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The status of surface water and groundwater
The brief Eaufrance - n°12 -

Making the benefits of groundwater preservation more visible

It is often difficult to justify work to preserve groundwater given the “invisibility” of the expected benefits. An economic assessment of benefits using the avoided-costs method can assist water managers in explaining and clarifying those benefits.


Groundwater provides a number of functions and services (natural production of high-quality water, natural distribution of water over wide areas, supply to the linked surface ecosystems, an “insurance policy” against droughts and pollution is some cases, etc.) that are now threatened by overuse and pollution. That being said, local stakeholders and public decision-makers have difficulty in justifying work to preserve groundwater. This is because in comparison with the upfront costs of the work, the objectives targeting good status set by the Water framework directive (WFD) and presentations of the expected benefits, often uncertain and lying far in the future, are less convincing. In this context, it may be useful to call on economic assessments, such as the avoided-costs method for drinking water. This method can be used to express in economic terms some of the benefits that may be expected from protection projects and thus facilitate their comparison with the costs of the work.

Two main types of costs

The avoided-costs method evaluates the costs that the direct users of groundwater (water companies, consumers of drinking water) would bear due to degradation in the water quality. Other methods exist to determine the potential benefits for society, however the avoided-costs method is the simplest to use because it simply adds up the costs that would be avoided if the resource is preserved. Two different types of costs can be revealed. The first concerns the strategy selected by the company supplying the drinking water in order to continue supplying high-quality water, e.g. drilling a new abstraction, implementing a secondary source, installing a new treatment plant, etc. In 2011, the Seine-Normandie water agency calculated that the treatment of nitrates alone to make water drinkable cost 0.31 euros per cubic metre of water in the basin. If that cost were applied to the average daily consumption of a city such as Paris, the cost per day would amount to approximately 160 000 euros*. On the national level, depending on the local context and the strategies implemented, costs can vary from 0.02 to 1.02 euros per cubic metre of drinking water produced, which corresponds to a maximum of 525 000 euros per day for a city such as Paris. The second type of costs are those linked to avoidance behaviour of consumers if they have lost confidence in the quality of the water supplied to their homes. In 2013, the outlays incurred by this behaviour were estimated at between 151 and 366 euros per household per year for the purchase of bottled water (4% to 30% of households) and between 61 and 257 euros per household per year for the purchase of treatment systems (filters, etc.)

Example of the Alsatian aquifer

Between 2002 and 2006, BRGM conducted a study to determine the past costs incurred by the non-preservation of Alsatian groundwater over a 15-year period. Almost one-third of the local governments producing drinking water from the aquifer were confronted with nitrate and/or pesticide pollution in abstractions over the period. The pollution resulted in a additional cost of 26.5 million euros for the production of drinking water, leading to an increase of 30 euros per year in bills for a household of four, plus another 14.3 million euros spent for avoidance behaviour. Many people are relatively unaware of this information and the costs that represent a non-negligible transfer of expenses, given that the water sector and, in the end, the consumers must pay for problems for which they are not responsible.

* On the basis of 515 000 cubic metres per day

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