Comments on Study of Forest Cover and Water Resource

Hi Earle

I agree with you 100%.

All I was doing was pointing out that the focus of the TPL study (done in partnership with AWWA) concerned water supply for humans.

The points you make also lead to the conclusion that one cannot restore the Russian River simply by lowering flows, without restoring flow in the tribs and maintaining the base flow that keeps those tribs clear and cold.



RE: Comments on TPL Study

Stephen has it partly right, in that a significant part of the developed water that the Sonoma County Water Agency relies on for diversion at the Wohler intake is Russian River water stolen fair and square from the Eel system a century ago and percolated through the alluvium to polish out most of the goop. But the Sonoma County portion of the watershed has always sustained salmonids in the forested tributaries, and indeed, some grass-covered watersheds. This base flow, that stays cold and well-oxygenated through the heat of late summer is water that has percolated into the soils in the upper watersheds in winter, and emerges when the fish really need it. Without that dead-of-summer surface-emergent groundwater, the Russian would have no anadromous fish. The mainstem was of value to them for ingress and egress, and they were reared to a size that offered them higher ocean survival in an estuary at Jenner that was barred from the ocean by the gravel beach.

Preserving forest cover, and restoring a perennial grass cover on the grassier watersheds, is the way to assure survival for that component of aquatic life that relies on high quality, cold, oxygenated baseflow. We’ve degraded the watersheds by careless logging, careless grazing, and careless road design, construction and maintenance. But the watersheds can be preserved as open space. They can be managed thoughtfully and still produce marketable and sustainable resources, whether in private hands or public, while recovering their aquatic life. But we can’t let people think that the only water we need is something we get from somewhere else.

And I know I’m preaching to the choir. 



Regarding ‘Protecting the Source: Land Conservation as a Drinking Water Protection Tool’ at (Caryn et al 2002)

“A TPL study in 2002 found that treatment costs for surface water systems varied widely depending on the amount of forest cover in the watershed. The study indicated that costs could decrease by as much as 20% for every 10% increase in forest cover, up to what appears to be an optimum level of forestation at about 60%”.

This is very interesting, but not totally relevant to our situation. Most water sources in Sonoma County are from groundwater or from surface water that has percolated down through gravel beds under the Russian River.