Field Study of Ng Tung River: Students’ Workbook 1

Field Study of Ng Tung River

Students’ Workbook

Contents

Page

1. Ng Tung River and the fieldwork sites 2

2. About Ng Tung River 3

3. Enquiry questions 7

4. Fieldwork site A: Hok Tau – Upper Course of Ng Tung River 8

5. Fieldwork site B: Tung Shan Ha 10

6. Fieldwork site C: Tan Chuk Hang 12

7. Fieldwork site D: Kan Lung Wai 14

8. Fieldwork site E: Ma Shi Po 16

9. Fieldwork site F: Wa Shan Tsuen 18

10. How do fluvial processes shape the land? 20

11. How does channel management works influence and alter the

lower course of Ng Tung River?

25

12. How does Ng Tung River help the cultivation of Hok Tau area? 29

Field Study of Ng Tung River: Students’ Workbook 2

1 Ng Tung River and the fieldwork sites

Map 1.1: Ng Tung River and the fieldwork sites

The fieldwork sites (refer to 1.1)

A• Hok Tau - Upper Course of Ng Tung River

(鶴藪 -梧桐河上游)

B • Tung Shan Ha (東山下)

C• Tan Chuk Hang (丹竹坑)

D• Kan Lung Wai (覲龍圍)

E• Ma Shi Po (馬屎埔)

F• Wa Shan Tsuen (華山村)

Field Study of Ng Tung River: Students’ Workbook 3

2 About Ng Tung River

1. About Ng Tung River

Ng Tung River is located in the northeast New Territories. The river catchment covers areas

such as Lung Yeuk Tau (龍躍頭), Fanling (粉嶺) and Sheung Shui (上水). Ng Tung River

is a large tributary of the Shenzhen River (深圳河) System, and its own different tributaries

bare different names, making the delineation of Ng Tung River Catchment complicated.

The river named as Ng Tung River on map originates from the southern slope of Robin's Nest

(紅花嶺) summit (492 m) at an altitude of about 450 m, and flows westward to Fu Tei Au (虎

地坳). However, the actual origin of the main stream of Ng Tung River is from the west of

Wong Leng (黃嶺) summit (639 m) at an altitude of about 580 m. The main stream flows

down the valley on the western slope of Wong Leng and goes into Hok Tau Irrigation Reservoir

(鶴藪灌溉水塘) through Ping Shan Chai (平山仔). It then turns northward to Tan Chuk

Hang (丹竹坑), and then westward merging with the tributary that originates from Robin's

Nest at Ko Po North Tsuen (高埔北村). This river section from Wong Leng to Ko Po North

Tsuen is called Tan Shan River (丹山河) on the map.

The main stream of Ng Tung River merges with other major rivers in the region as it flows

along. A few hundred meters to the west of Ko Po North Tsuen, the main stream merges with

a tributary named Kwan Tei River (軍地河). The main stream continues westward and passes

north of Lung Yeuk Tau before merging with a tributary named Ma Wat River (麻笏河). The

main stream then passes northern Sheung Shui, and merges with two tributaries named Shek

Sheung River (石上河) and Sheung Yue River (雙魚河) near Fu Tei Au (虎地坳). Finally,

the main stream turns north and merges with Shenzhen River.

From a geographical perspective, Tan Shan River, Kwan Tei River, Ma Wat River, Shek Sheung

River and Sheung Yue River are parts of Ng Tung River. However, in this project, Sheung

Yue River is independently featured in another River Journal. Hence, the description and

characteristics of Sheung Yue River are not included here.

