The Southwestern New Territories and Kowloon area runs in a wide sweep
from Black Point west of Tuen Mun right through to the eastern end of
Victoria Harbour. Of the five rivers monitored, Tuen Mun River is in
the vicinity of Tuen Mun, Pai Min Kok Stream and Sam Dip Tam Stream
are near Tsuen Wan, Kau Wa Keng Stream is in Kwai Chung and the Kai
Tak Nullah in Kowloon.
[Photo of Map of rivers monitored in the Southwestern New Territories and Kowloon, showing their Water Quality Index gradings in 2005]
The wide geographical range of the Southwestern New Territories and
Kowloon area means that each of these five rivers has quite different
characteristics and historical problems. The Tuen Mun River is a major
watercourse that in the 1980s suffered from a wide range of pollution
sources, including effluent discharged from livestock farms, unsewered
villages, cottage industries, and expedient connections. Further east,
the Pai Min Kok Stream running into the sea at Angler’s Beach was
primarily affected by livestock waste, while the Sam Dip Tam Stream,
closer to Tsuen Wan, was moderately polluted by industrial effluent.
Continuing east, the Kau Wa Keng Stream was largely affected by
expedient connections, as was the Kai Tak Nullah, classified as a
major urban storm channel rather than a stream.
Overall WQO compliance in 1986 stood at 49%. This statistic, as with
all the overall figures cited in this chapter, excludes the Kai Tak
Nullah because, as a storm channel, it is not subject to WQO
compliance. As for the WQI gradings in 1986, only 13% of monitoring
stations were graded ‘Good’ (and none ‘Excellent’). ‘Fair’ gradings
were recorded for 7% of stations, but the bulk of the gradings were
either ‘Bad’ (47%) or ‘Very Bad’ (33%). To reduce pollution in these
watercourses, a number of measures were taken in the 1980s and 1990s
with the aim of improving water quality.
[Photo of Compliance with the Water Quality Objectives in the rivers of the Southwestern New Territories in the 1980s and in 2005]
The major initiatives that led to water quality
improvements were those already discussed throughout this report: the
implementation of the Livestock Waste Control Scheme in June 1988, and
the enforcement of the WPCO as new Water Control Zones were set up.
The North Western WCZ was established on 1 April 1992, covering Tuen
Mun; the Western Buffer WCZ was established on 1 June 1993 and covered
western Tsuen Wan; the Victoria Harbour (Phase I) WCZ was established
on 1 April 1994, covering Tsuen Wan and Kwai Chung; and the Victoria
Harbour (Phase II) WCZ was established on 1 September 1995, taking in
Kowloon. In addition, the implementation of Sewerage Master Plans
across these areas from the 1990s has further helped bring down river
[Photo of Water Quality Index gradings for rivers in the Southwestern New Territories and Kowloon, 1986 and 2005]
By 2005, overall WQO compliance had risen to
88%, and major improvements were also evident from the WQI results. In
that year, 28% of monitoring stations were graded ‘Excellent’ and 66%
‘Good’. Just 6% were graded ‘Bad’, and none were graded either ‘Fair’
or ‘Very Bad’. The turnaround has been very substantial. However E.
coli levels in the area’s rivers and nullah were still high in
2005, especially in the upstream part of the Tuen Mun River (TN1),
where the annual geometric mean was 240,000 cfu/100 mL due to
bacteriological pollution from unsewered villages. The situation
should improve once the Government’s plans to provide public sewers to
the villages in the area are put into effect.
Case study #1: The Tuen Mun River
[Photo of The Tuen Mun River no longer suffers from livestock waste pollution]
The Tuen Mun River is the
major river of the Tuen Mun district, flowing southward from Lam Tei
through a relatively narrow valley into Tuen Mun town centre and past
the Tuen Mun Typhoon Shelter into the sea. It has a total catchment
area of 17 square kilometres.
In the late 1980s the river was severely
polluted, with pollution being worse upstream than downstream. The two
upstream monitoring stations were both graded ‘Very Bad’ at this
period, while the downstream stations were graded ‘Bad’ as they were
further away from the pollution sources.
[Photo of Ammonia Nitrogen concentration (NH3-N)
in the Tuen Mun River (TN1)]
The first problem to be dealt with was
livestock effluent. The Livestock Waste Control Scheme of June 1988
led as elsewhere to a rapid decline in the pollution load from
livestock farms operating in the catchment area. By the early 1990s
most farms had already gone, and by 1996 none remained. The graph
shows the effects of the scheme on reducing typical pollution caused
by livestock waste.
The North Western Water Control Zone was
declared on 1 April 1992, upon which the EPD began enforcing the
provisions of the WPCO in the area. Most of the expedient connections
in Tuen Mun town centre were removed over the next couple of years as
a result, as factories were required to provide proper treatment to
The accompanying graphs show two parameters
relating to industrial and sewage pollution respectively. The first
illustrates the reduction in chromium pollution from industry as a
result of WPCO enforcement in the early 1990s. The second shows
reduction in E. coli levels since the late 1990s following WPCO
enforcement and the completion of various sewerage projects along the
river, such as the construction of a dry weather flow interceptor near
Tseng Tau Tsuen, improvements to the interceptor near Siu Hong Court,
and the replacement of faulty sewers.
[Photo of Chromium concentration (Cr)
in the Tuen Mun River (TN3) ]
[Photo of E. coli levels
in the Tuen Mun River
By 2005, WQO compliance had
risen to 83% and five of the six monitoring stations on the river
achieved gradings of ‘Good’ or ‘Excellent’. One particularly happy
side-effect of the rise in river water quality was the subsequent
improvement of water quality at the picturesque beaches on the coast
near Tuen Mun, which became safer and more pleasant to swim at. One of
these beaches, Castle Peak Beach, had been closed for over twenty
years primarily because of its poor water quality, but was finally
reopened in 2005.
