SAFETY AND TRESPASS

Chapter 3

Define stream discharge

Understand importance of discharge

Understand factors affecting discharge

Measure stream discharge

Know how to use USGS Gauge Stations

Discharge = Flow

The volume of water flowing past a given

point in a given period of time

Cross-Sectional Area

(ft2)

Surface Velocity (ft/sec)

Discharge

(Cubic Feet per Second or CFS)

Definition Factors Importance Measuring Gauge

Stations

A hydrograph

shows variation in

discharge over

time.

Jan 2016

170,000 cfs


Stations

Nov 2015

600 cfs

Anything that affects water velocity and/or

volume.

What affects

stream discharge?

Soil type and

geology

Gradient of

the valley

sides

Type and

amount of

precipitation

Vegetation


Stations

Gradient of valley sides

Vegetation

Soil type/geology


Stations

Type and

amount of

precipitation

Groundwater,

springs,

wetlands, and

tributaries MDC Photo


Stations

0

20

40

60

80

100

1st Mile 5th Mile 10th Mile 15th Mile

Elav

atio

n C

han

ge

Mouth to Headwaters

Stream Gradient

Ozarks

Prairie


Stations

Anything that affects water velocity and/or

volume.

What affects

stream discharge?

Soil type and

geology

Gradient of

the valley

sides

Type and

amount of

precipitation

Vegetation

Channelization Dams

Land use


Stations


Stations

Stormwater entering stream


Stations

Land Use:

Influences volume and

rate of runoff

Channelization:

Increases water velocity

Dams:

Regulate water released

(amount and duration) The Streamkeeper’s Field Guide


Stations


Stations

Physical

Features

Chemistry

Biology

MDC Photo: Greer Spring


Stations

Stream structure

The Streamkeeper’s Field Guide


Stations

Transportation of chemicals and sediment

Concentration of chemicals and sediment

Dissolved oxygen and temperature

MDC Photo


Stations

Determines habitat type and availability

Variety of velocities supports a more

diverse aquatic community



Stations

Plant and Animal

Communities

Biological Cues

Stonefly

Caddisfly Mayfly

MDC Photos


Stations

demands and flows affect water quality

Influences water chemistry and aquatic life

• Helps interpret your data

Quantify and extrapolate data

Idea of severity of problems DNR photo


Stations

A float (whiffle golf ball)*

100-ft. tape measure (10ths of a foot)*

2 sticks/metal stakes

Depth stick (10ths of a foot)

Stopwatch or watch with second hand

10 foot rope * Provided by the Program


Stations

Find a spot in your stream that is:

Straight

Free of obstacles

Noticeable current

Uniform depth (if possible)

**Safety note: If stream

flow is high, do not

measure discharge

DNR photo


Stations

“Header”

information at

top

Instructions for

each step on data

sheet


Stations

Step 1 Step 2 Step 3 Final

Calculation

Discharge Surface Velocity Cross-sectional

Area

Stream Width

DNR photo


Calculation


Area

Stream Width

Place stakes at edges of flowing water on

both sides of stream

Only measure width of flowing water in

stream channel (DO NOT measure dead

water or islands)

0

12 feet


Stations

Move any large

rocks/debris

obstructing flow

Measure stream width

in feet to the 10th of a

foot

(DO NOT measure inches)

DNR photo


Stations

DNR photo


Calculation


Area

Stream Width

Area = Depth X Width

Width

Depth

Need to take

several depths

and calculate an

Average Depth

BUT, stream

depth varies

along bottom

of stream!


Area = Depth x Width


Stations

Use stream width to

determine how many

stream depths you

need to measure

< 20 ft. wide:

measure every 1 foot

> 20 ft. wide:

measure every 2 feet

Width = 12 ft


Stations

Stream depths: measure in feet to the 10th of a

foot, not inches

1.5 feet

One side of your measuring tape is labeled

“TENTHS”, and the other side is “INCHES”.

Make sure you use the TENTHS side!


Stations

Make a depth stick out of a dowel rod using the

Program provided measuring tape

Stand downstream of depth stick

MDC photo


Stations

0.4 0.9 1.2 1.1 1.1 0.9 0.6 0.7 0.3 0.2

Average Depth = 0.7 ft.

7.6 ft. 11 depths = 0.7

ft.

Sum of Depths = 7.6 ft.

0.2


Stations

Cross-Sectional Area = Average Depth x Stream Width

Width = 12 feet

Average

Depth =

0.7 ft.

Cross-Sectional Area =

8.4 ft2

=0.7 ft x 12 ft = 8.4

ft.2


Stations

Stream Depths

Average Depth

Stream Width



Stations

DNR photo


Calculation


Area

Stream Width

Velocity float trial: measure the time it takes for the

whiffle ball to float downstream a certain distance

Start time

Tape Measure

Stop time


Stations

Performing velocity float trials

“Start” “Stop” Drop Ball

Here

MDC Photo


Stations

Stream width < 10 ft 3 velocity float trials

Stream width > 10 ft at least 4 velocity float

trials

Tape Measure

22 sec.

16 sec.

13 sec.

16 sec.

22 sec.


Stations

Float distance

Velocity float trials

Average float time

Average surface velocity

Corrected average

velocity


Stations


Calculation


Area

Stream Width


Stations

Corrected

Average Surface

Velocity

Cross-Sectional

Area

Discharge

(CFS)


Stations

Reminders!

Measure

depths in feet

to the

TENTHS OF A

FOOT.

STREAM WIDTH DEPTHS NEEDED

<20’ depth every 1’

20’-60’ depth every 2’

>60’ depth every 3’

NO ZERO DEPTHS OR

FLOAT TIMES.

Measure flowing water

only.


Stations

3 FLOAT TRIALS

ARE NEEDED

FOR STREAMS

<10’,

and at least

4 FOR STREAMS

>10’

You don’t have to

use a float

distance of 10’

Slow flow?

shorten distance

Fast flow?

lengthen distance Reminders!


Stations

Submit data

sheet even if

flow is too low

or too high to

measure

If wiffle ball

doesn’t move,

flow is too low

to measure!

Flow too low to measure!

Reminders!


Stations

Over 200 gaging stations in MO

USGS website: http://mo.water.usgs.gov/

Mobile site: http://m.waterdata.usgs.gov/

Real-time data

Interactive map

Can use if site is within ½ mile and no other inputs


Stations

Who can define stream discharge?

Why is discharge important?

What factors affect discharge?

What are the 4 steps to measure discharge?

How close must your site be to a USGS Gauge Station to use it for discharge data?

Now, this is how you measure stream discharge…


SAFETY AND TRESPASS

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