Water Quality

Question 1

Where can we find hydrometric data? (3)

Answer 1

Can find online - government websites etc.

Pros: standardized, efficient, continuous, high quality

Cons: limited to large rivers, expensive to maintain

Question 2

Where do we measure flow? (3)

Answer 2

Choose a site representative of the reach

Establish a benchmark width

Conduct a cross-sectional survey/measure velocity across to get a range of velocity from slowest areas to thalwag

Question 3

How do we calculate discharge?

Answer 3

We can find the average of the velocities take across the width (m/s), multiply this by the area (m2) (width and depth of that subsection), and this will give us our discharge measurement (m3/s)

Question 4

What is the stream keepers method to discharge measurement? (2)

Answer 4

Stream keepers estimate without a meter by dropping an orange in water at 5 locations across the stream and time it (take average across the stream)

It is not very accurate because water actually flows faster at the surface but this can be accounted for by multiplying velocity by 0.8
(Discharge = average velocitycross-sectional area0.8)

Question 5

What are the types of velocity measurement devices? (3)

Answer 5

Marsh-McBirney - uses a propeller under water to find velocity (not used as often anymore)

Hach - commonly used

Swoffer - calibrated using spin test (blowing on propeller to see when it stops)

Question 6

How to calibrate Hach (7)

Answer 6

Connect sensor to level rod 
Turn on unit 
Go to setup menu 
Select velocity calibration 
Place sensor in still water
Press ok 
Wait for it to calibrate to 0

Question 7

What is another way of measuring discharge? (5)

Answer 7

Install a staff gauge

Used to find a relationship between general water depth and velocity measurements (requires initial velocity measurements)

Water depth is plotted against discharge

Can then figure out future discharge using the graph relationship

May need to go out every year to make sure that the relationship is still the same (e.g. big flood did not change cross-section)

Question 8

How many measurements are necessary for measuring water quality and when might we use them? (2)

Answer 8

Can have many regular measurements for things like monitoring (e.g. drinking water)

Can have one point measurement to detect point-source pollution or during a flood event etc.)

Question 9

What is turbidity? (2)

Answer 9

Degree to which light penetration is blocked because the water is cloudy; measure of sediment suspension

Can use a Secchi disk for more basic measurement or a turbidimeter

Question 10

How do you use the Lamotte 2020we Turbidimeter? (9)

Answer 10

Take samples with vile upside down to avoid water surface
Turn the device on
Select measure, press enter
Insert clean 0.0 blank, aligning line and arrow
Select turbidity with blank, enter
Select scan blank, enter
Wipe down and put your sample in machine
Press scan sample, enter
Repeat 3 times and take the average

Question 11

How do we measure water quality using a YSI meter? (3)

Answer 11

Many different parameters that it can measure
Need to calibrate each parameter you will measure
Be careful with cleaning and storing, cord management, using the probe guard etc.