geography internal assessment about stream discharge

Firas A. (ISM IB2-A) – Geography Higher Level

1

Geography Internal Assessment about Stream Discharge

Hypothesis: The discharge of a stream increases downstream. There

will be changes in the stream variables of depth, width and velocity.

1

Name: Firas A.

Candidate Number: 001

1 Illustration shows the Gulp river, obtained from http://www.landscapes.nl/zuid-limburg/


2

Table of Contents

1. Introduction .................................................................................................. 3

2. Fieldwork Method ....................................................................................... 6

3. Individual Description and Analysis ....................................................... 8

Site 1…………………………………………….……………………8

Site 2………………………………………………...………………11

Site 3…………………………………………………...……………13

Site 4……………………………………………………...…………15

Site 5……………………………………………………...…………17

Site 6…………………………………………………...……………19

Site 7……………………………………………………...…………21

Site 8……………………………………………………...…………23

Site 9……………………………………………………...…………25

Site 10……………………………………………………...………..28

4. Overall Analysis and Summary…..………………………..………….31

5. Conclusion………………………………………….………..…………..35

6. Bibliography……………………………………….………….…………36

7. Appendix………………………...…….………….…………..…………37


3

List of Illustrations

Figure 1 – illustrates the drainage basin of the river Maas and the area……………………….5

Figure 2 – showing the ten sites at which measurements were taken………………………….6

Figure 3 – showing the average velocity pattern for site 1…………………………………….8

Figure 4 – measuring the velocity at site 1 using a stopwatch and an orange…………………9

Figure 5 – showing how the depth is greatest at midstream (erosive impact)…….………….10

Figure 6 – showing the average velocity pattern for site 2…………………………..……….11

Figure 7 – series of photographs showing site 2…………………………………………...…11

Figure 8 – cross-section showing depth results obtained for site 2…………………..………12

Figure 9 – showing the average velocity pattern for site 3……………………………...……13

Figure 10 – series of photographs showing site 3…………………………………….………13

Figure 11 – cross-section showing depth results obtained for site 3…………………………14

Figure 12 – saltation in the river………………………………………………………...……14

Figure 13 – showing the average velocity pattern for site 4………………………….………15

Figure 14 – photograph showing site 4……………………………………………….………15


Figure 16 – showing all kinds of possible inflows……………………………...……………16

Figure 17 – showing the average velocity pattern for site 5……………………………….…17



Figure 20 – showing the average velocity pattern for site 6…………………………….……19

Figure 21 – cross-section showing depth results obtained for site 6 ……………………...…19

Figure 22 – photograph showing site 6………………………………………………….……20

Figure 23 – showing the average velocity pattern for site 7……………………………….…21


Figure 25 – photograph showing site 7…………………………………………………….…22






Figure 31 – showing the principle of laminar and turbulent flow……………………………27


Figure 33 – showing the average velocity pattern for site 10……………………………...…29

Figure 34 – cross-section showing depth results obtained for site 10……………………..…29

Figure 34b – photograph showing site 10…………………………………………….………29

Figure 35 – map showing confluence and location of site 10…………………………..……30

Figure 35b – photograph showing confluence at site 10……………………………..………30

Figure 36 – scatter graph showing a positive distance/discharge relationship………….……31

Figure 37 – showing all kinds of possible inflows………………………………………...…32

Figure 38 – average depth from source to mouth……………………………………….……33

Figure 39 – showing average velocity from source to mouth…………………………..……34

Figure 40 – showing width (from bank to bank) …………………………………….………34

Figure 41 – the process of velocity and depth-interaction at a glance (appendix)…...………40


