Visible Pollution
When a river becomes badly polluted, for whatever reasons, it will be evident to someone standing near the river. If you stood next to a heavily polluted river, then you would be able to smell a pungent smell. There would also be visible pollution, for example, a stray bottle floating in the river. We have used a qualitative table to test how polluted a river is. It will be very useful, but to keep it a fair test then we would have to keep the same person doing the marking for the test.
Below is a table that would show us how to grade each river.
Dissolved Oxygen
Oxygen inside a river, or any water could be a big problem. It is one of the most important factors in measuring how clean a river is. It can be expressed in percentages, when there is the most amount of water present then there would be 100% oxygen levels. A high oxygen level can be caused from fertilisers running off fields and into the rivers, and it causes an over growth of water plants such as algae, this algae uses up all the oxygen available, and so the other organisms, like fish are not able to get any oxygen. This process is known as eutrophication.
We were able to get the oxygen levels by: We lowered what is known as an ‘oxygen probe’ into the water. If we left it on land, then it would measure 100% oxygen. It is left in the water for 30 seconds, and we can obtain the reading by looking at a needle pointing to the amount.
We did this test while at each site, because if we had done it later, the oxygen levels could easily have changed, thus giving us a different result. To get a reliable and accurate result each time, we used the same probe, and we lowered the probe to the same depth at each site. We also would leave the probe in the water for exactly the same amount of time.
River Speed and Width of River
Rivers that have a higher discharge levels would be able to dilute much of the pollution and therefore, they would be able to have a lower visible pollution score, and also better water quality. To measure this discharge, we took measurements of the speed and the river width.
We measured the speed of each river by dropping a dog biscuit at a certain point in the river, and we timed how long it took to travel 5m. We did not do a precise measurement for the actual width of the river. Instead we made an educated guess.
To obtain both accurate and results, we used three dog biscuits, timing them each, then we took an average of the three. For as accurate as possible results for the width of the river, the same person should make the estimation.
