In times of water scarcity, the Water Code of the Philippin

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Towards integrated water resources
management in the humid urbanizing basins
of Metro Manila and adjoining
regions Leonardo Q. Liongson National Hydra
ulic Research Center University of the Philippine
s Diliman, Quezon City, Philippines First In
ternational Conference on Hydrology
and Water Resources in Asia Pacific Region
APHW2003 Pa-lu-lu Plaza, Kyoto, Japan 13-15 Mar
ch 2003
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Aim of the paper To present the status of compe
ting uses for water resources
in the Metro Manila and adjoining region, and the
needs and prospects for integrated water resourc
es management. Examples of historical time-ser
ies of reservoir releases, rainfall, lake stage
s and salinity are provided to illustrate the
competition among the purposes of water supply,
irrigation, hydropower, aquaculture, fisheries a
nd flood control Outline 1. Introduct
ion 2. Water Supply Development 3. Competition
of Irrigation and Hydropower 4. Competition of
Aquaculture and Fisheries 5. Competition of Floo
d Control 6. IWRM for Improved Governance
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Introduction The natural and soc
io-economic factors of natural resource
degradation, population growth and migr
ation, inadequate institutional and re
gulatory framework in water resource
s management, compounded by the uncert
ainties associated with the effects of
climatic variations and rapid land-use ch
anges, have brought to the fore
the need to achieve and practice
the new integrated methods of managing
water especially for Metro Manila and
its adjoining regions in the biggest isla
nd of Luzon, Philippines.
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Metro Manila is composed of 7 small h
ighly urbanized river SBs (702 sq. km.) which d
rain directly to Manila Bay, and throu
gh Pasig River, provides the only outlet of
one major tributary basin, the urbanized
Marikina River Basin (529 sq. km.) in th
e northeast, and one extensive lake region,
the urbanizing Laguna de Bay Basin with
21 tributary SBs 2300 sq. km.
Lake area 929 sq. km.
Total basin area 3229 sq.km.
in the southeast.
Marikina River
Pasig River
Manila Bay
aaa
Laguna de Bay
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Marikina River Basin (529 sq.km.) and the 21
sub-basins lake of the Laguna de Bay Basin
(3229 sq.km.)
The maps of Marikina River and Laguna de Bay
Basins, which adjoin Metro Manila, showing the r
iver network (left) and the subbasin boundaries
(right). Lake water-quality stations are indicat
ed by Roman numbers I, II, V, IV and VIII.
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• Metro Manila is also adjoined by the Pampanga
  River Basin
  
• (9759 sq. km.) in the north, which includes the
  Mt. Pinatubo
  
• affected sub-basins located some 100 kilometers
  northwest of Manila.
  
• The northern and central parts (islands of Luzon
  and the Visayas)
  
• of the Philippines derive their rainfall yield
  mainly from the
  
• ff. weather systems
• southwest monsoons which originate from the
  Indian Ocean
  
• during the wet season or the northern
  hemisphere summer
  
• (June to September),
• rain intensification afforded by the tropical
  cyclones or typhoons
  
• which cross the country from either the
  western Pacific Ocean or China Sea,
  
• the thunderstorms associated with the
  inter-tropical convergence zone
  
• (ITCZ) which seasonally oscillates between
  north and south of the equator.
  
• In most parts of the region,

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• The humid monsoon climate,
• combined with an active tectonic
• and volcanic history
• of the basins within and
• around Metro Manila,
• has produced the present mixed
• landscape consisting of
• mountainous catchments,
• river floodplains,
• wetlands and deltas
• (with rice paddies and human settlements),
• one major lake
• and a varied geology and hydrogeology or
• aquifers of recent alluvial and
• volcanic origins,
• partly underlain by older

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The suburban expansion of Metro Manila in the
19th century encompasses the network of canals o
r esteros which criss-cross the lowest river d
eltas outside Intramuros but inside the
Pasig River basin, and
follows in the 20th century with
the spread into the higher tectonically-
uplifted tuff-underlain urbanized
river basins, and finally into the
contiguous inland floodplain, lake and
mountainous catchment areas of
formerly rural economies in the basins of the Ma
rikina River and Laguna de Bay.
aa
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• WATER SUPPLY DEVELOPMENT
• Water resources development and management for
• Metro Manila domestic water supply
• started from the modest scale of single-purpose
  city water-supply development
  
• by surface water diversions from nearby
  springs and river sources,
  
• (late 19th century Spanish early 20th
  century American colonial periods).
  
• to the multipurpose river project development
• during the postwar Republican period,
• characterized by a dependence on transbasin
  surface water transfer -
  
• Metro Manila supply capacity 46 cu.m./s or
  4000 million liters per day or MLD
  
• Source the mountainous catchment of the
  Angat River/Reservoir
  
• (a major tributary of Pampanga
  River in the north with
  
• a sub-catchment area of 629 sq
  km.)
  
• There was also a parallel reliance on the
  limited and almost depleted groundwater
  
• resources in the urban areas not served
  adequately with surface water.
  

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Water Supply Development
Angat Reservoir
Novaliches Reservoir
(right) Angat reservoir releases for water supply
and irrigation in an average year 2001. (l
eft) Water-supply sources of Metro Manila from
Angat Reservoir in the north to Novaliches Reser
voir and water treatment plants to the south.
Metro Manila
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• At the close of the 20th century, with the
  pressure of growing population
  
• and expanding urbanization, the planners for the
  water supply of Metro Manila
  
• started to eye (and tap) additional sources such
  as
  
• more surface water transfers
• from other adjacent mountainous catchments,
  and
  
• the potential surface water diversions from
  Laguna de Bay
  
• which is the largest lake of the Philippines,
  
  
• including direct diversions from river
  tributaries themselves,
  
• such as the large Marikina River (presently the
  abandoned river source
  
• during the Spanish and American colonial
  periods).
  