4

1. Introduction

The main purpose of this internal assessment is to test the hypothesis stating that the

discharge2 of a stream increases downstream, and that there will be changes in the stream

variables of depth, width and velocity. In order to be able to test the above mentioned

hypothesis, data was collected at ten selected sites of the Gulp River. The research is expected

to reveal a positive relationship between stream discharge and distance from source, thus

moving further downstream is predicted to result in higher stream discharge. The reason for

such a positive relationship is foreseen to lie within the fact that increased amounts of water,

originating from precipitation, reach the river by means of surface runoff while traveling

further downstream. Moreover, naturally occurring phenomena along the riverbed such as the

deposition of sediment and erosion are expected to result in changes in stream variables of

depth, width and velocity whilst moving further downstream. The Spearman’s rank

correlation coefficient shall be engaged in order to assess the strength of the relationship

between the two variables. The Gulp River is a tributary of the river Geul3 and arises along

the Schwarzenberg near the village of Hombourg. The Schwarzenberg belongs to the northern

Ardennes plateau located in Belgium. In order for the Gulp River to reach the village of

Gulpen in southern Limburg4, it meanders its way through the hilly landscape in a

northwesterly direction. It should be mentioned that the Gulp is a first order stream. It attracts

many tourists whereas at the same the Gulp is essential for farming.

2 In the study of hydrology, the discharge of a river is the volume of water transported by it in a certain amount

of time. Source: http://en.wikipedia.org/wiki/Hydrology 3 Geul is a river in Belgium and the Netherlands. It is a tributary to the river Meuse (major European river, rising

in France). Source: http://en.wikipedia.org/wiki/Geul. 4 Limburg is the southern-most of the twelve provinces of the Netherlands, located in the south-east of the

country. Its capital is Maastricht. This information was obtained from http://en.wikipedia.org/wiki/Limburg


5

In order to put this research into geographical context, the drainage basin5 of the river Maas

and its tributaries is shown in figure 1 below.

Figure 1 – illustrates the drainage basin of the river Maas and the area which this research focuses on 6

5 A drainage basin is an area of land drained by a river and its distributaries

6 Source: http://upload.wikimedia.org/wikipedia/commons/3/30/Meuse_basin.jpg

Geul River

(tributary to

the river

Maas)

Gulp River

(tributary of the

Geul River)

Maastricht

This is the

point where

the Gulp

joins the Geul

(confluence)

Not to scale

Not to scale


6

2. Fieldwork Method

The data collection took place at ten different sites along the Gulp River. The sites where

chosen at an average interval of 3 km in order to ensure sufficient coverage. At each of the ten

sites (figure 2 below) measurements were taken in order to determine the river velocity,

discharge, width and cross-section (depth across river channel). This section of the internal

assessment focuses on explaining what methods were engaged in collecting data and why they

were used.

Site number and name Distance from source (km)

1. Julien Chassis (first site) 0 km

2. De Medaelmolen – Hombourg 3.5 km

3. Nurpo – Teuven 7 km

4. Slenaken 9.5 km

5. Helenahoeve 10.5 km

6. Beutenaken 11.5 km

7. Waterop 14.5 km

8. Pesakerweg 18.5 km

9. Gulpen Pannekokenhuis 20.0 km

10. Gulpen (mouth joins Geul river) 23.0 km

Figure 2 – showing the ten sites at which measurements were taken

First, the cross-section of each of the above listed sites was measured. This was done using a

30 meter tape and a meter ruler. The tape was held tight from the left bank to the right bank,

close to the water surface. Starting from 0 on the tape, the depth of the water in centimeters

was measured. The measurement of the depth was repeated at 0.2 meter intervals, until the

right bank was reached. The results were recorded in a table and the average depth of each

site was calculated using the collected raw data. This method of determining cross-sections is

simple and accurate at the same time. Methods of

straightforward nature are most likely to keep the error

rate at its lowest and therefore produce precise results.


7

Followed by the measurement of the cross-section of each site, the river velocity7 was

determined using a 30 meter tape, an orange and a stopwatch. The orange was found to float

optimally, as 50 percent of the orange remained above the water surface and the other 50

percent below. This ensured realistic velocity results. Starting near the left bank of the river,

the orange was placed in the water - timing how long (in seconds) it actually takes the orange

to travel 5 meters downstream. In total this process was repeated five times near the left bank,

five times at midstream and five times near the right bank of the river – resulting in 15

different values for each site. Occasionally the orange got stuck somewhere in the river and

did not move for a period of time, resulting in odd velocity values on the data table. Finally,

the average water velocity at the left bank, midstream and right bank was calculated using the

acquired data. Afterwards pictures of each site were taken in order to be able to analyze each

site with respect to its natural features, seen in the photograph. The discharge for each site

was calculated as follows: cross-sectional area × velocity.

