Water Loss Control Programme in Sao Paulo, Brazil
The metropolitan region of Sao Paulo, Brazil, has 17 million inhabitants settled on 800 km2. The landscape is hilly, varying from 730 to 850 meters above sea level. The Sao Paulo Water & Sewer Co., SABESP, supplies water and sanitation services through a distribution network of 26,000 km of mains with 3 million connections, and through bulk sales to six municipalities. The water system is fully metered, and consumers have individual storage tanks because supply is not constant due to drought conditions and daily water shutoff.
In the last year of the case study, average production was 62 m3/s. The figure for real and apparent losses was 15 percent and 18 percent, respectively, compared to a total (real and apparent together) loss of 50 percent in neighbouring municipalities. “Real loss” is the physical escape of water from the distribution system, and includes leakages and overflows prior to the point of end use; “apparent loss” is essentially a loss “on paper” and consists of customer use that is not recorded due either to metering errors or unauthorised consumption. It is important to control both losses in water distribution systems.
SABESP underwent a thorough reorganisation process between 1995 and 2000 with the aim of achieving ambitious financial and operational targets. In the fiscal year of 2000, a USD 250 million net profit was generated, which allowed USD 400 million investment for 2001 to improve and maintain the systems.
The water distribution network of Sao Paulo works on a gravity principle, and much of the system is made up of old piping (nearly 30 percent of pipes are more than 40 years old). The distribution network delivers at high velocity with the old pipes, as they are typically undersized relative to actual demand, meaning that significant head-loss occurs during peak hours. An advanced pressure strategy was therefore compulsory to cope with such scenarios.
Another characteristic related to the Sao Paulo water supply system is low overall distribution storage capacity (1,500,000 m3), but a positive impact is that customers have domestic roof tanks.
Conflicts arising from the baseline situation
When the measures were launched, there was no explicit scarcity or shortage within the case study region; consequently, there were no immediate conflicts between different water users or interest groups. A potential conflict emerged in that providing the necessary financial sources for the enlargement of the dam system and transfer capacities posed a threat to public finances. The investment costs were estimated to equal the total three-year revenues of the water service of the region. An adaptation process, including demand management, seemed to be a more attractive choice.
Description of the applied measure, its introduction and operation
Response time: The programme reduced response time to customer complaints about visible leakage, bringing the 1994 72-hour average repair time down to 24 hours in 1999 and 13 hours in 2000.
Re-zoning: As part of the pressure reduction programme, it has been essential to rebuild main pipes in some sectors and zones. The intense expansion of the city, plus the presence of large sections of old pipes, causes excess pressures at night. New pressure zones were implemented to lower the average pressure in the zones and minimise pressure at critical nodes. The target was to re-zone five new sectors per year in the whole metropolitan region. The expected volume to be recovered was 3.1 million m3 per year.
Replacement: Apparent losses were attributed in part to inaccurate residential meters. The target of the initiative was to renew 1 million residential meters over a three-year period (2000–2002), using the criterion of maximum possible volume to be recovered. The average monthly gain from 250,000 meters changed was 3 m3. In 2002, USD 8 million was invested in new equipment, and the total amount recovered was 33 million m3.
Physical and ecological impacts of the measure
The predicted physical impacts and financial characteristics for the second phase of the project, 2000–2004, are summarised in the table below (See table). Real loss control for the period 2000–2004 reached 623.7 million m3, with a total cost of USD 92 million, while apparent loss control contributed a saving of 227 million m3, worth an estimated USD 47.5 million.
Resilience of achievements, sustainability of results
Such a programme, if rationally executed, is sustainable because the potential revenue from the programme covers the costs.
Some customers complained about having lower pressure than previously. The need for lower pressure than previously needs to be effectively communicated to consumers.
- Reduced the average pressure of the water distribution network: nearly 30 percent of the distribution system has pressure above 60 metres per head, while acceptable pressure in water distribution ranges from 25 metres per head to 42 metres per head.
- Reduced response time to customer complaints about visible leakage.
- Introduced an intensive, non-visible leak-detection programme in the entire network.
- Implemented re-zoning in 15 sectors.
- Renewed and upgraded 1 million household meters in the system.
- Replaced 26,000 large consumer meters.
- Reinforced antifraud actions.
- Enhanced the bulk metering system.
- Dedicated management staff.
- Well-planned programme for loss control.
- Availability of funds.
- The company adopted a more active position in daily operational routines.
- Evaluated savings for the 417 installed PRVs (pressure reducing valves) when valves are installed is 1.5 m3/s.
- 30,000 leaks fixed per month: around 10 percent (roughly 3,000) occur on main pipes, and 90 percent on service connections.
- Expected return on investment (USD 139 million) from 2000 to 2004 is USD 272 million.
This case study on water loss in distribution systems can be applied widely across the MENA region. Dedicated and professional management is just as important as the availability of medium-term loans to finance the investments.
- USD 139 million for the period 2000–2004
Marcelo Salles Holanda, SABESP
- Thornton, Julian. Water Loss Control Manual, McGraw-Hill (2002)