In recent years, citizen groups have attracted attention as public service providers as they collaborate with river administrators for river management. However, as time has passed since their establishment, some citizen groups are facing various difficulties in continuing their activities. For this study, we administered a questionnaire survey about the active mass, which evaluates their activities quantitatively, and factors for activity continuation, which were extracted from earlier studies of citizen groups related to rivers. Stepwise multiple regression analysis and correlation analysis were applied to the responses of 64 citizen groups to estimate the factors affecting the active mass variation.Partial correlation network analysis was conducted to estimate the relations among the factors, based on the assumption that a certain relation exists between activity continuation and the variation of the active mass of citizen groups. The factors were discussed using results of these analyses.