10
forest above this. Many of the hill forests are
located in water catchment areas. Peat swamp
and freshwater swamp forests occupy lowlying areas.
Forests play an important role in the hydrological cycle and in maintaining the water balance of watersheds. In Malaysia, forested land
has 38 % water retainability, whereas rubber
estate has 27 % and oil palm estate 16 %.
1.10.4 Freshwater Resources
1.10.4.1 Freshwater Supply
and Demand
The average annual rainfall for the country is
990 × 10
9
megalitres (ML). Out of this,
360 × 10
9 ML returns to the atmosphere as evapotranspiration and 64 × 10
3 ML appears as surface
run-off. Rivers and other forms of surface water
supply about 97 % of the country’s total water
needs, while groundwater accounts for the remaining 3 %. However, in some states like Perlis and
Kelantan, groundwater may contribute signifi -
cantly (30–70 %) to the state’s water budget.
The National Water Resources Study carried
out in 1982 by a team of consultants from Japan
International Cooperation Agency (JICA) produced a master plan for up to year 2000.
1.10.4.2 Water Use and Misuse
Water use in Malaysia can be categorised as
domestic water supply, industrial water supply,
agricultural irrigation, supply to livestock and
wildlife, recreation and aesthetics, hydropower
generation, navigation (transportation), waste
disposal, fl ood mitigation and prevention of seawater intrusion.
In Malaysia today, development on all fronts
is occurring at a rapid pace in order to achieve the
targeted socio-economic objectives. This has
inevitably resulted in adverse changes in the natural environment. Foremost amongst these are
the impacts on the hydrology and ecology of
Malaysian river ecosystems. The Department of
Environment (DOE) has ascertained that a total
of 42 rivers in the country are biologically dead.
The main pollutants are domestic garbage, animal
farm wastes, raw sewage, limestone quarry sludge
and untreated or poorly treated chemical and/
or organic wastes from palm-oil-, rubber- and
wood-based industries.
River otters, swimming ducks, fi shes, prawns,
crabs and other riverine wildlife are now a thing
of the past in some of the rivers. About 65,000 kg
of garbage is estimated to be dumped daily into
the Sungai Kelang (Selangor). About 45 pollutants are known to enter the Sungai Pinang
(Penang). According to the Ministry of Agriculture, Malaysia has 52 freshwater fi sh species
which are of commercial importance. It has been
reported that the Sungai Gombak (Selangor) has,
over the last 20 years, lost about 60 % of its
indigenous fi sh species which once totalled up to
27 species. The reasons cited were excessive land
clearing activities in the watershed area resulting
in river bank erosion and severe siltation. The Sg.
Perak has lost 6 out of the 9 commercially important riverine fi sh species over the last 15 years
(Khoo et al. 1987 ). According to Tualang area,
the pollution of the Sungai Kinta (Perak) and its
tributaries by suspended solids (>300 mg L
−1
) has
reduced by 50 % the cultured prawn harvest in
the last 10 years in this area.
The level of many rivers in the country has
been raised over the years by siltation brought
about by improper watershed development for
various large-scale projects including urban
housing schemes. The consequences include
poor water quality, reduced drainage and fl ash
fl oods. The JICA-proposed fl ood mitigation plan
for Penang Island is estimated to be M$260 million. It involved extensive improvement and
diversion work on the existing St. Penang drainage system and the construction of dual purpose
retention ponds and water pumping stations. The
frequent occurrence of fl ash fl oods has also
promoted the Federal and Perak State Government to allocate M$5 million to alleviate fl ood
problems in the Taiping (Perak) District.
In the case of reservoirs, sediment pollution is
a major cause for concern in Malaysia. It causes
silting of dams. This problem occurs at the
50-ha Ringlet Reservoir in Cameron Highlands
(Pahang) and has promoted National Electricity
Board (Tenaga Nasional) to construct a ‘desander’
1 Introduction
forest above this. Many of the hill forests are
located in water catchment areas. Peat swamp
and freshwater swamp forests occupy lowlying areas.
