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The
watercourse sections located at Pat Heung,
Lam Tsuen, Tai Po Kau and Tai Ho Wan were considered
as of high* ecological value due to their relatively
intact and undisturbed conditions and renowned
for their high biodiversity. The protected
plant species, Nepanthes mirabilis (Pitcher
Plant) was recorded in a large colony near
seepage immediately adjacent to the main river
at Tai Ho Wan during the field visit. Sightings
of the rare fish Ayu (Plecoglossus altivelis)
have also been reported in the streams at Tai
Ho Wan (Chong and Dudgeon 1992; Chong 1993).
Some
of the natural watercourses (eg Site 64c, Sites
65a, b and c and Site 67b) were found to have
been disturbed by some form of pollution as
rubbish and highly turbid waters were observed
during the field surveys. Disturbance due to
development was also observed in some of the
surveyed habitats, eg Sites 64a, 65b and 67b,
where channelisation or modification to stream
banks to reduce flooding locally occurred.
Habitat type or ecological value of these habitats
was adjusted with regard to the existing conditions
observed during field surveys. As defined in
TR1, natural watercourses with substantial
abstraction of water would be classified as
modified watercourses. However, the results
from field surveys showed that where abstraction
of water was observed, the extent of abstraction
was limited to a small section of the river
and thus considered not necessary to re-categorise
the habitat as Modified Watercourse. Nevertheless,
the observed abstraction has been included
for consideration in ecological value adjustment
of the habitat instead. Natural watercourse
habitats where ecological value was adjusted
based on field surveys are shown in Table 7.1h
(see Table G6 of Annex G for details).
| Table
7.1h Rationale for Ecological Value Adjustment
of Natural Watercourse Habitats based
on Field Surveys |
| Site
No. |
Site
Name |
Sub-site |
Ecological
Value After Field Assessment
|
Rationate
for Ecological Value Re-adjustment |
| 64 |
Shap
Pat Heung |
c |
Medium |
Habitat
disturbed by rubbish dumping and turbid
water was observed. |
| 65 |
Pat
Heung |
a |
Medium |
Highly
turbid water was observed. |
| b |
Medium |
Water
was highly turbid and diversion of water
was observed. |
| c |
Medium |
Part
of the stream bank was modified to reduce
flooding. Highly turbid water and diversion
of water was observed. |
| d |
High* |
Upper
reaches very rural and surrounded by steep
wooded valleys. Suitable habitats for dragonflies. |
| 67 |
Kwu
Tung |
b |
Medium |
Highly
turbid and polluted (whitish in colour)
water was observed. A section of the watercourse
was seen undergoing flood protection control
works. |
| 68 |
Fanling |
a |
Medium |
Part
of the stream bank was seen undergoing
flood protection works. Silty water was
observed. |
| 69 |
Lam
Tsuen |
b |
High* |
A
clean, fast flowing river with species
diversity comparatively higher than other
natural watercourses surveyed. Habitat
was found to be free from human disturbance
and a suitable habitat for dragonfly larvae. |
| 70 |
Tai
Po Kau |
a |
High* |
A
clean, fast flowing river with species
diversity comparatively higher than other
natural watercourses surveyed. Habitat
was found to be free from human disturbance
and a well known habitat for wild birds. |
|
72 & 73
|
Pokfulam & Aberdeen |
a |
Medium |
Habitat
located close to residential areas and
a reclamation site. Received discharges
from a drainage channel. |
| 164 |
Tai
Ho Wan |
b |
High* |
A
clean watercourse which forms part of the
SSSI at Tai Ho Wan. Reported to support
high species diversity of freshwater and
brackish water fish in Hong Kong. |
| c |
High* |
As
above |
| a |
High* |
As
above |
| b |
High* |
As
above |
| c |
High* |
As
above |
There
was one sub-site of Natural Watercourse, re-identified
from Modified Watercourse (Site 151a San Tin),
also had its ecological value adjusted after
field verification. The watercourse was downgraded
to medium as it was polluted and covered by
weedy species. The habitat was also affected
by development (flood protection works) and
unlikely to remain natural for long.
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