Some students were studying how the characteristics of a river change downstream. They decided to focus their fieldwork investigation on a local river to see if it had some characteristics of a text book example. These characteristics are shown in Fig. 8 (Insert). The students agreed to investigate two hypotheses: Hypothesis 1: The width, depth and cross-sectional area of the river increase downstream. Hypothesis 2: Velocity is greater where the river is deeper.

1. (a)(i)The students wanted to take measurements at six study sites along the river. Suggest why it was important that they took all their measurements on one day.[1]
2. (a)(ii)Suggest two other things they had to consider in choosing their investigation sites.[2]
3. (a)(iii)In preparation they visited a local stream to do a pilot study. Give two advantages of doing a pilot study.[2]
4. (b)(i)The students measured the width of the river channel and the depth of the river at points across the channel. They used the following equipment: : tape measure or rope, metre rule or 30 cm ruler. Describe how the students would make their measurements.[3]
5. (b)(ii)Having made their measurements and recorded them, the students drew a cross-section of the river channel at each site. The cross-section at Site 1 is shown in Fig. 9 (Insert). The results of measurements made at Site 4 are shown in Table 3 below. Table 3 Distance from left bank (m) 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 Depth (m) 0.02 0.08 0.12 0.15 0.22 0.28 0.32 0.38 0.46 0.50 0.46 0.41 Distance from 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 left bank (m) Depth (m) 0.37 0.34 0.28 0.21 0.18 0.16 0.12 0.08 0.06 0.05 0.01 Use the results shown in Table 3 to add the following information to Fig. 10 opposite: • complete the cross-section of the channel, • shade in the cross-sectional area of the river channel.[3]
6. (b)(iii)The students also calculated the cross-sectional area of the channel at each site. Their calculation for Site 1 is shown below. Calculation of cross-sectional area at Site 1 Cross-sectional area = width of river (metres) × average depth of river (metres) = 2.6 x 0.14 = 0.36 sq metres The width of the river at Site 4 was 4.4 metres and the average depth was 0.23 metres. Using this data calculate the cross-sectional area at Site 4 below. Calculation of cross-sectional area at Site 4 Cross-sectional area width of river (metres) x average depth of river (metres)[2]
7. (b)(iv)Describe two differences between the cross-sections at Sites 1 shown in Fig. 9 (Insert) and Site 4 shown in Fig. 10.[2]
8. (b)(v)The summary table of measurements made at the six sites is shown in Table 4 below. Insert your answer from (b)(iii) into the table. Table 4 Site | Distance from source (km) | Width of river (m) | Average depth (m) | Cross-sectional area (sqm) 1 | 2.60 | 2.6 | 0.14 | 0.36 2 | 6.00 | 3.1 | 0.16 | 0.50 3 | 11.40 | 3.6 | 0.20 | 0.72 4 | 14.60 | 4.4 | 0.23 | 5 | 16.40 | 4.4 | 0.27 | 1.19 6 | 22.00 | 7.3 | 0.25 | 1.83 Do these results agree with Hypothesis 1: The width, depth and cross-sectional area of the river increase downstream? Identify a result that does not fit the general pattern.[2]
9. (c)(i)Choose one of these methods and describe how the students would do the investigation.[3]
10. (c)(ii)For the method which you did not choose, give one advantage and one disadvantage of this method.[2]
11. (c)(iii)The students' results are shown in Table 5 below. Table 5 Study site | Average depth (m) | Average velocity (metres per second) 1 | 0.14 | 0.44 2 | 0.16 | 0.51 3 | 0.20 | 0.60 4 | 0.23 | 0.62 5 | 0.27 | 1.20 6 | 0.25 | 1.30 The students plotted these results on a scatter graph, Fig. 11 below. Complete Fig. 11 by adding the results for sites 5 and 6.[2]
12. (c)(iv)To what extent do you agree with Hypothesis 2: Velocity is greater where the river is deeper? Use the information in Fig. 11 to help you to answer.[3]
13. (d)Whilst making their measurements, one observant student noticed how the river valley was different at the six sites. How could the student record these differences during fieldwork?[3]

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