The Assembly of Associates consists of up to 152 delegates, 150 of which are being delegated by the association's members or elected by voting groups. The number of delegates per member or group of members is determined by the amount of financial contributions, which in turn is calculated on the basis of the amount of water abstracted from or the polluting load discharged into the river. Two delegates are appointed by the chambers of agriculture. 

Tasks of the Assembly of Associates:

• Establishment of the association's statutes
• Establishment of assessment guidelines
• Election of the Supervisory Board
• Approval of the annual financial statement
• Approval of the economic plan
• Approval of the plans on construction activities and other actions

Since the revision of the Ruhrverband act on February 7, 1990, delegates from the groups of members are appointed to the Assembly of Associates for five years.