Stream order (Strahler’s stream order): 5th order

Drainage pattern: Dendritic

Field Study of Ng Tung River: Students’ Workbook 4

Figure 2.1: The main stream of

Ng Tung River originates from

Wong Leng

Figure 2.2: One of the tributaries of

Ng Tung River originates from

Robin's Nest

Figure 2.3: Lower course of

Ng Tung River

“Rivers@HK Database”

[Ng Tung River > Ng Tung River Location and Catchment >

About Ng Tung River]

https://bit.ly/2Igl3uj

Field Study of Ng Tung River: Students’ Workbook 5

2. River Management

Ng Tung River was formerly known as Fung Kai (The River of Phoenix). It was formed by

a few tributaries including Kwan Tei River, Tan Shan River, Shek Sheung River and Ma Wat

River. The river used to be meandering and flood frequently during the wet season. In the

1990s, large-scale flood control projects were carried out along Ng Tung River in order to

develop Sheung Shui and Fanling. The natural landscape of the river no longer exists.

Irrigation

The fertile land in the river basin attracted a large number of farmers to settle. Some farmers

adopted the "Nanpanshun" farming method by digging ditches at the sides to surround pieces

of farmland. This kind of farming method produced crops of high quality, and at the same

time created wetland habitats that were homes to various animals. However, after the

completion of river training works, water supplied by the river was no longer sufficient to

support "Nanpanshun" farming. Many farmlands had been changed to dry farmlands.

Water Supply Facilities

Kwan Tei River and Tan Shan River originate from Lau Shui Heung and Hok Tau respectively.

In 1968, Lau Shui Heung Reservoir and Hok Tau Reservoir were built to collect river water

which would then be diverted to Plover Cove Reservoir. The two reservoirs also irrigate

farmlands nearby.

Flood Control Projects

In response to the demand for urban development, the middle course of Shek Sheung River

was converted into a culvert in the 1990s. The main stream of Ng Tung River and most

tributaries were also straightened and channelised. Former meanders have been retained as

compensatory wetlands to mitigate ecological impacts due to the works.

Field Study of Ng Tung River: Students’ Workbook 6

Figure 3.4: Hok Tau Irrigation

Reservoir

Figure 3.5: The channelised

Ng Tung River

Figure 3.6: Compensatory wetland

along Ng Tung River

“Rivers@HK Database”

[Ng Tung River > Ng Tung River Location and Catchment >

River Management]

https://bit.ly/2Igl3uj

Field Study of Ng Tung River: Students’ Workbook 7

3 Enquiry questions This field study on Ng Tung River investigate three topics, and the enquiry questions are set as

follows:

1. How do fluvial processes of Ng Tung River shape the land?

2. How does channel management strategy influence and alter the lower course river environment?

3. How does Ng Tung River help the cultivation of Hok Tau area?

Field Study of Ng Tung River: Students’ Workbook 8

4 Fieldwork site A: Hok Tau – Upper Course of

Ng Tung River

Hok Tau Irrigation Reservoir

Hok Tau and Lau Shui Heung Reservoirs, located in the upper course of Ng Tung River,

were built in 1968, with the purpose of collecting and diverting water from nearby streams

to Plover Cove Reservoir. Meanwhile, some river water is used to irrigate adjacent

farmland. This section of the river, named as Tan Shan River, is one of the main tributaries

of Ng Tung River. Tan Shan River is natural with excellent water quality, and it has been

designated by the Agriculture, Fisheries and Conservation Department as an “Ecologically

Important Stream”. The river supports a diversity of flora and fauna. Notably, it provides

an important habitat for dragonflies.

‘My River, My Community’ – WISE Choice

[Site A: Hok Tau – Upper Course of Ng Tung River]

https://bit.ly/2XycGAA

Map 4.1: Field study site at Hok Tau – Upper Course of Ng Tung River

Field Study of Ng Tung River: Students’ Workbook 9

Figure 4.1: Natural stream at Hok Tau Figure 4.2: Black-banded Gossamerwing (Euphaea decorata)

Figure 4.3: Hok Tau Irrigation

Reservoir

Field Study of Ng Tung River: Students’ Workbook 10

5 Fieldwork site B: Tung Shan Ha

In the river section of Tan Shan River located near Tung Shan Ha, river water is used to

irrigate adjacent farmland. Sometimes, Hong Kong Newt could be found in this site. It is

the only tailed amphibian in Hong Kong and is a “protected species” under the Wild Animals

Protection Ordinance. It is also listed as a “Near Threatened” species by the International

Union for the Conservation of Nature (IUCN).

