Hydrologic Model

Testing the Model

A comparison of modeled and actual streamflow. If the model accurately calculates snow accumulation, snow melt, and streamflow; and can accurately calculate the differing snow accumulation and melt in the forest and clearcut, we have some confidence that it can accurately model the effects of logging on streamflow. A comparison of modeled and actual streamflow is shown in the figure below. The modeled and observed flow are very similar.

Summary of Results

1. Cutting within the lowest elevation (H80-H100) in the watershed has no effect on peak flow.

2. Cutting within the zone (H60-H80) has a modest effect on peak flow at low intensity (1/3 of the zone) but a considerable effect at higher intensity (2/3 of zone). The results are variable from year to year. The peaks were increased considerably more in 1997 than in the other years.

3. Harvesting the zone (H40-H60) has a greater effect per unit area than the (H60-H80) zone. The effect is consistent from year to year.

4. The peak flow effects were considerably greater in 1997 than in the other four years. This may be because there was an unusually high low elevation snowpack that year.

5. Harvesting in the highest zones (alpine) had a similar effect to the lower zone.

6. Weighting harvesting above H60 is a reasonable concept for snow dominated watersheds such as Redfish Creek.