Measuring the velocity at site 1 using a stopwatch and an orange

7 The velocity of a river is the speed at which the water flows.


8

3. Individual Description and Analysis

Site 1

Distance from source Width

Average velocity

Average depth Cross-sectional area

Discharge

0 km (source) 92 cm 1.45 m/s 1.76 cm 161 cm² 234 m³/s

Velocity measurements taken at the first site resulted in figure 3 below. The reason for the

low velocity (1.45 m/s) can be found considering factors such as little depth and massive

vegetation (increased friction). In order to prove the hypothesis the current discharge of 234

m³/s is supposed to increase further downstream.

Figure 3 – showing the average velocity pattern for site 1

Site 1 - Average Velocity (m/s)

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

River Bank

Mete

r p

er

Seco

nd

Average speed (m/s) 0,65 0,67 0,39

Left Bank Midstream Right Bank


9

As visible in figure 4 below, the left bank (where the 1 is placed) is located on the outside of a

meander, whereas the right bank (where the 2 is placed) is located on the inside of a meander.

Thus, the velocity pattern shown in figure 3 above can be explained by considering the fact

that the water in a river generally flows faster on the outside of a meander (0.65 m/s) and

significantly slower (0.39 m/s) along the inside of a meander.

Figure 4 – measuring the velocity at site 1 using a stopwatch and an orange


10

Graphing the cross-section8 data for site 1 resulted in figure 5 below. The reason for the depth

being greatest at midstream (5 cm) is the fact that this is exactly where the river’s velocity

(0.67 m/s) – and therefore erosive ability – is at its greatest level.

Figure 5 – showing how the depth is greatest at midstream because of the erosive impact of velocity

8 A river cross-section gives depth of the water across the river channel.

Site 1 - Cross-Section

-6

-5

-4

-3

-2

-1

0

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9

Distance across river from left to right bank (m)

Dep

th (

cm

)


11

Site 2


Average velocity


Discharge

3.5 km 96 cm 0.95 m/s 12.16 cm 1167 cm² 1109 m³/s

Figure 6 below shows the average velocity values obtained for site 2. Compared to the

previous site, the discharge has increased 875 m³/s, supporting the hypothesis. The increase in

discharge can be explained considering the 10.4 cm increase in average depth. Greater depth

allows the water to travel faster without having to overcome friction caused by touching the

riverbed. As a consequence of not touching the riverbed, turbulation is kept at its lowest.

Figure 6 (above) – showing the average velocity pattern for site 2

Figure 7 – series of photographs showing site 2

Plenty of

overhanging

vegetation


12

In figure 8 below is it visible that the water is shallowest (10 cm) at the left bank. This can be

explained considering the low velocity (0.13 m/s) associated with the left bank, resulting in

increased deposition of sediment. Thus the results shown in figure 8 below reflect the average

velocity pattern of figure 6 above.

Figure 8 – cross-section showing depth results obtained for site 2


13

Site 3


Average velocity


Discharge

7 km 393 cm 1 m/s 8.9 cm 3497 cm² 3486 m³/s

Figure 9 below shows the velocity pattern for site 3. Compared to previous sites the width

increased about 300 cm and discharge increased about 2000 m³/s, actively supporting the

hypothesis. The significant increase in width is most likely to be the reason for the increase

discharge (more water can be carried).


Figure 10 – series of photographs showing site 3

Overhanging

vegetation

Highest

velocity at

midstream

due to low

friction


14

Graphing the cross-section data for site 3 resulted in figure 11 below. With 18 cm depth near

the right bank the depth increased a great deal compared to the previous sites.

