10 What can we measure in rivers and how can we do it?

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The Practical Components of River Environments
What appears in the specification:
  • Measuring channel features measurement
  • And
  • Measuring water quality

What does this mean in practice?
Regardless of whether you actually carry out these activities, you need to know what to do and what to expect in terms of outcomes. You do not need to carry out all of the activities, even if you have the right situation easily available. But while it will be easier for you to answer the questions if you have done real experience to base it on,. But if you have not got that opportunity, some experience of virtual fieldwork will be a great help.

Water quality: what do scientists measure?
Scientists use many different instruments to determine the quality of water, including Secchi disks (measure water clarity), probes, nets, gauges and meters. But water quality is not just measured by direct sampling. Information can also be derived from aerial and satellite photographs by observing the surrounding environment and by collecting organisms that live in the body of water.

Measurements that help to decide on water quality
The temperature of water can affect it in many different ways. Some organisms prefer cool water, while some like it warm. Most aquatic organisms are cold-blooded. This means that the temperature of their bodies match the temperature of their surroundings. Reactions that take place in their bodies, like photosynthesis and digestion, can be affected by temperature.
It is also important to know that when the temperature goes up, water will hold more dissolved solids (like salt or sugar) but fewer dissolved gases (like oxygen). The opposite is true for colder water.
Plants and algae that use photosynthesis prefer to live in warm water, where there is less dissolved oxygen.
Generally, bacteria tend to grow more rapidly in warm waters. Colder water contains more oxygen, which is better for animals like fish and insect larvae.

Dissolved Oxygen (DO)*
Oxygen is necessary for many aquatic species to survive. This test tells you how much oxygen is dissolved in water for fish and other animal organisms to breathe. Most healthy water bodies have high levels of DO.
Certain water bodies, like swamps, naturally have low levels of DO in the water. This is because decaying matter uses a lot of oxygen during decomposition – or more accurately the micro-organisms that break down the decaying matter use up much of the oxygen in the process.
How does oxygen get in water in the first place? Much of the oxygen in water comes from plants during photosynthesis and also from air as wind blows across the water’s surface. Where the river has a lot of ‘white water’ also has higher oxygen content as the air bubbles mix with water as it tumbles over the rapids and waterfalls
But dissolved oxygen reading can vary greatly over a day. For example on a warm summer afternoon, the water temperature will have increased. As we saw when talking about temperature, the amount of gas water can hold ( the saturation level) is much lower in warm water than cool. This decreases the amount of oxygen that can be dissolved in water. While on our warm afternoon, any plants will have been photosynthesising as the maximum rate and so producing the most oxygen, this cannot remain dissolved beyond the saturation level. Come sundown, the plants stop photosynthesising, so oxygen production ceases, but the respiration (of plants and animals) continues as does decomposition. So that the oxygen levels will be lowest just before dawn, after which the plants start to photosynthesise again
*DO is not an abbreviation widely used in the UK so not one for use in fieldwork assignments or exam paper answers

pH (acidity)
The potential of Hydrogen, also known as pH, is a measure of acidity and ranges from 0 (extremely acidic) to 14 (extremely basic) with 7 being neutral.
Most water is in the range of 6.5–8.5.
Let’s see some examples to compare pH values. Stronger acids have the ability to eat through solid objects if spilled. Liquid bleach has a pH of 11 — this makes it very alkaline. An alkali, just like acids, can burn your skin if they are strong.
Our bodies are made mostly of water which a pH of 7. Things that are close to pH 7 work well with our bodies. The same holds true for aquatic organisms.
If the water becomes too acidic or alkaline, it can kill the organisms that would normally expect to survive - for example acid rain failing in lake has killed fish in many lakes in Scandinavia

Turbidity refers to the clarity of water, or how clear it is. For example on a warm day you may be able to see the bottom of a pond – so the turbidity is low. After heavy rain, the water in mountain streams will be closer to cream of vegetable soup! The turbidity is high.
The turbidity determines how much light gets into the water and how deep it goes. Excess soil erosion, dissolved solids or excess growth of micro-organisms can cause high turbidity on a long term basis. All of these can block light. Without light, plants die. Fewer plants mean less dissolved oxygen. Dead plants also increase the organic debris, which micro-organisms feed on. This will further reduce the dissolved oxygen. No dissolved oxygen means other aquatic life forms cannot live in the water.

After testing these parameters, make a note of the time of year, current weather conditions, cloud cover, air temperature and any other environmental observations that may affect the tests. As you have seen different conditions may affect the results quite markedly.

Water quality: What else do scientists measure besides physical characterises?
Just as nutrients are critical for you to grow (check out what’s inside a box of cereal— essential nutrients), they are critical to plants and animals.
The two major nutrients scientists measure are nitrogen and phosphorus.
The presence of too many nutrients can hurt aquatic organisms by causing lots of algae to grow in the water.
Nutrients can also affect pH, water clarity and temperature, and cause water to smell and look bad.
Where do they come from? Farms are a major source of these. Too many cattle and sheep, entering the water course for a drink, leave behind faeces and urine. These are high in nutrients. If a farmer uses too much fertilizer on ploughed field, this can easily run off into a river during heavy rainfall and add still more nutrients to the water.

