Rivers (Cambridge (CIE) IGCSE Geography)

The students tested a variety of hypotheses. The two hypotheses chosen by one group were:

Hypothesis 1: The rate of infiltration increases as you go further from the lake.

Hypothesis 2: The rate of infiltration is greater on steeper sloping land

The class of students did their fieldwork along transect lines going down to the shore of the lake. The class was divided into three groups and each group worked on a different transect line. These are shown in Fig. 2.1.

Fig 2.1

To investigate Hypothesis 1, the students identified six fieldwork sites at increasing distances away from the lake. At each site they measured the rate (speed) of infiltration by using the equipment shown in Fig. 2.2.

Fig 2.2

(i)

The students recorded the water level in the plastic tube every minute for 10 minutes. The results of the measurements along transect line A are shown in Table 2.1. Use these results to complete the measurements for site 4 on transect A in Fig. 2.3 below.

Table 2.1

[2]

(iii)

Compare the fall in water level for site 1 and site 5 on transect A.

[2]

(iv)

The students calculated the infiltration rate at each site. Use the data in Table 2.1 to show the calculation which produced the result for site 2 on transect A in the space below.

Infiltration rate = 

         = .....................................

         = 7.2 mm per min

[2]

(v)

The measurements of distance from the lake and infiltration rate at the different fieldwork sites on the three transect lines are shown in Table 2.2. The students plotted these results on a graph, Fig. 2.4. (below). Plot the results at site 6 on transects A and C.

[2]

(vi)

Which transect line agrees with Hypothesis 1: The rate of infiltration increases as you go further from the lake? Tick (✓) your choice below and support your answer with evidence from Fig. 2.4 and Table 2.2.

[3]

 To investigate Hypothesis 2: The rate of infiltration is greater on steeper sloping land, the students measured the slope gradient at each site along the transect lines.

(i)

The results for transect C are shown in Table 2.3 (below). Use this data to plot the result at site 6 in Fig. 2.5 below.

[1]

(ii)

What conclusion would the students working on transect C make about Hypothesis 2:
The rate of infiltration is greater on steeper sloping land? Support your decision with evidence from Fig. 2.5 and Table 2.3.

[3]

Whilst doing their fieldwork, the students also recorded the vegetation found at each measuring site. Their results are shown in Table 2.4 (below). 

How do these results show that the infiltration rate is affected by vegetation?

[3]

The area around the lake where the students did their fieldwork is a popular tourist area. How might people walking in the area affect the infiltration rate? Explain why this would happen.

Students were studying the Bradshaw model which describes how the characteristics of a river change downstream.

The table below summarises some of these characteristics. Add the following characteristics to the correct column in the table.

• amount of load carried by the river

• river discharge

• size of individual load particles

The students decided to investigate two river characteristics included in the Bradshaw model by testing the following hypotheses:

Hypothesis 1: River velocity increases downstream.
Hypothesis 2: The gradient of the river bed decreases downstream.

The students carried out their fieldwork at six sites along the river.

(i)

Suggest three factors the students should have considered in choosing their fieldwork sites.

[3]

(ii)

The students made all their measurements on the same day. Suggest why this was important.

[1]

(i)

The results of the fieldwork are shown in Table 2.1 below.

Plot the results for sites 5 and 6 in Fig. 2.1 below.

[2]

(ii)

What conclusion could the students make about Hypothesis 1: River velocity increases downstream? Support your decision with evidence from Fig. 2.1 and Table 2.1.

[3]

To test Hypothesis 2: The gradient of the river bed decreases downstream, the students used the method shown in Fig. 2.2 below. 

(i)

The results of the gradient measurements are shown in Table 2.1 below.

A student used the method in Fig. 2.3 below to draw the gradient at each site.

Use this method to show the gradient at site 5.

[1]

(ii)

Which conclusion would the students make about Hypothesis 2: The gradient of the river bed decreases downstream? Tick () your decision below and support it with evidence from Fig. 2.3 and Table 2.1.

[3]

When they returned to school the students evaluated their data collection methods. Suggest three improvements they could have made to increase the reliability of the velocity and gradient measurements.

Students in Portugal went to six sites along a local river to do a fieldwork investigation on changes in the river channel downstream. The river which they studied flows 13km from the Sintra Hills to the Atlantic Ocean.

From the alternatives below choose the correct terms to complete the following sentences.

                confluence               mouth            source        tributary          valley       • A river begins at its ..............................          
• A river enters the sea at its ..............................

The students investigated the following hypotheses:

Hypothesis 1: The area of the cross section of the river channel increases downstream.

Hypothesis 2: Average velocity of river flow increases downstream.

The students selected six sites along the river approximately 2 kilometres apart to do their fieldwork.

(i)

In pairs they measured the width of the river channel at each site using a tape measure.
Suggest two things the students could have done to make sure that their results were reliable.

[2]

(ii)

The results of their measurements at each site are shown in Table 1.1.
Plot the result for site 6 on Fig. 1.1 below, which shows how the width of the river channel varies downstream.

[1]

(iii)

At each site the students measured the depth at five points across the channel.
The results of their measurements at each site are shown in Table 1.1.
The students drew cross sections of the channel at each site. These are shown in Fig. 1.2 . Use the information in Table 1.1 to complete the cross section and shade in the river channel at site 4.

[3]

(iv)

The method used to calculate the area of the cross section at each site is shown below.
Insert the correct figures from Table 1.1 in the calculation for site 1 below.

[1]

(v)

The results of the students’ calculations of the area of the cross sections are shown in Table 1.2. To what extent do the results support Hypothesis 1: The area of the cross section of the river channel increases downstream? Circle your decision below and support your decision with evidence from Table 1.2 and Fig. 1.2 (below). 

                                            completely                    partially                 not at all

Table 1.2

 [3]

To investigate Hypothesis 2: Average velocity of river flow increases downstream, the students measured the velocity at each site using the equipment shown in Fig. 1.3. 

(i)

The students calculated the average velocity of flow at each site. Their results are shown in Table 1.2. Plot the result for site 6 on Fig. 1.4 below.

[1]

(ii)

The students’ conclusion was that their results did not support Hypothesis 2:
Average velocity of flow increases downstream. Use evidence from Table 1.2 and Fig. 1.4 to explain why they reached this conclusion.

 [3]

(i)

One student wondered if there was any relationship (correlation) between the area of the river channel cross section and average velocity at the six sites. These results are shown in Table 1.. The student plotted these results on a scatter graph, Fig. 1.5 below.

Use the data in Table 1.2 to plot the results of site 6 on Fig. 1.5 below.

[1]

(ii)

The student decided that there was a partial relationship (correlation) between the area of the river channel cross section and average velocity. Support this decision with evidence from Table 1.2 and Fig. 1.5.

[3]

(iii)

Explain why the area of the river channel cross section may affect average velocity.

 [2]