Given the high degree of variation in water governance practices across Canada, and the rapid rate of water-related legislative change in some provinces over the past decade, the purpose of this paper is to provide a systematic review of water legislation and governance that examines all thirteen provinces and territories, focusing on formal legislation and policies governing drinking water, watershed management (including source water protection), water rights, and water exports. We analyze legislative variation using concepts of harmonization and subsidiarity as a means of assessing the rationale for differing degrees of and approaches to federal and provincial involvement in water policy. Our review suggests that while variation may be appropriate, fragmentation is not. On this basis, we argue that some water issues would benefit from greater harmonization (which in many instances will imply greater federal involvement). In the cases of drinking water, source water protection, and water exports, increased harmonization at the federal level may be warranted. In contrast, whereas improving the federal role remains critical in terms of transboundary water management and water rights, this relates to its traditional activities of coordination, research, dissemination and funding rather than regulatory harmonization per se.