The Ontario Branch of CWRA began operating informally in the early 1970s, conducting conferences and workshops. In 1975, at the request of the National Board of Directors, the branch took on the responsibility of initiating an improved national membership management process. At about the same time, publication of the Canadian Water Resources Journal began as an Ontario responsibility, with initial financial support from Environment Canada. In 1991 the Ontario Branch was incorporated.
The aims of the Ontario Branch mirror those of the Canadian Water Resources Association as a whole, while the Branch may focus on regional or local issues. Membership in CWRA is a national membership. However, members in good standing are automatically members of the provincial branch. The Ontario Branch membership consists of about 300 individuals, partnerships, and other legal entities.
Operations of the Branch are managed by a board composed of not less than ten directors, who are elected at the annual meeting by the members. All provincial directors are CWRA members. Each director is elected to hold office for a period of one year. The directors are responsible for the election/appointment of officers and committees.