other structures include fixed charges per hectare for nonmetered agricultural abstraction or a price per megawatthour for energy production in belgium flanders region the level of the tax varies with the quantity of water abstracted for groundwater abstraction water abstracted is sometimes paid through increasing block tariff ibt the volumetric price is higher for larger volumes in contrast the volumetric price sometimes decreases for larger volumes in the case of surface water the socalled decreasing block tariff dbt one issue with decreasing or increasing block tariffs is that the market signal sent to consumers on the value of the resource might become misleading