Glacier-fed River Runoff?
I was wondering what to expect of stream/river flow rates now (last of May) compared to to mid August? The river we will be floating feeds directly out of a glacier up high, has a wide braided section, followed by a narrow canyon stretch. This is all in a 25 mile length of river in the Alaska Range south of Fairbanks.
I have a feeling weather conditions (heat and/or rain) in August may influence flow rates but would you expect there to be much drop from current flow from what it looks like now?
As always, it depends on the weather, the river, and even what section of the river.
Rivers like the Matanuska are effected some by rain lower down, but unless it's torrential rain, there isn't much effect up at the top. Long stretches of heat are the usually required to bring it up, and they seem to have a cumulative effect, as the water is generally low until mid July. By then the heat of the day and cool of the night, causes large swings in river flow.
Glacial rivers that have a longer reach and drain a larger area are more effected by rain, but that's because they are less glacial and more rain/ground water filled.
I don't expect glacial rivers to fluctuate much in May/June. Just a gradual rise over multiple weeks. But severe weather of any type can bring faster change.
Another significant force in glacial river flow is ice dammed lakes; in, behind, or on top of glaciers. There are lots of them around, and when they let loose the water can rise very quickly for a day or so.
Last year (2008) in Aug, on your river, the heat was moderate and the rain was light and sparce...and that river could be crossed at 100+ places.
Two years ago (2007) during early August, the sunny days were really hot by Alaskas standards and then the rain that came was of biblical proportions....and at times that river was 1/2 mile wide, raging, could not be safely crossed on foot anywhere- and I drifted many, many yards downstream in 37 degree water and nearly did not get out, just to prove it to myself. Crossing had to be done on the glacier, at the foot of the glacier. And that glacier at the headwater of that river is always very easily crossed, unlike many other glaciers.
On normal days with manageable water, plan your river crossing in the AM. Them glacial rivers can get a foot (or more) deeper in the PM. Keep in mind that where you will be, the water is one minute off the ice. Six miles downstream, the water is one hour off the ice on those warm days. And the glacial water will be 36 or 37 degrees. Your feet will hurt at first, then go numb. On the other side, after walking stiff legged like Franenstein, more foot pain followed by "normal" foot and leg feeling will resume. (Why do we do this stuff? <rams>)
This coming August, 2009, ?????????????????????????????????????????????????? ??
Thanks guys! My BIL just did a weekend trip to view the canyon and flat braided area above the canyon. We were kind of curious if water rate/flow now may be similar or +/- what we could expect in August. It sounds like it will be pretty tough to predict and likely could change from day to day depending upon the weather. I have always liked predictability when planning a trip...especially when 25 miles from the nearest road but I don't think it will be possible!
The 2 things that concern us are: 1) having difficulty getting a larger (100 lb) framed raft down the shallow, wide braided area just below the glacier and 2) the narrow canyon stretch raging about 15 miles down river. It sounds like we may be able to portage or long line the worse spots in the canyon....if it isn't too terribly bad.
The worse case scenerios would be that there is too little water in the upper stretch and we would have to hike 25 miles out....and have a plane pickup our gear at our dropoff spot at the glacier. Too much H20 in the lower canyon and have to stash the raft and hike 9 miles around the canyon to the main road....and possibly pick up raft later after a lengthy portage! I'm not sure what the odds will be that we will have smooth sailing all the way? I guess things can never be that simple...but that is what makes life interesting!
The only thing relatively sure is that there will be a lot more water in August than there is now.
You will be fine
The river above the "narrow" stretch will hold enough water in a channel for you to float. I have driven across the bridge that the river crosses MILLIONS of times. The only part I would worry about being too shallow is after the narrow spot, but figure you will still make that, but it does braid a whole bunch in there. You will have no problem on the from the glacier to the narrow part and feel you will be able to float the rest high water or not. Just pick the right channel.