Much of the surface runoff in the interior Pacific Northwest is related to frozen soil conditions. The processes involved are generally less well understood than those for corresponding unfrozen conditions. We have undertaken intensive monitoring and modeling of field conditions. This work has lead to a better understanding of the processes involved. The question remains, however, how to extrapolate those processes to larger scales that are involved during flooding events. The difficulty is that many of the required parameters are spatially variable. We used observations of a runoff event which was strongly affected by the presence of frozen soil to establish what landscape features are effective sources of spatial variability. Measurements represented runoff from areas ranging from 1 m2 to 250 km2. At the smallest scale, runoff was extremely variable and controlled largely by vegetative effects on snow distribution. These effects could be effectively parameterized at a scale of 30 m2. At the small watershed scale, topography was the dominating source of variability because it controlled the amount of incoming solar radiation to the snowpack and/or frozen soil and the redistribution of snow by wind. These effects may be parameterized within elevation zones. Meteorology, as influenced primarily by elevation, was the predominant source of variability at the larger watershed scale.
Mark S. Seyfried USDA Agricultural Research Service 800 Park Blvd., Suite 105 Boise, ID 83712 Phone: 208-336-5696 Fax: 208-336-1502 E-mail: mseyfrie@nwrc.ars.pn.usbr.govGerald N. Flerchinger USDA Agricultural Research Service 800 Park Blvd., Suite 105 Boise, ID 83712 Phone: 208-334-1363 Fax: 208-334-1502 E-mail: gflerchi@nwrc.ars.pn.usbr.gov