O-LevelGeographyThe natural environment2217/22 · Oct/Nov 2016 · Q730 Marks

Some students did fieldwork in a small river drainage basin in south west England. The students chose four sites which are shown on Fig. 11 (Insert).

(a)Which two features of the drainage basin are labelled A and B on Fig. 11? Choose from the following: confluence meander source tributary watershed Feature A Feature B[2]
(b)(i)First they measured velocity once at each site using floats, a tape measure and a stopwatch. Describe how they measured velocity.[4]
(b)(ii)When the students returned to school they discussed with their teacher possible weaknesses of their method for measuring velocity. Give two weaknesses of the method. 1 2[2]
(b)(iii)Next the students measured the width of the river channel and the depth of the river at points across the channel. Describe how the students made these measurements and what equipment they used.[4]
(b)(iv)Using their measurements the students drew a cross section of the river channel at each site. The cross section at site 1 is shown in Fig. 12 below. The results of the students' measurements at site 3 are shown in Table 2 below. Table 2 Site 3 measurements Distance from left bank (m) 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 Depth (m) 0.09 0.23 0.38 0.45 0.61 0.78 0.65 0.80 0.67 0.65 0.44 0.38 0.21 0.12 Use the results shown in Table 2 to complete the cross section and complete the shading of the river channel at site 3 in Fig. 13 below.[2]
(b)(v)Describe two differences between the cross sections at site 1 and site 3. 1 2[2]
(b)(vi)The students then calculated the cross sectional area of the river channel at each site. First they had to calculate the average depth of the river. Table 2, on page 18, shows the water depth at the 14 measuring points across the river at site 3. Calculate the average depth at this site.[1]
(b)(vii)Use the data in Table 2 and your calculation in (b)(vi) to work out the cross sectional area of site 3 below. Calculation of cross sectional area at site 3 Cross sectional area = width of river (metres) x average depth of river (metres) = m²[2]
(c)(i)Their results are shown in Table 3 (Insert). Use these results to complete the graph, Fig. 14 below.[1]
(c)(ii)What conclusion should the students make about Hypothesis 1: River discharge increases downstream? Use evidence from Fig. 14 to support the conclusion.[2]
(c)(iii)Look again at Fig. 11 (Insert) and explain the change in discharge downstream.[2]
(d)(i)Fig. 15 shows the completed form for site 3. Use this information to calculate the overall pollution score. Put your answer into Table 4 below. Table 4 Site Pollution score 1 5 2 3 3 4 17[1]
(d)(ii)What conclusion would the students make about Hypothesis 2: River pollution increases downstream? Support your answer with evidence from Table 4.[3]
(d)(iii)Suggest two ways that the students could improve the reliability of their pollution survey. 1 2[2]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2016). The mark or mark type is shown in brackets.

[1 + 1 = 2] A: Confluence
B: Watershed
[1 + 1 + 1 + 1 = 4] Measure set/certain/specific/fixed distance/5-15m (No need for equipment (1)
Put/place/throw float/example or type of float at start of measured distance (1)
Start stopwatch when float is put in (1)
Measure time it takes to travel the measured distance/stop stopwatch or timer when float reaches end of measured distance (1)
[1 + 1 = 2] Only measuring surface velocity/different velocities at different points (1)
Floats get stuck on vegetation/rocks/obstacles (1)
Strong wind may interfere with movement of float/float too light (1)
Only measuring once at each site/didn't repeat/may create anomaly (1)
Measurement will depend on where float is put into river (1)
Start/finish points not clear (1)
Student error with reason e.g. inaccurate timing (1)
[2 x 1 + 1 = 4] Width: (1 + 1)
Measure from one bank to the other/across the river/one student at each side (1)
Keep tape measure taut/horizontal/stretched (1)
Measure perpendicular/at right angles to banks (1)
Depth (1 + 1)
Measure vertically (1)
Equipment to touch river bed (1)
Measure at equal intervals (1)
Measure the wet part of equipment (1)
[1 + 1 = 2] Completion of cross-section; credit each plot – no credit for shading
0.38 m at 5.5m and 0.21 m at 6 m.
[1 + 1 = 2] Cross section is wider at site 3/narrower at Site 1 OR accept Cross section is longer from left bank at Site 3/shorter from left bank at Site 1 (1)
Cross section is deeper at site 3/shallower at Site 1 (1)
Cross section is more irregular/rougher at site 3/smoother or more rounded at site 1 (1)
Cross section is larger at site 3/smaller at site 1 (1)
Cross section has steeper sides at site 3/gentler sides or slopes at Site 1 (1)
[1] Average depth = 0.46m
[1 + 1 = 2] 6.5 × 0.46 (1) Accept use of ▪ or * as multiplication symbols.
= 2.99 m squared (1)
OR 6.5 × answer to (vi) (1)
= correct calculation by multiplication (1)
This last line avoids Error Carried Forward (ECF) penalty
[1] Plot discharge at site 3 = 0.9 cumecs; no credit for shading; ignore if wrong width.
[1R + 1 = 2] Hypothesis is correct/true – 1 mark reserve (1)
Examples of paired data from Fig 4 for 1 mark. Could choose any pair. No need for Units. Must refer to Site numbers
Site 1 is 0.13 but Site 4 is 2.34 (1)
Site 4 is 2.21 higher than Site 1 (1)
For reference allow tolerance as they are referred to the graph not the table i.e.
Site 1 = 0.1-0.14 Site 2 = 0.33-0.39 Site 3= 0.9 only
Site 4= 2.32 – 2.36
If say Hypothesis is partly true or false CROSS HA = 0 and do not mark rest
[1 + 1 = 2] Streams/rivers/tributaries join (1)
Tributaries bring water from other areas of drainage basin (1)
Larger catchment area downstream (1)
[1] Score at site 3 = 10
[1R + 1 + 1 = 3] Hypothesis is generally/to some extent/partly/mostly/somewhat true (1 mark reserve)
Credit figures to show overall increase from site 1 to site 4. (1 Reserve/max)
Credit figures to show anomaly at site 2 (1 Reserve/max)
Example: At sites 1 to 4 the pollution increases downstream from 5 to 17 (1)
However at Site 2 it falls to 3 from 5 at Site 1 (1)
[1 + 1 = 2] Do survey at more sites along river (1)
Take more surveys from different students/pairs/groups/someone else at each site (1)
Work out average for different surveys/multiple times and take average (1)
Same student does all the surveys at all sites – consistency (1)
All surveys to take place at the same time (1)