making sense of flow charts

Anyone know of a resource online that explains these? For example I was looking at the Missouri river data, and it’s hard to understand what the numbers mean. On top of that, I couldn’t find a way to compare them to anything older than last year.

I was looking at garrison dam. Now it’s at 1815. Last year it was about the same. But I don’t know if that’s high or low?!? It tells the flow rate in cubic feet per second, but what does that mean.

I guess I want to know how to interpret these things and find something to compare to.

You really need to be familiar …
… with the location in question. Once you know what “normal” is, you can make judgements accordingly.

As far as comparing current data to previous, I’ve found the USGS site to be very awkward and “unfriendly” to anyone who doesn’t have its workings figured out. I’ve nearly given up trying to look up old data, because there’s no clear path to follow, especially after you’vr entered your request in a non-proper format. I succeeded once at finding some old flow data, but for the life of me I can’t recall what I did to keep from getting an error message.

There is a contact on the USGS gauge sites where you can ask any question. They are pretty responsive.

Also, all terms are defined.

Each gauge site will contain notes that most folks miss. Like a notice that despite the weather the river may be up or down depending on how much water the two upstream resevoirs draw off or discharge.

I look at the gauge height and look at the river, preferably after a run. I then can figure out what the water is like at 2.6 or 4.0 and which boat to use.

2.9 and up, I can go anywhere on my river without hitting bottom. At 2.7 I have to ‘river dance’. At 2.5 I’ll be getting out and dragging. So you can see what impact small readings have on a particular gauge/river section.

Sometimes the gauge is located a distance from the section of river you will be paddling. The only way for the gauge to be useful is to observe the water and then look at the gauge.

Look at the historic average to see what the river level is most of the time. That will probably be decent paddling.

Look at the flood stge for that gauge. I rarely ever reference the discharge rate associated with the stream height. It is interesting to see the relationship and useful to compare to strange streams you might visit when only a discharge rate is given.

Aaaggg! De words 'Flow chart"
still sends shivers up old programmers spines…


if it’s whitewater

– Last Updated: Jun-17-08 3:10 PM EST –

you might be able to find some info on AW's site. Sometimes there's a report giving the class of run and what the paddler experienced at a given level, along with their recommendations of levels that stretch is runnable at. Sometimes they'll be some pix and maybe a video of a particulat section. As already mentioned, nothing beats experience with a particular stretch, and knowing what the flow was that day you paddled. Got my local stretch down so good, from 400-3500 cfs, I know what eddies and waves to seek out at any level. Something about doing that stretch 150 times...;-)

= American Whitewater

links to the USGS gauges, plus information about a lot of stretches of river.

There are some basic stats on the USGS pages if you check “graph w/ stats” – min, max, median, 20th and 80th percentile – but there’s no way of knowing what that means for paddling unless you’ve seen the river at a few different levels.

Those figures on the flow table CAN be pretty useful, even if you’re not familiar with the river. The median flow figure is the most important. It is the flow in cubic feet per second that, half the time on that day of the year the river was flowing more water, half the time it was flowing less water. So it’s a very good indication of “normal” flow for that date. Now…if you know that the river is ORDINARILY floatable with no problems at normal levels, and the river’s flow is pretty close to the median, it should be floatable. That same figure is represented on the flow graph by little triangles. If the flow on the graph is pretty close to those little triangles, it’s pretty close to normal. The 80% and 20% exceedence figures are a little less useful. The higher number is the flow at which, only 20% of the time it was flowing higher than that on that date. On some rivers, it can be a good indication of the high end of paddle-able water, but you have to know the river to know if that’s true.