Reach-Scale Monitoring | Advances in Stream Gaging

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Detailed Description

The Arizona Water Science Center demonstrates new methods in Reach-Scale Monitoring to improve accuracy and measurability of high flow events. By installing pressure transducers and using LiDAR to measure topography data, hydrologists are able to simulate flows with two dimensional models which will help better calibrate stream gages. These advances have potential to aid in gathering important hydrologic data in hard to access locations.

Filmed and Edited by Corey Shaw
Music Aritst: Cory Gray, “Technological 1-5”. 
Music provided by


Date Taken:

Length: 00:04:25

Location Taken: Tucson, AZ, US


(digital melody)

- My name's Brandon Forbes.

I'm a hydrologist in Tucson, Arizona.

- My name's Chris Smith.

I'm the data chief for the
Arizona Water Science Center.

- Today we're at Altar Wash

which is an ephemeral
stream in southern Arizona,

and we're surveying with
the ground-based LiDAR

so we could get a full 3D
scan or full 3D topography

of the channel behind us.

What we're doing now is we're
collecting topography data.

We're gonna plug that into the 2D model,

and that's gonna tell us
where we should deploy

our stage sensors in this reach behind me.

Once we have that
deployed, then we're ready

for monsoon season which
usually is gonna start

about mid-July.

So, once that's in place,
the mousetrap's set

and we hope to have some flows

and then get our scientists out

to make direct measurements.

And then we'll have the full suite of data

to really calibrate this model

and see how well this
process is going to work.

- One problem that we have in Arizona,

especially at a gauge like this,

is that we may not have a
flood for three to four years,

maybe even 10 years.

And in between the floods,
we have this vegetation

build up in the channels.

- And one of the things
we look at is vegetation

that's well established.

This is a small stand of desert broom.

It's on the right bank just
downstream of the gauge.

And you can see it's woody vegetation,

but it has the ability to be laid over.

When you have vegetation like this,

it provides resistance to the flow.

And what that does is it raises the stage

for the same amount of discharge

and lowers the velocity.

So it's a key part of
calibrating a 2D flow model,

is determining what this roughness

and what this resistance
actually provides to the flow.

We're back in the office
after the field campaign,

and we have a point cloud made up

of over 12 million points
that we can process

in the computer and
use as a tool to decide

where to put the stage sensors.

Here we are in the point cloud.

We're located just underneath the bridge.

Our stream gauge is located
here on the left bank.

And what we can do is
we can visually zoom in,

decide what kind of
vegetation we want to avoid,

and what kind of banks we would like

to mount the sensors in.

This is a visual tool.

We'll then plug this point cloud

into the 2D flow model,
and that will give us

a hint as to what the
velocities are in the channel

and at what places we can
get the best representation

of what the water surface
would be in a flood.

- We're back at Altar Wash.

We came out with a crew,
and we're gonna install

the posts that hold the CSA sensors.

And so, we just got done
pounding these posts in.

We'll come out here next, and we'll go

and install the sensor itself.

There'll be a little
housing for the sensor,

and we'll bolt it to these.

When you put a gating station out,

you want an accurate rating curve.

You want it to measure the
flow as accurate as possible

because people are making
decisions on that data.

You know, sometimes it's
operating a reservoir.

Sometimes it's a road closure.

Sometimes it's evacuating people.

So, the higher the accuracy for the gauge,

the better decisions that will be made.

If this experiment is successful,

we'll have a more
accurate gauging station.

And if we can make it work here,

we can expand it to other
gauging stations in Arizona.

So this is something
that will really help us

to better understand what the flows are

actually happening during a flood.

- To be able to collect these
different types of data,

especially staged in
many different locations,

and in turn, calibrate discharge

at many different water depths

as we're going to try to do here,

it just allows us to have a
much more robust understanding

of what happens at our sites.

And when floods are occurring,

the data that we serve to the public

and to watershed managers
and emergency managers

will be that much more accurate.

And all that does at the end of the day is

it keeps people safe, and it keeps people

out of harm's way.

And that's really what we want to do.