Figure 11 - cross-section showing depth results obtained for site 3

The heavy fluctuations in depth seen in figure 11 above can be attributed to increased water

velocity. Increased water velocity makes the river capable of carrying more sediment. The

sediment in turn erodes the riverbed by means of saltation (figure 12 to the right), eventually

resulting in pot holes.

Figure 12 – saltation in the river9

9 Source: http://earthsci.org/flood/J_Flood04/stream/saltation.gif


15

Site 4


Average velocity


Discharge

9.5 km 315 cm 0.97 m/s 14.82 cm 4668 cm² 4527 m³/s

The classical average velocity pattern can be observed in figure 10 below. The reason for the

velocity being greatest at midstream (0.46 m/s) lies within the fact that at midstream there is

least friction caused by the riverbanks. This allows the water to flow unobstructed and

therefore faster.


Figure 14 – photograph showing site 4

Heavy

under-

cutting

Highest

water

velocity

This 1m deep

pool is the

result of high

water erosion

Slop-off slope

created due to

low velocity

(sediment gets

dropped)


16

Figure 15 below graphically depicts what is described in figure 13 and 14 above. The low

velocity (0.37 m/s) at the left bank resulted in increased deposition of sediment. In figure 15

below it is clearly visible how increased deposition of sediment has lead to a reduction in

depth at the left bank.


The discharge further increased and reached 4527 m³/s. The increased discharge can be

explained considering the fact that increased amounts of water are reaching the river through

inflows while moving downstream. These inflows are depicted in figure 16 to the right.

1. Upstream or tributaries of the river.

2. Surface runoff.

3. Water seeping downhill through soil.

4. Ground water forced into the river through bedrock.

5. Storm drainage system from towns. 10

10

Source: http://www.naturegrid.org.uk/rivers/watercyclepages/riverbasin-stages.html

Figure 16


17

Site 5


Average velocity


Discharge

10.5 km 370 cm 0.45 m/s 18.9 cm 6993 cm² 3146 m³/s

In figure 13 below it is evident that, just like in most cases, at midstream the velocity is the

highest (being 0.22 m/s). Figure 18 below shall clarify the velocity pattern seen in figure 17 –

and point out its main features.




0

0,05

0,1

0,15

0,2

0,25

River Bank

(m/s

)



Slip off slope

resulting in low

water velocity

(0.16 m/s)

This area of flat

ground

alongside the

river is its

floodplain. The

soil here is

particularly

fertile as

nutrients from

the river get

deposited here

The high

average water

speed (0.22 m/s)

resulted in 27

cm depth. (High

erosive ability)


18

Figure 19 below reflects the velocity pattern shown in figure 17 above. Due to the large slip

off slope the water flows with particular low velocity next to the left bank, resulting in

increased deposition and therefore shallower water (at x-axis = 1 in figure 19 below).


The discharge has decreased from 4527 m³/s to 3146 m³/s. The reason for this can be found

considering the large slip off slope to the left bank. The slip off slope resulted in a significant

decrease in depth and velocity. Depth and velocity in turn directly affect the discharge.

However, the general trend remains: discharge is generally increasing further downstream.

Values of depth, width and velocity keep changing while moving downstream.


-35

-30

-25

-20

-15

-10

-5

0

0 0,5 1 1,5 2 2,5 3 3,5 4


Dep

th (

cm

)


19

Site 6


Average velocity


Discharge

11.5 km 446 cm 0.99 m/s 11.3 cm 5039 cm² 4989 m³/s

As evident in figure 16 below the highest velocity (found at the left bank) is associated with

the greatest depth in figure 21 below. This can be explained considering the positive

relationship between velocity and erosive ability. The discharge having increased 1843 m³/s,

agrees with the hypothesis.




20


On the photograph above the long profile of the river is clearly visible. Increased velocity is

leading to more extreme undercutting. In the photograph above the tree on the left bank is

heavily affected by undercutting. The uneven cross-section visible in figure 21 above can be

explained considering the rocks (annotated in the photograph). As visible in the figure 21, this

site contains a number of small potholes.