Forests play an important role in the hydrological cycle and in maintaining the water balance of watersheds. In Malaysia, forested land
has 38 % water retainability, whereas rubber
estate has 27 % and oil palm estate 16 %.
1.10.4 Freshwater Resources
1.10.4.1 Freshwater Supply
and Demand
The average annual rainfall for the country is
990 × 10
9
megalitres (ML). Out of this,
360 × 10
9 ML returns to the atmosphere as evapotranspiration and 64 × 10
3 ML appears as surface
run-off. Rivers and other forms of surface water
supply about 97 % of the country’s total water
needs, while groundwater accounts for the remaining 3 %. However, in some states like Perlis and
Kelantan, groundwater may contribute signifi -
cantly (30–70 %) to the state’s water budget.
The National Water Resources Study carried
out in 1982 by a team of consultants from Japan
International Cooperation Agency (JICA) produced a master plan for up to year 2000.
1.10.4.2 Water Use and Misuse
Water use in Malaysia can be categorised as
domestic water supply, industrial water supply,
agricultural irrigation, supply to livestock and
wildlife, recreation and aesthetics, hydropower
generation, navigation (transportation), waste
disposal, fl ood mitigation and prevention of seawater intrusion.
In Malaysia today, development on all fronts
is occurring at a rapid pace in order to achieve the
targeted socio-economic objectives. This has
inevitably resulted in adverse changes in the natural environment. Foremost amongst these are
the impacts on the hydrology and ecology of
Malaysian river ecosystems. The Department of
Environment (DOE) has ascertained that a total
of 42 rivers in the country are biologically dead.
The main pollutants are domestic garbage, animal
farm wastes, raw sewage, limestone quarry sludge
and untreated or poorly treated chemical and/
or organic wastes from palm-oil-, rubber- and
wood-based industries.
River otters, swimming ducks, fi shes, prawns,
crabs and other riverine wildlife are now a thing
of the past in some of the rivers. About 65,000 kg
of garbage is estimated to be dumped daily into
the Sungai Kelang (Selangor). About 45 pollutants are known to enter the Sungai Pinang
(Penang). According to the Ministry of Agriculture, Malaysia has 52 freshwater fi sh species
which are of commercial importance. It has been
reported that the Sungai Gombak (Selangor) has,
over the last 20 years, lost about 60 % of its
indigenous fi sh species which once totalled up to
27 species. The reasons cited were excessive land
clearing activities in the watershed area resulting
in river bank erosion and severe siltation. The Sg.
Perak has lost 6 out of the 9 commercially important riverine fi sh species over the last 15 years
(Khoo et al. 1987 ). According to Tualang area,
the pollution of the Sungai Kinta (Perak) and its
tributaries by suspended solids (>300 mg L
−1
) has
reduced by 50 % the cultured prawn harvest in
the last 10 years in this area.
The level of many rivers in the country has
been raised over the years by siltation brought
about by improper watershed development for
various large-scale projects including urban
housing schemes. The consequences include
poor water quality, reduced drainage and fl ash
fl oods. The JICA-proposed fl ood mitigation plan
for Penang Island is estimated to be M$260 million. It involved extensive improvement and
diversion work on the existing St. Penang drainage system and the construction of dual purpose
retention ponds and water pumping stations. The
frequent occurrence of fl ash fl oods has also
promoted the Federal and Perak State Government to allocate M$5 million to alleviate fl ood
problems in the Taiping (Perak) District.
In the case of reservoirs, sediment pollution is
a major cause for concern in Malaysia. It causes
silting of dams. This problem occurs at the
50-ha Ringlet Reservoir in Cameron Highlands
(Pahang) and has promoted National Electricity
Board (Tenaga Nasional) to construct a ‘desander’
1 Introduction