Under anthropogenic global warming (AGW) scenarios, southern Alberta, Canada, is projected to see decreased streamflow, and northern Alberta increased streamflow in the next century [Figure 10.12, IPCC 4]. Because of global climate models’ (GCMs) moderate resolution, it is uncertain exactly where the transition between the two hydrological states will occur. Using the observed instrumental records, there has been much recent research on the detection and projection of climate change trends in Alberta and in western Canadian streamflow [i.e., Rood et al., 2005; Schindler and Donahue, 2006; Rood et al., 2008]. The conclusion of this research is that Alberta, particularly southern Alberta, is running out of water due to global warming. In this paper, we critically examine this interpretation of the instrumental records in the northern Rocky Mountains.