‘My River, My Community’ – WISE Choice

[Site B: Tung Shan Ha]

https://bit.ly/2XycGAA

Map 5.1: Field study site at Tung Shan Ha

Field Study of Ng Tung River: Students’ Workbook 11

Figure 5.1: Ng Tung River

section at Tung Shan Ha

(towards downstream)

Figure 5.2: Irrigation channel

at Tung Shan Ha

Figure 5.3: Hong Kong Newt

(Paramesotriton hongkongensis)

Figure 5.4: Extensive farmland can be

found at Tung Shan Ha

Field Study of Ng Tung River: Students’ Workbook 12

6 Fieldwork site C: Tan Chuk Hang

River flow is steady in Tan Chuk Hang where natural meander could be found. Plants such

as Taro, Parrot Feather and ferns, flourish at river banks and in the channel. This region is

also a dragonfly hotspot and harbours different fish species. However, some river sections

have been channelised to prevent flooding.

‘My River, My Community’ – WISE Choice

[Site C: Tan Chuk Hang]

https://bit.ly/2XycGAA

Map 6.1: Field study site at Tan Chuk Hang

Field Study of Ng Tung River: Students’ Workbook 13

Figure 6.1: Ng Tung River section at

Tan Chuk Hang (towards downstream)

Figure 6.2: Natural meander at

Tan Chuk Hang

Figure 6.3: Parrot Feather

(Myriophyllum aquaticum)

Field Study of Ng Tung River: Students’ Workbook 14

7 Fieldwork site D: Kan Lung Wai

Kun Lung Wai is one of the very well-preserved walled villages built by the Tang clan of

Lung Yeuk Tau. The outer walls were built in 1744. The gate tower serves as the main

entrance to the village, and was restored in 1988. Restoration works on the fallen parts of

the wall and watch towers were completed in 1994. Kun Lung Gate Tower, the Enclosing

Walls and Corner Watch Towers are a declared monument designated by the Antiquities and

Monuments Office. The confluence of Ng Tung River and Ma Wat River is located near

Kan Lung Wai.

‘My River, My Community’ – WISE Choice

[Site D: Kan Lung Wai]

https://bit.ly/2XycGAA

Map 7.1: Field study site at Kan Lung Wai

Field Study of Ng Tung River: Students’ Workbook 15

Figure 7.1: Kun Lung Gate Tower Figure 7.2: The confluence of

Ng Tung River and Ma Wat River

Field Study of Ng Tung River: Students’ Workbook 16

8 Fieldwork site E: Ma Shi Po

A sharp contrast can be observed by comparing the Old and New river channels of Ng Tung

River near Ma Shi Po. To facilitate urban development and control flooding, drainage

improvement works had been carried out at the middle and lower courses of Ng Tung River

mainly in the 1990s and 2000s by which the river channels had been deepened and widened.

Besides, farmland can be found at Ma Shi Po while the local community has organised

guided tours and farmers' market. Located in the North East New Territories New

Development Plan Areas, the landscape at both sides of Ng Tung River may be significantly

altered in the future.

‘My River, My Community’ – WISE Choice

[Site E: Ma Shi Po]

https://bit.ly/2XycGAA

Map 8.1: Field study site at Ma Shi Po

E

Field Study of Ng Tung River: Students’ Workbook 17

Figure 8.1: New Ng Tung River

channel

Figure 8.2: Old Ng Tung River

channel near Ma Shi Po

Figure 8.3: Farmland at Ma Shi Po

Field Study of Ng Tung River: Students’ Workbook 18

9 Fieldwork site F: Wa Shan Tsuen

Environmental mitigation works were implemented amid the drainage improvement works;

for example, the original meanders have been kept and managed as mitigation wetlands, to

alleviate ecological impacts of channelisation works. The old river channel near Wa Shan

Tsuen is an example of a compensation wetland.

