Estimates of Canadian Pacific Coast runoff from observed streamflow data

The monthly flows to the North Pacific Ocean from North American watersheds located between 47 and 60°N latitude were estimated for the period 1950–2007 using observed and reconstructed streamflow data from 74 hydrometric stations. These new estimates were compared to estimates made from the three stations used internationally to estimate flow to ocean stations in this region. Complications with simple reconstructions and estimates for ungauged areas are discussed with respect to hydrologic process and limits to the use of the data. These monthly estimates attempt to better reflect the seasonal patterns of streamflow from a complex hydrological area where streamflow is generated through a mixture of pluvial, nival, and glacial processes. These new estimates suggest much larger volumes of freshwater flow into the North Pacific than those based upon only the three ‘flow to ocean’ stations. The methodologies used demonstrate what idiosyncrasies must be considered to improve means to extrapolate monthly discharges in this hydrologically complex region.