• Water conservation practices have also become
  imperative at this juncture
  
• when more than 50 of the water supply is
  being lost as non-revenue
  
• water due to losses in the distribution
  network ascribed to leaks in
  
• aged pipes, thefts and faulty metering.

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• COMPETITION OF IRRIGATION AND HYDROPOWER
• The theme of integrated water resources
  management or IWRM comes into the fore
  
• because of the existing multipurpose nature of
  the surface water sources earmarked
  
• for existing or possible transbasin transfers for
  Metro Manila water supply.
  
• In the first case, Angat Reservoir in the north
• generates hydro-electricity for the Luzon
  Grid and
  
• also provides water for irrigation of the rice
  lands in the province of
  
• Bulacan where Angat River passes through
  before joining Pampanga River
  
• which drains to northern Manila Bay.
• During times of abundant water,
• the sharing of water for irrigation in Bulacan
  and for water supply of Manila
  
• is fixed by an agreed allocation.
• In either stream, hydro-electricity is
  generated, although higher head
  
• is attained and more energy can be generated
  along the outlet works for irrigation.
  
• In times of water scarcity, the Water Code of the
  Philippines provides that
  

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• COMPETITION OF AQUACULTURE AND FISHERIES
• In the second case for integrated water
  resources management,
  
• namely that of Laguna de Bay,
• the other multipurposes of
• aquaculture and fisheries, flood control,
• as well as irrigation and water supply for
  other cities and provinces
  
• pose competing alternatives
• against the use of the lake water for water
  supply of Metro Manila.
  
• Traditional uses of the lake
• aquaculture, irrigation, power-plant cooling
  water, recreation,
  
• pump-storage hydropower generation, and
  waterway for
  
• minor passenger and cargo traffic.
• More recent uses of the lake
• flood-detention storage of diverted flood flows
  
  
• from a large upstream river (Marikina River)
  through a floodway.
  
• a water-supply source at a limited capacity at
  present.
  

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• The waters of Laguna de Bay are naturally
  brackish,
  
• the lake being connected to Manila Bay by the
  tidally-affected Pasig River.
  
• The salinity of the lake water,
• (maximum during the dry season)
• has fostered the development of
• commercial aquaculture of milkfish
• or bangus, the national fish,
• raised in fish pens and fish cages
• located in the western and
• central portions of the lake.
• Small fishermen also rely on the
• natural salinity for fish catch in the
• open lake areas.
• High salinity
• favorable for aquaculture and fisheries.
• unfavorable as additional treatment costs

Fish pens
Fish cages
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• El Niño months of 1997-1998
• Daily rainfall (in Manila and Los Baños
• stations, north and south of the lake),
• Hourly lake stage,
• Lake salinity in chloride
• concentrations measured
• once a month at five
• lake sampling stations.
• Lake salinity maximum -
• first arrival at West Bay V station,
• nearest the inflow point of Pasig River,
  
  
• last arrival at farthest East Bay II station.
  
  
• attained at the end of after the nine-month
• drought from September 1997 to May 1998.
• Lake stage reached minimum of 10.5 meters
• (which is 0.5 meters above a defined mean
• low sea-water datum of 10.0 meters),

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• COMPETITION OF FLOOD CONTROL
• Flood flows of the Marikina River, joining Pasig
  River
  
• can inundate the lower parts of Metro Manila,
• has to be diverted to Laguna de Bay
• during heavy monsoon and typhoon episodes
• via the so-called Mangahan Floodway
• controlled by an 8-gated weir inlet with
• a diversion capacity of 2400 cu.m/s),
• With the floodflow diversions from Marikina River
  
  
• and its own natural tributary inflows,
• Laguna de Bay becomes a temporary flood
• retention basin during the rainy season,
• so that its higher water level (above Manila
  Bay)
  
• would prevent salinity or seawater intrusion
• unfavorable to traditional brackish-water
• aquaculture and fisheries.
• The recession of the lake water level by

Effective Flood Control Operating System (EFCOS)

of Metro Manila.
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• Concluding remarks on IWRM
• IWRM FOR IMPROVED GOVERNANCE
• The basic problem of governance in the water
  resources sector
  
• recognized to be the major issue to be resolved
  by IWRM
  
• in the Philippines as well as in other
  Southeast Asian countries.
  
• For the Philippines alone, and for Metro Manila
• and adjoining regions in particular,
• IWRM implies that constant dialogues and
  consultations
  
• among the stakeholders in the water sector
  should be
  
• maintained, so that
• feasible solutions to problems and pressing
• issues may develop or evolve.
• separate government agencies had in past
  decades
  
• managed and developed water resources for
• irrigation, domestic and industrial water
  supply,
  
• flood control, hydropower, and other uses,
  often in separate
  

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• IWRM hinges on the river-basin concept in both
  planning and
  
• implementation stages (SEATAC 2000),
• coupled with the multi-stakeholder approach
  through the
  
• practice of
• regular dialogues,
• capacity-building programs,
• advocacy of certain actions,
• information exchange and research
• by and among stakeholders.
• Within the framework of IWRM,
• the issues on basic water policies and reforms,
  and
  
• the issues of competing water uses have begun to
  be dealt with
  
• by the national and regional water resource
  agencies of government,
  
• in regular consultative meetings with other
  stakeholders such as
  
• private industry,
• academe,
• local government units and
• non-governmental organizations (NGO).