Gangtok is facing a sharp decline in water availability as the perennial Ratey Chu source, the city’s primary supply line, has recorded close to a 60 percent depletion compared to September levels, according to Public Health Engineering (PHE) Secretary Shailendra Sharma. Citing an unprecedented dry winter from November to February with no significant rainfall, Sharma said the capital will now receive water supply only once a day, with revised timings to be announced shortly.
Field comparisons made by the department show that if September discharge is treated as 100 percent, current inflow into the system has dropped to about 40–45 percent. The two 350 mm (12-inch) transmission mains carrying water from Ratey Chu over a stretch of nearly 17 kilometres were designed to cater to the city’s admissible demand based on earlier population projections.
However, with discharge now reduced by more than half, the carrying capacity of the pipelines is no longer the limiting factor—the constraint is the reduced volume available at the source.
Gangtok’s distribution network is supported by more than 30 zonal storage tanks spread across elevations ranging from about 1,235 metres to nearly 1,972 metres above sea level.
These include high-level tanks such as VIP Tank (2.10 lakh litres), Old Selep Tank (4.10 lakh litres), Enchey ADB Tank (4.1 lakh litres), and Decheling Tank (0.06 lakh litres); mid-level reservoirs like the Press Tank (14.5 lakh litres), 3 Lakh Gallon Tank (13.0 lakh litres), Zero Point Tank (3.90 lakh litres), Sona Tank (3.90 lakh litres) and SNT Tank (2.50 lakh litres); and lower-belt tanks including Deorali Tank (2.5 lakh litres), Syari Tank (4.5 lakh litres), Chortain Tank (4.1 lakh litres), Housing Tank (2.5 lakh litres), Metro Tank (4.5 lakh litres) and New Metro Tank (3.2 lakh litres).
A cumulative assessment of the listed capacities indicates that the total designed storage across these reservoirs runs into several tens of lakh litres, with major tanks like the Press Tank and the 3 Lakh Gallon Tank forming critical balancing points in the system.
Under normal monsoon conditions, these tanks are filled close to capacity and enable twice-daily supply across zones. At present inflow levels, however, officials say storage cannot be maintained beyond roughly 30 percent on average. This effectively reduces usable buffer storage to less than one-third of its designed holding strength.
The imbalance becomes clearer when matched against demand. Gangtok has over 16,000 registered water connections. Even with a conservative estimate of five persons per household, the served population crosses 80,000 through domestic connections alone, excluding commercial establishments and floating populations.
Using standard urban design norms of around 135 litres per capita per day, the daily requirement would run into more than 10 million litres. With present discharge hovering at about 40–45 percent of peak monsoon availability, the system is operating at a substantial deficit, forcing a shift from two supply cycles to one.
Officials noted that infrastructure in several pockets—such as the Manipal Hospital and metro areas—was designed for a smaller resident base. Population growth, rental occupancy and migrant influx have increased consumption beyond the admissible design capacity of certain distribution lines. While the trunk mains remain 350 mm in diameter, several branch lines in lower belts were laid for limited household clusters, making equitable distribution more challenging under reduced inflow conditions.
Sharma said zonal timings are being recalibrated through trial-and-error optimisation, taking into account elevation, number of households and tank capacity. Even where a main tank is located in one locality, adjoining areas may receive water at different timings depending on gradient and pressure dynamics. The revised schedule will be made public shortly.
He urged residents to restrict usage strictly to drinking and essential domestic purposes. Commercial establishments have been advised to scale down consumption so that household supply is not compromised. The department has also begun inspections to check overflow from domestic tanks caused by faulty ball valves, warning that penalties can be imposed under the Water Supply provisions for repeated wastage.
While efforts have been made to maximise drawal from Ratey Chu, Sharma cautioned that extraction cannot exceed ecological limits, as it may affect aquatic flora and fauna. Snowfall this season has further reduced natural discharge instead of aiding recharge.
As a long-term corrective measure, an alternative water supply project drawing from the Bhusuk side is in an advanced stage and is expected to cater to Tadong and the lower belt, thereby reserving Ratey Chu water for higher elevations. The Asian Development Bank-supported project is likely to be tendered by March and completed within 24 months.
With seasonal rainfall patterns shifting, storage operating at barely one-third capacity, and consumption remaining constant despite nearly 60 percent source depletion, officials warn that March and April could prove more critical unless usage is reduced and recharge improves.
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