavans began. This period is credited with an increase in the number of tank constructions,” as per the paper.
It added: “The Chola kings (850–1200 CE) ruled over Tamil Nadu, Kerala, parts of Karnataka, and Andhra Pradesh, renowned for their emphasis on building numerous tanks and temples. From the mid-sixth to the eleventh century, the Chalukyas of Badami and Kalyani constructed canals, tanks, and reservoirs, especially during frequent droughts.”
Even smaller, lesser-known kingdoms and polities like the Ikshvaku kings (builders of Nagarjunakonda) and the Kadambas were known for their emphasis on waterworks such as canals and tanks.
The Hoysalas and Warangal’s Kakatiyas, who came much later, built tanks, embankments and other waterworks during their respective reigns.
“During the zenith of the Vijayanagara Empire, which encompassed the entire region south of the Tungabhadra and Krishna rivers, including present-day Karnataka, Andhra Pradesh, Tamil Nadu, and Kerala, the rulers placed signifcant importance on constructing tanks, wells, and vast reservoirs. They actively promoted agriculture by providing irrigation facilities through land reclamation and constructing tanks on these lands. Additionally, the Vijayanagara kings transformed valleys into extensive tanks for enhanced irrigation capabilities,” the paper stated.
The Bahamani kingdom, a rival of Vijayanagar which later broke into five Sultanates (Ahmadnagar, Bijapur, Golconda, Bidar and Berar), meanwhile invested in the karez system, also found in other Muslim lands.
“Historical records also document the establishment of ‘karez’ systems in regions like Bidar, Gulbarga, Bijapur, and Burhanpur by Bahmani rulers during the fourteenth century,” noted the paper.
“While present-day hydrological technology, such as major dams, is crucial for advancing agriculture, small-scale irrigation features like tanks and wells, known to be adopted by medieval kingdom rulers, can significantly mitigate severe drought or famine,” it added.
The extreme monsoon climate and associated ancient communities, kingdoms, irrigational advancement in Deccan India during the late Holocene was published in November 2024 in the journal Regional Environmental Change.
The authors of the paper are Annapureddy Phanindra Reddy; Naveen Gandhi; Siva Kumar Challa; Narayana Jangari and Chuan‐Chou Shen.
The authors are affiliated to institutions including Center for Climate Change Research, Indian Institute of Tropical Meteorology, Pune; High-Precision Mass Spectrometry and Environment Change Laboratory (HISPEC), Department of Geosciences, National Taiwan University, Taiwan; Department of History & Archaeology, Yogi Vemana University, Kadapa; and Research Center for Future Earth, National Taiwan University, Taiwan