‘My River, My Community’ – WISE Choice

[Site F: Wa Shan Tsuen]

https://bit.ly/2XycGAA

Map 9.1: Fieldwork site at Wa Shan Tsuen

F

Field Study of Ng Tung River: Students’ Workbook 19

Figure 9.1: New Ng Tung River

channel

Figure 9.2: Old Ng Tung River

channel

Figure 9.3: The compensatory wetland

near Wa Shan Tsuen

Field Study of Ng Tung River: Students’ Workbook 20

10 How do fluvial processes shape the land?

Study at: Fieldwork site A: Hok Tau – Upper Course of Ng Tung River

Fieldwork site C: Tan Chuk Hang

Fieldwork site F: Wa Shan Tsuen

Enquiry

questions:

How do fluvial processes of Ng Tung River shape the land?

(1) What are different sections of a river?

(2) What landform features are produced at different sections of a river?

(3) How does the energy of a river change at different sections?

Rivers are usually divided into three sections, namely the upper course, the middle course and

the lower course. River energy, amount of water and sediment vary along the river course.

Different landform features are formed by the change of fluvial processes along the three

courses.

1. On Map 10.1 which shows Ng Tung River below,

(a) colour Ng Tung River, Hok Tau Reservoir and Lau Shui Heung Reservoir in blue;

(b) mark the direction of river flow in blue arrows;

(c) mark “upper course”, “middle course” and “lower course” in the appropriate boxes

Map 10.1: Map showing Ng Tung River

Field Study of Ng Tung River: Students’ Workbook 21

2. Visit fieldwork sites A, C and F. Complete the following table.

Fieldwork site A Fieldwork site C Fieldwork site F

Hok Tau –

Upper Course of

Ng Tung River

Tan Chuk Hang Wa Shan Tsuen

Course Upper course Middle course Lower course

Channel gradient

Valley side

Valley shape

Discharge amount

Channel shape and

roughness

Speed of water flow

Load

Amount of energy

Fluvial processes

Erosion

Transportation

Deposition

Landform feature(s)

Field Study of Ng Tung River: Students’ Workbook 22

3. Complete the following annotated diagrams which show the landform feature(s) found at fieldwork sites A, C and F respectively.

Fieldwork site A: Hok Tau - Upper Course of Ng Tung River

Name of landform feature:

Figure 10.1: The annotated diagram showing the landform features

found at Hok Tau – Upper Course of Ng Tung River

Field Study of Ng Tung River: Students’ Workbook 23

Fieldwork site C: Tan Chuk Hang (Middle Course)

Name of landform features:

Figure 10.2: The annotated diagram showing the landform features

found at Tan Chuk Hang

Field Study of Ng Tung River: Students’ Workbook 24

Fieldwork site F: Wa Shan Tsuen (Lower Course)

Name of landform feature:

Figure 10.3: The annotated map showing the formation of the

cut-off at Wa Shan Tsuen

Field Study of Ng Tung River: Students’ Workbook 25

11 How does channel management works influence

and alter the lower course of Ng Tung River?

Study at: Fieldwork site D: Kan Lung Wai

Fieldwork site E: Ma Shi Po

Enquiry

questions:

How does channel management strategy influence and alter the

lower course river environment?

(1) How has the river channel been modified?

(2) How can modifications of the river channel help reduce the risk of

flooding in the area?

(3) How do modifications of the river channel benefit the residents?

Channelisation is a deliberate attempt to alter the natural geometry of the river. Both the

natural river course and channelised river course can be found in the Kan Lung Wai – Ma Shi

Po area.

1. Refer to the map on page 26.

(a) Mark the direction of water flow by arrows.

(b) Which one is the old channel? Which one is the new channel?

