Here's something to think about - and I hope someone has some good
answers or can point me to a good source of info...

We have been doing some canoeing trips as a part of a summer orientation
program here at the University of Virginia. This year we have had to be
very conscious of river levels due to an unusually wet spring and early
summer around here. (Oddly enough, we had a record drought last year -
oh well.) I have found myself spending a lot of time explaining river
gauges and river levels to a variety of people in our organization so
they have some idea about risk management.

So now I have come up with a pretty standard speech explaining classes
of whitewater, river levels and water volume. Classes of whitewater
somewhat equates to classes of rock climbs - that seems to go over well
with most folks. However, people have a difficult time with
understanding river levels (what does 5 feet on this gauge mean?). They
also seem to understand the concept of CFS but it takes a little time
for them to grasp that just because CFS doubles, level does not
necessarily double and that 3000 CFS on the Maury River in Virginia is a
good bit different than, say, 3000 CFS on the Colorado

First question - does anyone have a good explanation for what river
level is supposed to represent and a good way to explain some of the
things above without degenerating into a technical hydrodynamic discussion?

Second (and partially related question) - I'm probably missing
something obvious here but I can't see the forest for the trees. I'll
use a specific example and we can generalize from there.

Looking at the James River (VA) gauge at Buchanan, you see that the
river is at a particular level and CFS - let's say, for example, 4.75
feet and around 3800 CFS, give or take. Looking downstream, we see that
the Maury River flows into the James at Glasgow, adding its flow to the
James at that point. We see that the Maury River at Buena Vista (a ways
upstream from the confluence) is running at 4.5 and around 2800 CFS.
Now moving downstream on the James, we look at the James River at
Holcomb Rock and the gauge reads about 7.25 feet and about 6000 CFS and
change. Common sense would say (river features like dams excepted) that
part of the extra CFS would be from the water coming from the Maury.
However, the ratio of level / CFS from Buchanan to Holcomb Rock seems
to be pretty continuous, regardless of the level / CFS being added by
the Maury.

So what gives? Is this a situation that is particular to this area or
am I missing something here that is true across the board? How does the
Mississippi change when the Ohio flows in?

What do you all think?

Eric