Severe

undercutting Rocks

obstructing

flow


21

Site 7


Average velocity


Discharge

14.5 km 290 cm 0.25 m/s 18.7 cm 5423 cm² 1355 m³/s

The width has decreased 156 cm compared to the previous site. Also the discharge has

decreased 3634 m³/s. Therefore the relationship between discharge and distance from source

cannot be a perfectly positive one. The Spearman’s correlation coefficient shall illustrate this

later.


The velocity pattern above does not coincide with the cross-section (figure 24) below. The

reason for this might be the unusual pattern of deposition created by the slip off slope (shown

on the photograph below).


22

An exceptionally large slip off slope is clearly visible in figure 24 below. The slip off slope is

not limited to the right bank, stretching over the entire site (see figure 25). This explains the

decrease in discharge and depth.



Huge slip off

slope almost

stretching

over the

whole site


23

Site 8


Average velocity


Discharge

18.5 km 397 cm 0.91 m/s 18.9 cm 6582 cm² 5899 m³/s

The width has increased about 107 cm compared to the previous site. Most importantly, the

discharge increased additional 4544 m³/s. This boost can be attributed to the increase in

velocity and cross-sectional area. These two factors have direct impact on discharge.



24

In the cross-section below the velocity pattern in figure 26 above is clearly reflected. The low

water velocity at the right bank results in increased deposition of sediment load (water

shallow at left bank).



Increased

deposition

due to lower

water

velocity

The river

velocity is the

highest at left

bank


25

Site 9


Average velocity


Discharge

20 km 430 cm 0.77 m/s 8.21 cm 2545 cm² 1959 m³/s

The width further increased 33 cm. However, the average velocity and depth decreased

considerably. This affected the discharge value negatively, resulting in a 3940 m³/s decrease

in discharge. This disagrees with the hypothesis. However, the reasons for the decrease are

due to human interference.

Large amounts of water are being diverted towards the nearby water wheel. The pictures

below show the facilities of the traditional restaurant called “De Pannekoeken Molen” (the

pancake mill). The “Gulp-water-driven” machineries seen in the pictures11

below are still

being used to grind grain for the production of traditional pancakes. Diverting the water has

lead to a 10 cm decrease in depth, 0.14 m/s decrease in average velocity and 4037 cm²

decrease in the cross-sectional area.

11

Source: http://www.depannekoekenmolen.nl/index2.html


26

The average velocity pattern in figure 29 below does not coincide with the cross-sectional

diagram (figure 30). For example, the high velocity at midstream should result in proportional

high depth at midstream (high erosive ability). However, in the cross-section the water is

shallowest at midstream. The reason for this anomaly is inaccurate measuring. The orange

(which was used to determine velocity) got stuck at midstream, resulting in such an odd value.

The reasons for the orange getting stuck were the numerous rocks situated at midstream, seen

in the photograph below (figure 32).




27

As can be seen in the photograph below, the water does not flow absolutely unobstructed.

Rocks in the riverbed cause the water to flow in a turbulent fashion (figure 31 below). This

may explain the uneven cross-section seen in figure 30 above. Turbulent flow encourages the

creation of potholes and braiding.

Figure 31 (above) – showing the principle of laminar and turbulent flow12


12

Source: http://www.tulane.edu/~sanelson/geol111/streams.htm

Vegetation

Rocks causing

turbulent water

flow, small

potholes and

odd velocity

values.


28

Site 10


Average velocity


Discharge

23 km (confluence) 520 cm 1.18 m/s 13.42 cm 5233.8 cm² 6175 m³/s

Site 10 is located where the Gulp joins the Geul (this is also called confluence13

). The left

bank is located on the outside of a meander and is therefore exposed to fast flowing water

with high erosive abilities. This results in high depth at the left bank (figure 34) and heavy

undercutting (figure 34b).