Old channel (natural channel):

New channel (channelised channel):

2. Complete the following table on the comparison between the old channel and the new channel.

Channel AB CDE

Old and natural New and channelised

Measure the channel width

Describe the channel width

Channel depth

Sinuosity

Field Study of Ng Tung River: Students’ Workbook 26

Map 11.1: Map showing the old and new channels of

Ng Tung River at Kan Lung Wai – Ma Shi Po area

Figure 11.1: The old and natural channel

Figure 11.2: The new and channelised

channel

Channel AB CDE

Old and natural New and channelised

Channel bed

Capacity to hold water

Velocity

Hydraulic efficiency

Field Study of Ng Tung River: Students’ Workbook 27

3. Complete the Channel Management Works Record Form below.

Locality: Date: Weather:

Section of the river: Upper course Middle course Lower course

Land use along the river:

About the channel management works

Type: Blocks

revetment

Gabion

wall

Concrete

cover

Stone pitching

retaining wall

Description:

Ecological

enhancement:

Grasscrete Grass lining in

gabions

Unlined channel

bed

Shallow pond Wetland Flow deflector

Description:

Intended effects (major purposes):

Aesthetic value: Costing:

Effects on the hydraulic efficiency of the river

Channel width: (find out the width with the aid of a large scale map or by direct

measurement)

Channel characteristics:

Flow volume: Flow speed:

Ecosystem services brought by the management works

Provisioning services (e.g. water supply for irrigation):

Regulating services (e.g. regulating flood water):

Supporting services (e.g. nutrient cycling):

Cultural services (e.g. river park):

Remarks:

Field Study of Ng Tung River: Students’ Workbook 28

4. Group discussion

With reference to the information collected in the field, account for the channel

management works along the lower course of Ng Tung River and their impacts on the

environment. Enrich your discussion by using secondary data.

Field Study of Ng Tung River: Students’ Workbook 29

12 How does Ng Tung River help the

cultivation of Hok Tau area?

Study at: Fieldwork site A: Hok Tau – Upper Course of Ng Tung River

Fieldwork site B: Tung Shan Ha

Enquiry questions:

How does Ng Tung River help the irrigation for the farmlands in

Hok Tau and Tung Shan Ha?

(1) How does the water drain to the farmland?

(2) Is there a sufficient supply of irrigation water?

(3) Is the water quality of the river suitable for irrigation?

1. On Map 12.1,

(a) colour Ng Tung

River, Lau Shui

Heung Irrigation

Reservoir and Hok

Tau Irrigation

Reservoir in blue;

(b) colour the main road

(Sha Tau Kok Road)

in orange;

(c) colour the cultivated

land in green;

(d) mark “X” to locate

where you are.

Map 12.1: Map showing Hok Tau and

Tan Chuk Hang area

Field Study of Ng Tung River: Students’ Workbook 30

2. At fieldwork site B, complete the following tasks:

(a) Complete the annotated diagram below, which shows how river water is irrigated to the field crops.

Figure 12.1: The annotated diagram showing how

river water is diverted to the fields

Field Study of Ng Tung River: Students’ Workbook 31

(b) Conduct a simple test on the water quality of the river.

i) Is there any floating matter, such as foam and

plastic bags, rubbish and oil?

Large amount

Moderate amount

Little or no

ii) What is the smell of the water? Is there any bad

smell?

Strong smell

Moderate smell

Slight or no smell

iii) What is the turbidity of the river water? Is the

river muddy? Can you see through the water?

Very turbid

Moderate

Clear or not turbid

iv) Can you find any animal in the river? Hong Kong Newts Fish

Others:

No

Overall result: Very good Good Moderate Bad Very bad

Is the water quality of the river suitable for irrigation? Yes No

3. At fieldwork site A and B, complete the following tasks:

Field Study of Ng Tung River: Students’ Workbook 32

(a) Walk uphill along Hok Tau Road to Hok Tau Irrigation Reservoir, observe and

explain how Hok Tau Irrigation Reservoir was constructed.

(b) With the help of your teacher, conduct an interview with a farmer in Hok Tau area

by asking the farmer:

(i) how does the irrigation reservoir work?

(ii) is there a sufficient supply of irrigation water?

(iii) how does the supply of irrigation water affect the farmer’s choice of crops and

cultivation methods?