High water observations

On Sunday, following the edicts of a decades-long tradition, I slid my whitewater kayak into the flow of Sonoma Creek near Glen Ellen and headed down stream to see what a weekend of rain had created. The creek was the size of a small river, moving like a freight train at a volume I would guess exceeded 3,000 cubic feet per second. This is not, by the way, an activity the uninitiated should even consider, especially during high water. I’ve been running rivers for years, I know Sonoma Creek’s charms and its hazards fairly intimately, but with all that, the power of Sunday’s flow caught me somewhat by surprise and dictated course corrections I hadn’t planned on having to make. And it revealed a potentially deadly hazard I only avoided because I had carefully scouted a safe take-out site in advance.

What I saw on that trip was instructive about the overall health of our principal watershed and the impact we who live in it have had over the years.

The two most obvious discoveries involved the color and volume of the water, which was milk-chocolate brown. That’s not unusual for high-water events, but more and more common with the inexorable increase in soil erosion caused, at least in part, by the expansion of vineyards and their encroachment into the riparian corridor of the creek. Cultivated farmland, once it’s saturated, inevitably surrenders soil to water runoff, and vineyards – like fields of corn and hay – significantly reduce the capacity of the land to hold back and absorb rainfall. Simultaneously, because Sonoma Valley agriculture commonly requires irrigation, growers pull water out of both the creek itself and from the underlying aquifer to which the creek is connected.

The result of all this is increased extremes of high and low water, with flow further reduced during dry times because watershed retention is lower, and dramatically increased during heavy rains because the denuded landscape can’t hold water back.

It’s not clear what the actual figure was, but a good guess suggests that Sonoma Creek was flowing at something well under 5 cubic feet per second before the Pineapple Express roared through, which means it could have increased in volume by something approaching 1,000 percent.

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