Key Points • Community based monitoring of water quality and aquatic ecosystems such as Waterwatch in Australia comprise an important portion of worldwide community monitoring efforts. • Waterwatch data have traditionally been criticised as being of inferior quality compared with professionally collected data yet there are few published comparisons of the data sets. • Excellent agreement between Waterwatch and professionally collected data sets from the Australian Capital Territory were observed for electrical conductivity and pH indicating that the quality of these data are indistinguishable from professionally collected data. • Good agreement was observed between the Waterwatch and professionally collected turbidity and dissolved oxygen data particularly given differences in methods used to collect the data. • The quality of the data collected by the community based volunteers provides an opportunity to incorporate Waterwatch programs into jurisdictional wide monitoring strategies with confidence and allows augmentation of existing monitoring effort to enhance water quality management outcomes. Abstract Community based monitoring of water quality and aquatic ecosystems, such as Waterwatch in Australia, forms an important portion of the community monitoring efforts worldwide, however, such data are rarely accessible or used in decision making. Waterwatch data have traditionally been criticised as being of inferior quality compared with professionally collected data and as such have seen limited use and incorporation into government data sets. Water quality data collected from 2003 onwards by Waterwatch volunteers in the Australian Capital Territory region were compared with equivalent data collected by government agencies, consulting firms and academic institutions (professionally collected data). The water quality variables compared were electrical conductivity, pH, turbidity and dissolved oxygen. Excellent agreement between Waterwatch and professionally collected data sets were observed for electrical conductivity and pH indicating that the quality of these data are indistinguishable from professionally collected data. Good agreement was observed between the Waterwatch and professionally collected turbidity and dissolved oxygen data particularly given differences in methods used to collect the data and differences in sampling times. The quality of the data collected by the community based volunteers provides an opportunity to incorporate Waterwatch programs into jurisdictional wide monitoring strategies with confidence and allows augmentation of existing monitoring effort to enhance water quality management outcomes.