13

Confluence, in geography, describes the meeting of two or more bodies of water. It usually refers to the point

where a tributary joins a more major river. Source: http://en.wikipedia.org/wiki/Confluence_%28geography%29


0

0,1

0,2

0,3

0,4

0,5

0,6

River Bank

(m/s

)




29

The shallow water to the right bank can be explained considering the low water velocity

associated with it. With 6175 m³/s site 10 shows the greatest discharge measured so far. This

may be due to the large amounts of water that reached the river through inflows while moving

downstream.


Figure 34b – photograph showing site 10


-20

-18

-16

-14

-12

-10

-8

-6

-4

-2

0

0 0,5 1 1,5 2 2,5 3 3,5 4


Dep

th (

cm

)

Heavy

undercutting

due to fast

flowing water

(with high

erosive

ability) at the

left bank

Outside of a

meander

(water flows

fastets here)

Overhanging

vegetation

Water flows

slowest on

the inside of a

meander

(more

deposition)


30

Figure 35 (above) – map showing confluence and location of site 10

Figure 35b – photograph showing confluence at site 10

Gulp River

joins Geul

River

(confluence)

Gulp River

Geul River


31

4. Overall analysis and summary

In order to explore the relationship between discharge and distance from source, the discharge

values for all 10 sites were plotted in a scatter graph (figure 36 below). As can be observed by

looking at the scatter graph, a positive relationship between distance and discharge seems to

be present. This means that moving further downstream increases discharge, which proves the

hypothesis stated in the beginning of this internal assessment.

However, as can be seen by the example of sites 7 and 9, the relationship between distance

and discharge is not a perfectly positive one. There are quite a number of anomalies. In the

case of site 7, the reason for the considerable decrease in discharge was the presence of an

exceptionally large slip off slope. This slip off slope, almost stretching over the entire site,

reduced cross-sectional area and average velocity significantly – which in turn had a direct

negative effect on the discharge. In the case of site 9, the exceptionally low discharge can be

attributed to human interference. Large amounts of water have been diverted away from the

river for commercial purposes.

Figure 36 – scatter graph showing a positive distance/discharge relationship

Site 1

Site 2

Site 3

Site 4

Site 5

Site 6

Site 7

Site 8

Site 9

Site 10

0

1000

2000

3000

4000

5000

6000

7000

0 5 10 15 20 25

Dis

char

ge (

m³/

s)

Distance from source (km)

Discharge/Distance Relationship


32

However, even though the relationship between distance and discharge shows some

anomalies, the general positive trend between these two variables remains.

To prove and measure this relationship in statistical terms the Spearman’s rank correlation

coefficient has been calculated. The exact calculations can be found in the appendix.

Spearman Rank Correlation - Ungrouped Data

Statistic Value

Correlation (not corrected) 0.612121

Correlation (corrected) 0.612121

t-Test (n>10) 2.189.453

Degrees of Freedom 8

Critical 2-sided T-value (5%) 2.306.000

Critical 1-sided T-value (5%) 1.860.000

D-square value (calculated) 64.000.000

D-square value (expected) 165.000.000

Standard Deviation 55.000.000

z-Test -1.836.364

Probability 0.065800

Observations (Sites) 10

Thus the corrected correlation being 0.612121 (rs = 0.612) and therefore rs > 0.5 means that the

positive relationship between discharge and distance from source has been proven to be a

relatively strong one.

The reason for increased discharge while travelling downstream was confirmed to be mainly

due to increased amounts of water reaching the river through inflows. These inflows,

increasing the rivers discharge, are depicted in figure 37 below.

1. Upstream or tributaries of the river.

2. Surface runoff.

3. Water seeping downhill through soil.

4. Ground water forced into the river through bedrock.

5. Storm drainage system from towns. 14

14

Source: http://www.naturegrid.org.uk/rivers/watercyclepages/riverbasin-stages.html

Figure 37

http://www.xycoon.com/z_test.htm


33

As can be clearly observed in diagrams 38, 39 and 40 below, there have been significant

changes in the variables of depth, width and velocity while moving downstream – which

supports the hypothesis stated earlier. Figure 40 clearly shows how there is a overall increase

in the bank sizes while moving downstream. This enables the river to carry larger amounts of

water, which is another explanation for the increase in discharge.

