Stated most simply, the water flow differences between a heavily logged watershed and a fully forested watershed are analogous to the drainage differences between a paved parking lot and a lawn. The rainfall may be the same, but the runoff, carrying anything loose from the parking lot is immediate and swift. Then there is nothing. The drainage from the lawn is slow, continuous, and clear. The runoff characteristics of a heavily logged watershed are high water, flood-like events with murky (undrinkable) water that often cannot all be captured (above a dam) and must be released when it is least needed. Then, between rains or into summer, rapid and severe dropping of the water level and warming of the water. In a fully forested watershed heavy rain events are blunted by the canopy and complex root/soil systems, water release is slow, continuous, clean, and cold. It would be most interesting to look at the historical flow data on the Green river. Always curious, I took advantage of an opportunity to fly in a private plane over the Upper Green watershed in mid-August 2003. Flying out of Renton, one necessarily ascends the lower Cedar River watershed first. The first thing that struck me was that the Cedar River in August, BELOW the water withdrawals for Seattle, was MUCH BIGGER.than the lower Green River. That was strange because, in my mind, the Cedar River I had always remembered as a minor river and the Green a major river, but here the minimal summer flows were quite dramatically reversed. If a picture is worth a thousand words, then here are about 20,000 words worth of what we found in the TWD “managed” watershed. To my non-professional eye it appeared that the watershed had been as intensively logged as any privately owned forest I have ever seen. To my eye, 90% or more was in early reforestation. There appeared to be very little marketable timber left to cut. In some places it appeared that logging had occurred right down to stream level banks without the typical riparian set backs for protection of the river and it’s biota. For comparison we flew over the Upper Cedar River watershed managed by the Seattle Water Department. The pictures are a shown. Basically, in comparison, the Cedar River watershed appears to be a pristine, old growth preserve. There are some very interesting questions that spring from these observations, The first question is: What is the effect of the logging activities in the Upper Green watershed on the runoff and water quality characteristics and are those effects consistent with the charter of the TWD to “manage” the watershed primarily for water production, quantity and quality. How do the streamflow effects of the logging impact the river BELOW the TWD watershed area after the withdrawals for Tacoma water. Is
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