Closed loops, air cooling, liquid cooling and treated tertiary water: how Chennai data centres design past the 2019 water reset, and the records that verify a water position.
Heat rejection at data-centre scale historically leaned on evaporative cooling, whose water draw at tens of megawatts is industrial in volume. Chennai's 2019 crisis, when the city's reservoirs effectively emptied, made unhedged freshwater dependence an unbankable assumption: lenders, hyperscale tenants and the state all now scrutinise the water line of a campus design.
The good news is that the design space has moved: modern builds in water-conscious markets combine closed-loop systems, air-cooled chillers, and increasingly liquid-cooled IT with minimal make-up, trading some power efficiency for water independence.
The options ladder: open evaporative systems, maximum water, best historical PUE; closed-loop with adiabatic assist, modest make-up water concentrated in hot months; fully air-cooled chillers, near-zero water at a power-efficiency cost that Chennai's coastal climate moderates; and direct liquid cooling for AI-dense halls, which shifts heat capture into the rack and pairs well with closed loops. Treated tertiary water from metropolitan sewage-reuse schemes offers a non-potable make-up source that several Indian metros, Chennai included, are building out for industry.
The right answer is a portfolio: design-point analysis against Chennai's actual wet-bulb profile, water-price scenarios and the AI-era density roadmap, not a default copied from a temperate-market template.
Whatever the design draws, the supply position must be contractual and verified: metro-water industrial connections where available, treated-water offtake agreements with the relevant utility schemes, groundwater only with CGWA-compliant clearances and honest sustainable-yield assessment, and tanker dependence treated as contingency, never baseline. Discharge closes the loop legally: blowdown and reject streams meet TNPCB norms, with zero-liquid-discharge configurations increasingly specified.
Each element is documentary, connection sanctions, offtake contracts, clearances, consent conditions, and belongs in the site's diligence file alongside power and title.
Water strategy feeds back into the land question: proximity to treated-water infrastructure becomes a siting advantage; parcels with credible non-potable supply de-risk the design; and the TNPCB consent pathway for the chosen cooling configuration should be mapped before commitment. In our data-centre verification, the water layer is graded with the same rigour as power, because a campus that cannot cool is a campus that cannot run.
Chennai can absolutely host water-responsible hyperscale capacity; the operators winning here are the ones who engineered for the city they are actually in.
It ranges from industrial volumes for open evaporative designs to near zero for air-cooled and closed-loop configurations. Technology choice, not geography, sets the demand; modern Chennai builds design toward minimal freshwater draw.
Highly treated wastewater from metropolitan reuse schemes, supplied for non-potable industrial uses like cooling make-up. It decouples the campus from potable scarcity and is expanding in Chennai.
Supply-side: utility connection sanctions, treated-water offtake contracts and groundwater clearances where applicable. Discharge-side: TNPCB consent conditions on blowdown and reject streams, with ZLD increasingly specified.