Instream Flows for Recreation: A Handbook on Concepts and Research Methods

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PREFACE Our job was supposed to be simple: Run the river, measure the flows, and estimate how much flow would be needed to maintain the river's recreation experiences. But which flows, and which experiences? We were four days into a seven day trip on Alaska's Gulkana River, and already we had encountered -- endured in some cases — a full range of both. Starting out in two overladen rafts and a snap - together vinyl canoe on a bright afternoon, we had learned it was possible to float down the narrow but relatively deep headwaters on a measured 26 cfs, while R even three times that flow didn't allow us — or the spawning king salmon — passage ` through the riffles that appeared downstream as the channel widened. Making little progress pulling our rafts over the bars, we cheered the light rain that A..w► began to fall on our second day, a rain that turned into a full scale downpour by that afternoon. Unfortunately, the added flow "Boat dragging" on Alas 's Middle Fork of the Gulkana did little to help our situation: the river had River at low flows. picked up gradient and now presented a boulder- choked channel. The river was running close to 300 cfs and had plenty of depth -- just enough to fill your hip waders — but only the canoe was managing to find a clear route through. By the time we hit the upper river's only rapid, a short zig -zag gorge, the river was roaring but still couldn't provide a navigable run. We ended up lining the rapid. The rain didn't stop that day, nor for two more, and the river reached its bankfull stage sometime after we had slogged through 35 miles of meandering flat water but before we got to the usually manageable Canyon Rapids, a quarter -mile Class III -IV run. We had almost been flooded out of one camp, and watched in dismay as cutbank after cutbank sloughed off into the river, turning the once clear green water into a muddy soup that killed the fabled salmon and grayling fishing — at least for us. In the long run, of course, the erosion and the soon - to -come deposition were simply part of the dynamic system that nurtures good fish runs, not to mention creating expansive camping beaches for which the river is also known. But as we scouted the suddenly challenging whitewater of the Canyon, looking for a safe route around a huge hole at the end of the run -- and not even thinking about trying to measure the raging flows — we began to fully understand the potential complexity of the instream flow issue. Conceptually simple, determining flow needs for recreation can often be practically challenging. The complexity begins with measuring flows, but extends very quickly to the relationship between different flows and the conditions that create a high quality trip. As an early study of its kind, we could have predicted the Gulkana would have much to teach us. But in the five years and dozen or so studies we have collectively worked on since, there is still much to learn. Canyon Rapids at higher flows.