Καθόλου αφελής η ερώτηση. Ναι, στα ελληνικά, αν δεν έβλεπα το αγγλικό, αυτό θα έλεγα κι εγώ. 'Εχω την αίσθηση, ωστόσο, ότι το "βιώσιμο", στην περίπτωση αυτή, δεν αφορά μόνο το καθαρά οικονομικό κόστος, αλλά και τα externalities, κοινωνικό και περιβαλλοντικό κόστος. Τώρα τι να πω κι εγώ...
Παραθέτω τον ορισμό από την Ofwat, τη ρυθμιστική αρχή ύδρευσης και αποχέτευσης Αγγλίας και Ουαλίας, μηπως και βοηθήσει.
Εδώ
The sustainable economic level of leakage (SELL) is the level of leakage at which it would cost more to make further reductions in leakage than to produce the water from another source. The SELL calculation should include all costs and benefits associated with different levels of leakage, including environmental and social ones. Operating at SELL should mean that the total cost to the customer of supplying water is minimised and appointed water companies are operating efficiently.
και εδώ
We require the water companies to operate at the sustainable economic level of leakage, which identifies the level of leakage that gives consumers the best value for money. It compares the cost of reducing leakage to the costs of maintaining a balance between supply and demand in other ways, such as developing a new water resource, additional metering or promoting the efficient use of water.