São Paulo's main reservoir system, Cantareira, saw a 0.1% drop in stored volume on January 1, 2026, reaching 20.1%, despite recent rains. This triggered the 'restriction' level, capping water withdrawals at 23 cubic meters per second, supplemented by the Rio Paraíba do Sul. Officials state there is no immediate risk of water rationing.
São Paulo's Cantareira System, supplying much of the metropolitan area, started 2026 on a concerning note. On January 1, its useful volume dropped 0.1% to 20.1%, per Sabesp's report, edging closer to the most severe operational limits. This decline happened despite December rains totaling 134 millimeters at Cantareira, below the historical average.
Since late September 2025, the system has operated below 30% capacity, hitting lows of 19% in early December – the lowest since the 2014-2016 water crisis. The December 30 rain of 17.6 mm was the month's third most significant but insufficient to offset the shortfall. In the capital, December saw 177 mm, 3.7% under average.
ANA and SP Águas announced on December 31 that January withdrawals will be capped at 23 m³/s, with water transposed from the Rio Paraíba do Sul. Cantareira has five operational bands: normal (≥60%, up to 33 m³/s), attention (40-60%, 31 m³/s + support), alert (30-40%, 27 m³/s + support), restriction (20-30%, 23 m³/s + support), and special (<20%, 15.5 m³/s + support).
The Integrated Metropolitan System, encompassing six other reservoirs, stands at 26% capacity, in Arsesp's third contingency band (29-23%). Rationing would only trigger in the seventh band, with negative volume from 3.3%. Projections hold this level through September 2026, with no cuts foreseen.
Governor Tarcísio de Freitas's (Republicanos) administration emphasizes preservation efforts amid subpar rains and a 60% consumption spike from intense heat. Measures include nighttime pressure reduction (7pm to 5am), saving 57 billion liters, though it leads to temporary shortages in some neighborhoods. Further steps include a water management plan and accelerated projects, such as pumping up to 2,500 liters per second from the Itapanhaú River to the Alto Tietê System, boosting its capacity by 17%.
CGE forecasts showers starting January 2, with the capital's historical January average at 256.4 mm.