Figure 38 (above) – average depth from source to mouth


34

Figure 39 – showing average velocity from source to mouth

Figure 40 – showing width (from bank to bank)

D

0

0,5

1

1,5

0 km 3,5 km 7 km 9,5 km 10,5 km 11,5 km 14,5 km 18,5 km 20 km 23 km

Ve

loci

ty (

m/s

)

Distance in km from source (site 1) to mouth (site 10)

Average velocity from source to mouth


35

5. Conclusion

The main hypothesis of this internal assessment was that the discharge of a stream increases

downstream and that there will be changes in the stream variables of depth, width and

velocity. Through analyzing the visible environment and relating it to collected variables of

depth, width and velocity, the main reasons for changing variables of depth, width and

velocity were successfully identified. Additionally, these variables were found to directly

impact the discharge of a river. Finally, by engaging Spearman’s correlation rank, the

discharge has statistically proven to increase while moving further downstream. In fact, the

positive relationship between distance and discharge was found to be rather significant, as the

Spearman’s correlation rank was calculated to be rs = 0.612.

The main reason for increased discharge while moving downstream was found considering

the increased amounts of water joining the river through tributaries, surface runoff, water

seeping downhill through soil, ground water and storm drainage systems from towns. The

increased amounts of water joining the river mainly resulted in increased width of the river,

which in turn greatly added to the river’s capability of carrying additional amounts of water.

Quite a number of anomalies can be found looking at the graphs and collected data. This can

be attributed to the suboptimal methods of data collection. For example, instead of using an

orange to determine water velocity, a digital water velocity meter could have been used. Such

devices are extremely easy to use and highly accurate. The orange got stuck at several

occasions, leaving odd velocity values on graphs and tables. However, the anomalies are not

always due to suboptimal equipment. Rivers are unpredictable in nature and constantly

changing (dynamic) systems. Human interference (such as the watermill at site 9) causing

unnatural conditions, further add to the number of odd results in charts and graphs.

The validity of the above stated conclusions could have been improved by taking

measurements at more than 10 sites. Taking into account data obtained from 20 different sites

would have provided more reliable results. Additionally, instead of only measuring how the

stream discharge increases downstream, the way the stream discharge decreases upstream

could have been measured. This way more reliable results could have been obtained, as the

same measurement is done twice, which might help to discover mistakes done during the data

collection.


36

6. Bibliography

Software:

Wessa, P. (2007), Free Statistics Software, Office for Research Development and Education,

version 1.1.21, URL http://www.wessa.net/

Information from the Internet:

Canterbury Environmental Education Centre, River Basin Stages, 25/03/2007, URL

http://www.naturegrid.org.uk/rivers/watercyclepages/riverbasin-stages.html

Minnesota State University Moorhead, Calculating Correlation with the Excel

Spreadsheet Program, 02/03/2007, URL

http://www.mnstate.edu/wasson/ed602calccorr.htm

Wikipedia de vrije encyclopedie, Stroomgebied van de Maas, 18/02/2007, URL

http://nl.wikipedia.org/wiki/Stroomgebied_van_de_Maas

Word count: 2432 after subtracting maps, diagrams, graphs and statistical tables and other

supplementary information such as the title page, the contents page and references section.

http://www.naturegrid.org.uk/rivers/watercyclepages/riverbasin-stages.html


37

Appendix


38

The corrected correlation was calculated using the following formulas:

This is the main formula:


39

This is the ranking of the different sites, with respect to discharge:


40

2. Lower

velocity at left

bank

3. Increased

deposition of

sediment at left

bank

4. Sediment

builds up

resulting in low

depth at the left

bank

5. Low x and y-

values on the

cross-section

diagram

1. Left bank on

the inside of a

meander

Factors

determining

river depth

Appendix figure 41 - The process of velocity and depth-interaction at a glance

geography internal assessment about stream discharge

Documents