Current drinking water quality assurance rules in New Zealand refer to Escherichia coli and total coliforms as the primary methods for the microbiological monitoring of water quality. Here, we demonstrate how monitoring and surveillance for water resource management can be improved by dual application of E. coli monitoring and metagenomics. Data set contains 16S rRNA amplicon sequencing of reticulated drinking water and source waters. An assessment of contamination events and source water categorization.