Toxic substances
Scientists also test for many harmful (toxic) things like metals, pesticides, and oil. For example, scientists are finding mercury in certain types of fish, especially in lakes and estuaries. Mercury comes from mining, natural sources and air pollution from power plants and incinerators. People are warned not to fish if mercury or other harmful substances are a problem in a stream, lake or bay.

Scientists sample for certain types of bacteria that are found only in the stomachs and intestines of warm-blooded animals and humans. These bacteria are not necessarily harmful, but they usually hang out with some bad characters like viruses and germs that can make you sick. Scientists test for bacteria that indicate that those more dangerous organisms might be in the water.

Biological sampling
Scientists determine the health of waters by taking samples of fish, plants and smaller invertebrates.
Invertebrates include things like snails, worms, and fly larvae. Some of them love to live in water that’s dirty, so if scientists find a lot of those in a sample, they know there’s a problem. Other organisms can survive only in water that’s very clean, so finding those means the water is probably healthy.

Exploring water quality – one option for you
Each year there is a World Water day. As part of this they sell kits for not very much (don’t know how much as I am waiting for an email from them). The site is at http://www.worldwatermonitoringday.org/index.html
The idea is for as many people as possible to carry out simple tests all over the world within a time limited period and log their results onto a web site to help with research. A great bit of mass geographical/scientific research! The tests include pH, temperature, dissolved oxygen measurement and turbidity. Do this on various points in a river near you and that would make a great fieldwork study, especially if some of your sites are down stream of places that are likely to create problems e.g. down stream from where animals can reach the river, of a factory or small village or similar.

The other route – the physical characteristics of the river channel – for virtual users too
The velocity of the river:
Official method:
Use a flow meter to measure the velocity – the modern ones are small propellers attached to a digital read out that works out from the number of revolutions per minutes the propeller spins what the velocity of the river is. You would then take measurement at ¼ , ½ and ¾ of the way across. This would explain why the outside of the bend erodes more due to hydraulic action etc (see Suggestions for activities 1). The flow meter propeller should be at least 15cm below the surface but above the bed of the river.
Unofficial method
What you need- a supply of oranges, a 5 metre or 10 length of … washing line? A stop watch or a watch with a timing mechanism
What you do: Measure the time taken by a float to go a fixed distance – best float – an orange! Bright, it floats its round and so less likely to get caught up on things, its cheap if you loose it. Measure 10 metres of river - using a bit of old washing line perhaps? – drop orange off bridge or from middle of river and use stopwatch to time how long it takes to go 10 metres – repeat at least 3 or maybe 5 times and average
Speed = Distance/time will give you metres per sec.

The angle of fall of the river:
Official method:
This uses a clinometer – basically a protractor with a viewing sight and a string with a weight attached - this is a picture of a homemade one.1.10A_Clinometer.png
To find the gradient, you need 2 poles. From the end of each one measure an exact distance (does not matter what providing they are the same) and put a coloured tape around that point. The end you measure from is the one that goes on the ground.
With one person holding each holding a pole about 2 meters apart at the very edge of the river. 1.10B_Measuring_poles.pngThe one at the lower end has the clinometer – see picture. That is placed on the coloured line on their pole.
They point viewing tube until they can see the coloured marker on the other pole – read off the degrees and you have the slope.

Unofficial method
If you can’t be bother to make up all the bits and pieces, you may like to try this:
Have as long a straight cane as you can find and make a note of how long it is.
Borrow a spirit level and find out how to use it.
Rest the cane up stream on the ground and lower the cane towards the down stream side, holding the spirit level along it. Once the spirit level show that the pole is level, measure the distance above the ground the lower end is and note it down.1.10C_Vertical_drop.png

When you get home use a calculator, to work out the angle like this:
angle = tan(-1) ( height measurement/ cane length) – that is your degrees

The width of a river:
The WIDTH of the river channel can be measured by taking a 30 metre tape measure and stretching it from bank to bank. It should be kept as taut as possible to be accurate. If the stream bank is sloping, keep the tape as near to the water surface as you can so that you can line it up with the bottom of the bank.
1.10D_Width_Vertical_drop.pngYou could use the washing line, mark the width and use any long metal tape to get the width to that point, if your metal tape is too short (a) on the digram below

