The WaterNSW macroinvertebrate monitoring program (MMP) was established in 2002 to support catchment health assessment for the Greater Sydney Drinking Water Catchments (SDWC). The program consists of an annual AUSRIVAS survey of 86 stream sites located throughout the SDWC. Since its inception, the program has evolved significantly to incorporate adaptive learning and improve integration of the program outputs into catchment management. The most recent program review applied a range of statistical techniques to the long-term dataset to identify spatiotemporal trends, explore environmental drivers of community composition and assess the statistical power of the monitoring design. The review identified spatiotemporal trends at the individual site scale and showed that even annually collected macroinvertebrate data are sensitive to broader land use gradients. The power analysis revealed that site replication was often insufficient to detect statistically significant temporal trends at the spatial scales that were commonly used to interpret the monitoring data. The review also yielded several additional learnings with respect to program design principles and uptake of monitoring data into decision making and management. The revised study design supports stronger hypothesis-driven monitoring objectives while still maintaining the continuity of long-term monitoring dataset and fulfilling regulatory requirements.