La redevance eaux pluviales liée à la rétention de Poznań — Le dispositif de remise à coût évité d'Aquanet (Pologne)

Coût indicatif

Faible (< 50 k€) — Municipal small-retention grant budget: 1,000,000 PLN/year, covering up to 80% of device costs (capped at 50,000 PLN for housing cooperatives, 6,000 PLN for individual households).

Délai jusqu’aux résultats

Long (> 3 ans) — Discount tariff operating since around 2021; current rates effective August 2025.

Personnel et compétences

Aquanet S.A. (water utility, administers the tariff), City of Poznań (co-runs the small-retention grant programme)

Conditions de réussite

• Property owners installing qualifying on-site retention devices (rain gardens, retention tanks) to reach the >20% retention threshold
• Sustained municipal grant budget to offset installation costs and encourage uptake
• Public acceptance of stormwater charges — a peer-reviewed comparison notes Warsaw and Kraków have not adopted equivalent fees, citing public resistance

Modes d’échec courants

• No published data exists on total impervious area affected or aggregate retention volume achieved city-wide, so measured effectiveness is unverified
• Public resistance to new stormwater charges has stopped larger Polish cities (Warsaw, Kraków) from adopting equivalent schemes