The depth of a river:
Once the tape measure/rope is stretched across the channel, it is easy to move along at regular intervals e.g. ¼ distance ½ distance and ¾ distance, and measure the DEPTH of the stream using a metre rule. Measure depth in metres e.g. 0.25 for 25 cms. so that width and depth measurements are the same units. (c), (d) and (e) on the picture below
A cheat’s method is to use a garden cane and then measure how far the water came up with your trusty metal rule.
The cross section of the river:
You have the depths at metre distances and you have the widths.
You could
(a) plot on a graph using the same scale for width and depth and count the squares – but you need to know what area each square is first (you may need a bit of help)
(b) Use the trapezium rule – the area of a trapezium, where a and b are the lengths of the parallel sides and h is the distance between them, is ½ (a+b) x h
In your case a and b are the river depths and h is ¼ of the width – so the cross section is
(1st depth + 2nd depth + 3rd depth) x ¼ width
1.10F_Measurment_diag.pngThe calculation
1st trapezium: ½ (0 + d1) x ¼w
2nd trapezium: ½ (d1 + d2) x ¼w
3rd trapezium: ½ (d2 + d3) x ¼w
4th trapezium: ½ (d3 + 0)/ x ¼w
Add them all up: Cross section area: ½(2d1 +2d2 + 2d3) x ¼w
so you get (d1 + d2 + d3) x ¼w

To find the discharge
Is the cross section area x velocity

The size and shape of the bedload:
For this you need a Power's chart (see below)
Note 1 – 3 have definite points whereas 4 – 6 do not
From this chart you can also decide how spherical it is – hence 2 drawing per box – don’t go there!
The size is found by measuring the maximum length – know as the longitudinal axis.
Ideally you should sample 10 rocks/stones/pebbles at each site

Suggestions for activities
1. You may simply take one of these variables, velocity, width, depth, cross section, discharge (although both these 2 of course need 2 or 3 measurements to work them out), Stone size/shape.

Or you might want to go for a different route:
2. You could take measurements across a river on a bend, of depth and velocity and size of bed load on each bank. These measurements could be used to show that water on the outside of a bend for example flows faster than that on the inside. You might to do one in depth study of a meander – looking a velocity, pebble size and shape on the 2 sides, evidence of deposition and erosion – lots of piccies to show what you found.
3. You may want to do velocity and stone shape size in 3 different places – is there a link?
4. Or angle of slope and speed – now that is a controversial one as we discussed when looking at river features, as the speed can sometimes be influence by the bed load as we discussed.

OK So you have decided what data to collect and you have collected it – what now?

This section should briefly outline what the aim of the study was as well as what variables you looked at in your study (ie. how the width, depth, cross-sectional area, channel width, velocity, discharge, gradient and pebbles characteristics or water quality features).

Where the river is (those who are using the virtual data will have this supplied), what the river is like in general description – google maps in aerial are good for this. Etc
Also included in this part is the theory that you will base your ideas on:
Stone size and angularity: what happens to the stones as they are further from the source? (keywords: erosion (explain) (in particular what kind? – explain) and deposition (explain) bedload), so that …..
Velocity: - you need a diagram of a section through the river course – like this one maybe? (the one from the PP for Sept 14 on hydrographs, slide 25)
The explain what generally happens – and any things that might disagree with that and why (keywords: gravity, gradient, bedload)
Angle of fall: explain where a river rises and what the water wishes to do, so where does it go and what happens to the angle of fall (keywords: gradient, gravity) + the diagram in
Width/depth/ cross section: explain why whatever you are measuring is likely to change as it goes down stream (keywords: discharge rate, (explain what that is, tributaries, run-off (from where?))

As you see, depending on what you are measuring this section could be quite long.

Hypotheses / Predictions:
Most of these will start with ‘ The further the site is from the source, the more/less …..

This is because ( summarize what you have written above)

Methods: For the virtual folk, explain the official version of how the data was collected. For the rest, what you actually did.
Include the resources you needed at the beginning and if you are doing pebbles, include a copy of the powers chart. You may include photos of you in action, especially if they help to explain what you did.
Good place to look: http://www.georesources.co.uk/darentfte.htm

Present all your data in neat tables initially.
Then use a range of methods to present your data such as
Bar charts, line graphs, scattergraphs, (these are all available in EXCEL – any problems, let me know – I am a bit of an expert on EXCEL)
And labelled (annotated) photographs
And sketch maps or any other relevant graphical method.

Using the information in the results, go back and restate the hypothesis and see how well you data matches/ does not match. If it agrees, you can go on to say that the data shown agrees with it, showing that … If it disagrees, you need to have an idea as to why that is.

How good was the data collection exercise? What were the good points about it? Did you do enough or could you have done more, time permitting? If you decide you could have done more, what would it have been? How would that have helped?

Great example - thanks Guys

Sorry I could not print them out but adding the pictures single upload by single upload was a chore I really do not have time for!
The first one completed - well done!

Nick Dyson's is another great project - well done!

Alec Christie's - if you have a while and want to see some amazing photographs as well as a complete an assignment as it is possible to do - take a look here.

Callan Cooper's - yet another excellent project of a slightly more manageable size, but full of detail nonetheless.