The Ruhrverband is one of the special statutory water boards in North Rhine-Westphalia. The special statutory water boards fulfil legally assigned, state tasks within the framework of water management in the state of North Rhine-Westphalia, such as the purification of wastewater. The tasks of the Ruhrverband are set out in the Ruhrverband Act (RuhrVG). The law contains fundamental provisions on the contribution standards and the assessment procedure. Further provisions are contained in the Ruhrverband statutes. Details of the calculation of contributions are set out in the assessment guidelines.

The association's expenditure for its members is calculated in the assessment of wastewater dischargers (cities, municipalities, commercial enterprises) in valuation units (for wastewater treatment) or square metres (for rainwater treatment) in accordance with the rules of the assessment guidelines. The expense for the member group of water users is calculated according to the total water withdrawal (if it exceeds 30,000 m³) and the type of use.

The Ruhrverband is mainly financed by membership fees, whereby the amount of the fee is based on the quantity and use of the water withdrawn and the quantity and quality of the wastewater and rainwater discharged. As the Ruhrverband is responsible for the entire Ruhr river basin, it is able to save costs in terms of personnel deployment, planning, construction and operation thanks to synergy effects. Planning across municipal boundaries enables cost-effective joint solutions.