This paper focuses on the parameterized-ordered weighted averaging (OWA) method. OWA is a family of multicriteria evaluation (or combination) rules. The proposed approach uses a parameter that serves as a mechanism for guiding multicriteria evaluation procedures. The parameter is incorporated into a method for obtaining the optimal order weights and for developing a transformation function. The function provides us with a consistent way of modifying the criterion values so that the multicriteria combination procedures can be guided by specifying a single parameter. The parameterized-OWA method has been implemented in a GIS environment as a GIS–OWA module and it has been tested in a real-world situation for developing management strategies in the Cedar Creek watershed in Ontario, Canada. Given a set of evaluation criteria, the problem is to evaluate areas in the watershed for rehabilitation and enhancement projects. Using the GIS–OWA method, a number of alternative strategies for rehabilitation and enhancement projects have been generated and evaluated.