3 maps explain São Paulo, Brazil’s water crisis

3 maps explain São Paulo, Brazil’s water crisis

Aerial image of Sao Paulo
FlickrFernando Stankuns

The worst drought to grip São Paulo, Brazil and neighboring states in 80 years is wreaking havoc on the local population. As of late October, key reservoirs hold less than two weeks’ worth of drinking water. Schools and health centers are closing early, dishes sit unwashed in sinks and restaurants are steering customers away from restrooms. Significant crop production declines are of deep concern, and because 50 percent of Brazil’s electrical energy comes from hydropower, possible power cuts loom. The president of Brazil’s Water Regulatory Agency warned that if the drought continues, the state faces “a collapse like we’ve never seen before.”

Brazil has more freshwater than any country in the world — 12 percent (French) of the entire planet’s total volume. So how is São Paulo — the richest, largest city in South America — running out of water? Three maps help tell the complicated story.

1. It’s a distribution and management problem

Brazilian population density and water stress chart

Brazil’s water resources and population are very unevenly distributed. The Amazon River basin contains roughly 50 percent of the country’s water, but only 4 percent of its population. About 80 percent of Brazilians are concentrated in megacities along the east coast, such as São Paulo and Rio de Janeiro, which rely on their own local river basins. Many of these cities are water stressed, due to their rapid growth and development.

WRI’s Aqueduct project recently analyzed water stress in Brazilian cities with more than 1 million people. About 40 percent of the population in these largest cities faces medium to extremely high water stress. This means that, depending on the particular location, as much as 80 percent of the water naturally available to agricultural, domestic and industrial users is withdrawn annually, leaving businesses, farms and communities vulnerable to scarcity.

Based on this relationship of demand and supply in a typical year, São Paulo, in fact, faces low to medium water stress. But this is far from a typical year. On top of São Paulo’s epic drought right now, a series of interconnected water management failures across the metropolitan area have hindered its ability to adapt to those conditions, according to Brazilian researchers. São Paulo demonstrates how destabilizing a drought can be — even in less-stressed areas — without adequate management. Other, more stressed cities in the region therefore could be at even higher risk.

2. It’s a variability problem

Water supply variability in Brazil

Water supplies can vary significantly from season to season and from year to year in Brazil. Most of Brazil experiences pronounced wet and dry seasons, otherwise known as high seasonal variability. Northeastern Brazil also has experienced considerable fluctuations in total average water supply from year to year — called high inter-annual variability.

The ongoing drought in Southeastern Brazil offers a prime example of how damaging a major supply drop can be over the course of a year. It began last summer, between December and February, historically the wettest time of year. The region received only half its usual amount of rain, according to NASA’s Earth Observatory. In the eight months since, rainfall has hovered at 60 percent below normal levels. There is concern among Brazilian experts that inter-annual variability may be increasing in southern and southeastern Brazil due to heavy deforestation of the Amazon.

Where variability is high, it’s important to store freshwater underground and in reservoirs during wet periods to sustain companies, farms and people through dry periods. The city of São Paulo depends, among other reservoirs, on the Cantareira System. Its six reservoirs, linked by 48 km of tunnels and canals, provide water to half the people in its metropolitan area. Sabesp, São Paulo’s water utility, reported Oct. 23 that Cantareira system was reduced to 3 to 5 percent of its maximum capacity. The utility is pumping water from the reserves below the intake pipes of the reservoirs.

3. It’s a deforestation problem

Expert consensus is building around deforestation as a major driver of this year’s drought and other serious dry periods in Brazil. In 2009, Antonio Nobre, a scientist at Brazil’s Center for Earth Systems Science, warned that Amazonian deforestation could interfere with the forest’s function as a giant water pump; it lifts vast amounts of moisture up into the air, which then circulate west and south, falling as rain to irrigate Brazil’s central and southern regions. Without these “flying rivers,” Nobre said, the area accounting for 70 percent of South America’s GNP effectively could become desert.

In recent years, Brazil has been hailed for its efforts to reduce deforestation — the average rate of clearance decreased 70 percent between 2005 and 2014. However, deforestation in Brazil jumped during the last officially recorded period, between August 2012 and July 2013, marking the first increase since 2008. Satellite analysis from Imazon, a Brazilian NGO, also indicates a 190 percent surge in forest clearing in August and September when compared with last year. The tree-cover loss is equivalent to an area almost five times the size of New York City.

In January and February, when rain is usually abundant in central and southern Brazil, the flying rivers failed to flow south, according to data from Brazil’s National Institute for Space Research. The exact science of how forest clearing affects the performance of the Amazon’s “hydrological pump” is still emerging, and further analysis is needed to determine how the timing and location of forest loss affects precipitation elsewhere. The “Flying Rivers Project,” an effort by Nobre and other Brazilian scientists to quantify the dynamics of atmospheric water vapor and forests in Brazil, provides some of the most robust data on the subject, including real-time and historic maps of air flows and water vapor in the region.

A need for action

This drought’s effects on Brazil will be complex. And the effectiveness of the country’s water management will deeply affect its energy, agricultural and industrial sectors, as well as its growing population. São Paulo’s ongoing emergency offers an extreme example of how dangerous a supply change can be, even in an environment with low-to-medium water stress in normal years.

In response, experts from NGOs — including WRI — formed an “Alliance for Water,” which proposed hundreds of short- and long-term measures to adapt to the current crisis and prevent future emergencies. WRI is also working with IUCN, the Atlantic Rainforest Restoration Pact, government representatives and civil society leaders on building landscape restoration strategies to help re-establish environmental services where they are needed most, such as the Sao Paulo watersheds.

But as the drought’s impacts continue to ripple throughout the country, it’s clear that more work is needed. Decision-makers across the country must learn from the lessons of this drought and increase water-use efficiency, enhance water-storage capacity and halt deforestation in the Amazon.

This article originally appeared at World Resources Institute and is reprinted with permission.