The one blemish on this record was the grading
of the monitoring station furthest upstream (TN1). Its ‘Bad’ grade and
high recorded E. coli levels (240,000 cfu / 100 mL) reflected
the continued presence of unsewered village houses in the vicinity.
The Tuen Mun Sewerage Master Plan and its Review, however, lay out
plans to provide public sewers to over 40 villages around Tuen Mun
over the next decade, so further improvements are expected.
Case study #2: The Kai Tak Nullah
[Photo of The Kai Tak Nullah runs through the densely populated Southeastern Kowloon area]
The urban area of Kowloon, as
on Hong Kong Island, contains few natural watercourses. Most have over
time been covered and converted into storm drains. The Kai Tak Nullah
is also a storm channel situated upstream of the old Kai Tak Airport
in south-east Kowloon. Its catchment includes some densely populated
areas such as San Po Kong, Diamond Hill, Tsz Wan Shan, Wong Tai Sin
and Kowloon City. It suffered severe pollution in the 1980s from large
numbers of expedient connections from factories, raw sewage emanating
from nearby squatter huts, and overflows from old and overloaded
sewers. All six monitoring stations recorded grades of ‘Bad’ or ‘Very
Bad’ in the late 1980s and early 1990s.
Improving the sewerage situation was the first
step in cleaning up the Kai Tak Nullah. Various sewerage works were
outlined in the East Kowloon and North & South Kowloon Sewerage Master
Plans drawn up for the area, and these began to be carried out in the
1990s. They included construction of a number of dry weather flow
interceptors along the nullah to intercept polluted storm flow, along
with the replacement of worn-out and often overloaded sewerage
facilities. This period also saw the clearance of some squatter areas
in the catchment, reducing the quantity of untreated sewage flowing
into the nullah.
The Victoria Harbour (Phase II) Water Control
Zone was declared in 1995, and this in turn enabled the EPD to begin
the task of identifying and removing expedient connections that were
polluting the nullah. The job was by no means easy given the dense
population in the area, the complex tangle of drainage connections and
misconnections, and resistance from some long-standing polluters.
In December 2001 the EPD’s Regional Office (East) launched “Operation Starfish”, establishing a team specifically to address the pollution problems in the nullah. Over the following years, the team systematically combed the catchment for misconnections, carried out investigations, initiated enforcement action against polluters where necessary, and worked closely with the property management sector to improve the situation.
First to be targeted were old residential
buildings and squatter areas. The team carried out three drainage
surveys and four closed-circuit TV surveys covering extensive areas.
Dye-tracing was used to track misconnections back to where they
originated, and the EPD also cracked down on illegal back-lane
dishwashing at food stalls and restaurants. The task required patience
and perseverance, as EPD staff traced misconnections along tangled
downpipes and under manhole covers, facing occasional hostility from
building owners. Operation Starfish ended up identifying some 90
misconnections, and to date it has overseen the rectification of over
90% of these.
[Photo of Chemical Oxygen Demand (COD)
in the Kai Tak Nullah (KN4) ]
Interestingly, the Kai Tak
Nullah has also benefited from a scheme that was primarily designed to
reduce marine water pollution many miles away. The Tolo Harbour
Effluent Export Scheme began in 1995 as a move to improve water
quality in Tolo Harbour by redirecting treated sewage effluent from
the Sha Tin and Tai Po Sewage Treatment Works away from the harbour.
This redirected treated effluent was piped to the Kai Tak Nullah for
discharge where it brought new benefits. The greatly increased flow in
the nullah enhanced water aeration and improved the nullah’s flushing
ability, leading to better water quality overall.
At the end of 2003, the dry weather flow
interceptors that had been installed along the Kai Tak Nullah were
upgraded and turned into an enclosed conduit that helped reduce the
odour problem. Since then, polluted storm flow has been intercepted
and channelled along the enclosed conduit to receive proper treatment
at sewage treatment facilities.
By 2005, the six monitoring stations in the Kai
Tak Nullah had all improved substantially, recording WQIs of either
‘Good’ or ‘Excellent’. These grades were further boosted by the recent
upgrading of the Sha Tin and Tai Po Sewage Treatment Works, which
meant that the exported treated sewage flowing through the Kai Tak
Nullah was cleaner than ever before. Egrets have now returned to the
nullah, which is teeming with fish once again.
Streams in Tsuen Wan and Kwai Chung
[Photo of The Sam Dip Tam Stream has maintained ‘Good’ to ‘Excellent’ water quality in recent years]
The other three rivers monitored in the Southwestern New Territories and Kowloon area (Pai Min Kok Stream, Sam Dip Tam Stream and Kau Wa Keng Stream) are comparatively minor, with small catchments. They have all benefited from the range of measures introduced to reduce pollution over the past twenty years, and achieved WQO compliance rates of between 87% and 97% in 2005. In recent years, all monitoring stations for these rivers have returned WQI grades of either ‘Good’ or ‘Excellent’.
However, the E. coli levels in some of
the monitoring stations remain fairly high (>10,000 cfu / 100 mL), due
to faecal pollution from unsewered premises in the catchments. To
minimise this pollution, sewer connections for some of the premises in
the vicinity of the Sam Dip Tam Stream are in progress, and a public
sewer for the catchment area of the Pai Min Kok Stream is being
constructed in phases, with a scheduled completion date of 2009.