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February 3, 2015

Sao Paulo Water Supply Threatened by Low Water Levels

After the worst drought in 80 years in 2013/14, officials from the city of Sao Paulo had hoped for a recharge of the city's reservoirs during this summer's rainy season. Unfortunately, it has not worked out that way.

The water levels in the six reservoirs that supply water to the city of Sao Paulo were at critical low levels at the start of the summer rainy season and the less than normal rainfall this summer has only managed to stabilize the water levels, but they have not resulted in any significant recharge.

The largest of the reservoirs is the Cantareira water system that supplies 45% of Sao Paulo's water. The Cantareira system remained at 5.1% of capacity as of late last week, which was unchanged for five days. In the Cantareira region, the January rainfall totaled 147.8 mm (5.9 inches) compared to the long term average of 271 mm (10.8 inches). Last October, the Cantareira system fell to just 3.3% of capacity, the lowest on record.

Other reservoirs that supply water to the city are faring only slightly better. The water level in the Alto Tiete system is 10.7% of capacity, up one tenth of a percent for the week. The January rainfall at this reservoir was 101.7 mm (4.0 inches) compared to the average of 251.5 mm (10.0 inches).

At the Guarapiranga reservoir, the water level rose to 48.2% of capacity, which was up from 47.8%. Their January rainfall at 247.2 mm (9.8 inches) actually surpassed the average of 229.3 mm (9.1 inches). The water level at the Rio Grande reservoir increased from 74.1% to 74.4%. The Rio Claro reservoir water level declined from 26% to 25.6% and the Alto Cotia reservoir was stable at 28.5% of capacity.

Water shortages and low water pressures are already being experienced in the city of Sao Paulo and it could get much worse if significant rains do not fall during the next three months. With a dryer than normal forecast for the remaining months of the summer rainy season, there is a legitimate concern that southeastern Brazil could be facing water and electrical shortages in the coming months.