The Cantareira system starts the summer with 28% less water than the same period in 2013, the day before the water crisis that devastated Greater São Paulo starting in 2014 and drove the reservoir to dead volume.
It is also the worst start to the rainy season since 2015, when dams were still recovering from drought.
In practice, the difference between the beginning of summer 2013 and 2025 is approximately 80 billion liters, or the equivalent of 38 days of water collection in Cantareira according to the parameters currently adopted by Sabesp.
On Sunday, at the start of summer, Cantareira had 20.9% of the useful volume, or 205 billion liters. Also on December 21, but in 2013 the system had 29%, or about 285 billion liters.
Natural flow
The amount of water entering the system in December is much less than expected for this time of year. Until this Monday (22/12), Cantareira had received a natural flow of 21.13 cubic meters per second (m³/s).
For comparison, the historical average for the month is 50.3 m³/s. In other words, only 42% of what was planned. In December 2013, the natural flow was 23.14 m³/s.
Until Monday, Cantareira had received 100 mm of rain in the month. In period, in 2013, it was 44.2 mm. However, natural flow is a more effective “thermometer” than rainfall volume itself in measuring the recovery potential of the source, because it is the water that actually reaches the dam.
As the ground around the reservoir has been dry for a long time, it will first need a lot of rain to soak the path that brings the water to the spring.
Unlike what happened in 2013, Cantareira now also receives water from the Paraíba River basin, by transposition to the Jaguari station, which provides 8.81 m³/s to remedy the situation in the system.
Among the measures adopted to preserve water, Sabesp favored the reduction of pressure in the network from 7 p.m. to 5 a.m.
In October, the state government presented an emergency plan providing for up to 16 hours of pressure relief per day and the possibility of rotation.
Fields of action against the water crisis
- Band 0 (reservoirs between 43.8% and 100%) – normal situation
- Band 1 (below 43.8%) – preemptively programmed pressure modulation
- Band 2 (less than 37.8%) – pressure reduction for 8 hours at night
- Band 3 (less than 31.8%) – pressure reduction for 10 hours at night
- Band 4 (less than 25.8%) – pressure reduction for 12 hours at night
- Band 5 (less than 19.8%) – pressure reduction for 14 hours at night
- Band 6 (less than 9.8%) – pressure reduction for 16 hours at night and use of pumps to explore dead volume
- Band 7 (level 0%) – rotation with daily alternation between the regions which will be supplied
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