HYDROGRAPH SEPARATIONS IN AN ARCTIC WATERSHED USING MIXING MODEL AND GRAPHICAL TECHNIQUES

Storm hydrographs in the Upper Kuparuk River basin (142 km(2)) in nort hern Alaska were separated into source components using a mixing model and by recession analysis. In non-Arctic regions, storm flow is commo nly dominated by old water, that is, water that existed in the basin b efore the storm. We suspected that this may not be true in Arctic regi ons where permafrost diminishes subsurface storage capacity. Streamflo w during the snowmelt period was nearly all new water. However, all su mmer storms were dominated by old water. Storms in a neighboring basin were dominated by new water but much less than was the snowmelt event . Thus a large increase in old water contributions occurred following the snowmelt period. This increase continued moderately through the su mmer in 1994 but not in 1995. We credit the seasonal changes in old wa ter contributions to increased subsurface storage capacity due to thaw ing of the active layer.