Potable water: a leak in the pipes...

The quality of the water mains supplying the population with potable water is a significant global issue. In many developed countries, mains dating back to the 1960s or 1970s are now obsolete and raise a number of problems.

In France, about 1,300 billion litres of water are lost each year (about 23 percent of the water that passes through the mains system), without the water utilities making any major investments to reduce these leaks.

In the United States, the average rate of pipe leakage is around 16 percent, but can be as high as 45 percent depending on the state or region.

These water losses are real ecological disasters, but with a replacement rate for defective pipes of no more than 1 percent per year, the issue is obviously not getting the attention it deserves from public decision-makers.

A cost minimization approach

In their article, Elissa Cousin and Emmanuelle Taugourdeau propose a static cost minimization model for water utilities.

The aim of this model is to determine a cost-efficient water mains quality index. The model incorporates a number of parameters such as pumping cost, water treatment cost and leakage rate. It makes it possible to analyze the impact of mains quality on the cost of water and on demand.

The model is simulated for American and French utilities, bringing geographical differences to light.

Mains quality called into question

The principal results show that the mains quality (age and materials used) observed today is often below the optimal index determined using the theoretical model and calibrated on French and American data, even through the calibration tends to produce a low estimate of this index. In addition, the authors show that the increase in mains quality is particularly sensitive to the cost of pumping and water treatment.  

In the event that the cost of improved quality is passed on to the consumer, however, the increase in the mains quality entails a relatively moderate price increase.

Finally, the case of the American water utilities highlights strong geographical differences, which may explain why some regions have lagged behind in renovating the mains.

Global Water Forum

The article "An analysis of water main quality indices of French and American water utilities", published on the Global Water Forum on 28 November 2016, is taken from an academic article, "Trade-off between water loss and water infrastructure quality: A cost minimization approach", by Elissa Cousin and Prof. Emmanuelle Taugourdeau, Water Resources and Economics, pp. 28-42, 20.