Ahmedabad's 10,000 Buried Tankas Could Return to Service

Nearly 10,000 Tankas — underground rainwater storage chambers — may still exist beneath the domestic courtyards of Ahmedabad, according to a 2026 study published in Built Heritage. The survey behind the study also found that 90 percent of residents questioned expressed willingness to reintegrate Tanka water into the urban system.

The finding lands at a moment when Indian cities face water stress, seasonal rainfall and mounting pressure on municipal supply. Researchers and restoration efforts are now examining whether traditional water structures — stepwells, community wells and household Tankas — can function again as working infrastructure rather than photographed relics.

How the Tanka worked as a system

The Tanka was simple in construction but dependent on the whole house operating together. Rainwater was collected from roofs and courtyards, directed underground and stored within lime-lined chambers. The structures typically sat several meters below ground, built from stone, brick and lime mortar, with sloping bases that allowed sediment to be removed during cleaning.

Water storage was part of the house itself. The building became part of the catchment and storage system.

Ahmedabad's geology explains why. The historic Walled City sits over dense clay strata, with groundwater often deeper than 40 meters, making wells difficult to dig and maintain. Collecting rainwater close to where it fell offered an alternative in a dense urban fabric with little room for larger water structures. The courtyard became a catchment. The floor became a threshold to an underground reservoir.

More than 200 community wells were constructed within Ahmedabad's pols by the late nineteenth century. Only 14 of the 94 documented stepwells in greater Ahmedabad lie within the historic Walled City. In dense neighbourhoods, smaller wells and Tankas were often more practical than the monumental stepwells that dominate India's water heritage imagery.

What happened to these systems?

The expansion of piped municipal infrastructure and stormwater drainage gradually made household rainwater systems less necessary. The establishment of the Dudheshwar Water Works in 1892 marked part of the shift toward centralised supply. The Tanka remained physically present for generations even as water arrived through a municipal pipe rather than a monsoon roof.

The 2026 research found that some surviving Tankas remain in use, while others have deteriorated or been repurposed. Water quality varies, with some existing systems requiring treatment before water can safely be consumed.

What does restoration actually deliver?

Bansilalpet Stepwell in Hyderabad offers one test case. For decades, the seventeenth-century stepwell had effectively disappeared beneath a dump. Workers removed approximately 2,000 tonnes of debris, after which a freshwater source was identified around seven meters below ground. The restored well was reported to have a water-carrying capacity of approximately 2.2 million litres.

The restoration also addressed the surrounding precinct, adding rainwater-harvesting measures and infrastructure changes. Reports record the well's association with the water supply of Gandhi Hospital.

The evidence has limits. Bansilalpet does not yet show that restored stepwells can supply cities at scale. It demonstrates water recovery, storage capacity and a deliberate attempt to reconnect the site with water management — not a proven long-term contribution to Hyderabad's overall water balance.

Amritvarshini Vav in Ahmedabad is a distinct case. Built around 1723 within the Walled City, the stepwell has an unusual L-shaped plan and extends more than 15 metres below ground. The Ahmedabad Municipal Corporation records that the structure was recharged in 2004, bringing one of its original functions back into use.

Who maintains infrastructure beneath private homes?

The harder problem begins once the water starts flowing. A Tanka depended on more than its masonry chamber: seasonal cleaning, preparation of roofs and pipes, decisions about when to begin collecting rainwater, and knowledge of how to maintain the system.

Who maintains a privately owned Tanka if it contributes to a neighbourhood water system? Who tests the water? Who pays for repairs? How does a municipal authority regulate infrastructure located beneath private homes?

The researchers argue that the existing governance framework lacks mechanisms to incentivise citizen participation and heritage-based water reuse. They propose a model combining municipal capacity with community involvement, built on routines of cleaning, testing, maintenance and shared responsibility. Without those routines, restoring the masonry does not restore the water system.

Can heritage buildings work as water infrastructure?

Reusing a historic water structure also introduces change. Contemporary safety requirements, water-quality standards, public access and urban infrastructure rarely match historic conditions, so a restored structure may need to accommodate systems that did not exist when it was built.

The Bansilalpet restoration extended beyond the well into the surrounding public realm, and the site now functions both as a water structure and as a civic and heritage destination. Continued use, the source notes, can itself be part of a structure's survival.

The Tanka worked because the roof, courtyard, reservoir and routines of maintenance formed one system. Bringing it back into use depends on whether the buildings, institutions and communities around it can support that system again — a shift that would require coordination between architecture, water policy, municipal authorities and residents.