A PROGRAM FOR

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HAROLD E. HEDGER INTERNATIONAL COOPERATION ADMINISTRATION

NATIONAL ECONOMIC COUNCIL REPUBLIC OF THE A PROGluM FOR

FORMULATION OF PLANS FOR MULTI-PURPOST DEVELOPM4ENT

OF WATER RESOURCES OF THE PAMPANGA, AGNO,

ILOG-HILABANGAN, BICOL, AGUSAN AND BASINS

OF THE PHILIPPINE ISLANDS

Prepared by

HAROLD E. HEDGER Consultant INTERNATIONAL COOPERATION ADI'TISTRATION

F or

NATIONAL ECONOMIC COUNCIL Republic of the Philippines

Manila, Philippines June, 1961

D 5421 A PROGRAM FOR THE FORMULATION OF PLANS FOR MULTI-PURPOSE DEVELOPMENT OF WATER RESOURCES OF THE PAMPANGAs AGNOs COTABATO, ILOG-HILABNGAN;, BICOL, AGUSAN AND CAGAYAN RIVER BASINS OF THE PHILIPPINE ISLANDS

Harold E. Hedger Flood Control Consultant June 1961

At the urgent request of President Garcia, resulting from

serious flood losses in the Pampanga and Basins in

Central in iAugust 1960, a cooperative project was sub­

mitted to ICA/W by USOM/Philippines with the concurrence of the

Philippine National Economic Council which originally con­

templated review and recommendation by flood control consultants

of flood control plans heretofore prepared by Philippine Government

agencies for protection of this area, but which was later expanded

to include investigation of the desirability of combining flood

control measures with other types of water utilization, such as

hydro-electric power generation, water supply, etc. The program was also expanded to include the basins of the Cotabato, Ilog-

Hilabangan, Bicol, Agusan and Cagayan , the locations of which are shown on the accompanying map. It was tentatively expected to involve the services of a 5-man team of experts over a period of 18 months, plus the supply of certain commodibies and services, all at an estimated cost of about 4,4OOOOO.

The appointment of a short-term flood control consultant was authorized by ICA/W for the purpose of conducting a pilot -2 ­

survey of the basic data, plans and other material available

for review, and the formulation of a definite action program

for the subsequent guidance of a consulting team. The fol­

lowing report presents this consultant's findings and recom­ mendations.

Initial review of the problems involved was accomplished

by study of hydrologic data and analyses, hydraulic plans and

economic material developed by the River Control and Drainage

Section, Division of , Bureau of Public vWorks (BPW);

followed by consultation with officials and engineers of the

National Power Corporation (NPC), National Waterworks and

Sewerage iuthority (NWSA) and with various sections of the BPW, including River Control, Irrigation, Ground-Water

Investigation and Hydrology Sections and the Irrigation

Service Unit of the Department. Field inspections of all of the basin watersheds was also undertaken to insure adequate understanding of the many problems involved.

Availability of Data

The availability of basic data, bydrologic studies, mapping, surveys and engineering data for water resources planning, as disclosed by this review is presented as follows: Basin -

Maps: Aerial photos and mosaics (controlled) of the basin, scale 1:40,000. - 3 -

Topographic, general, scale 1:1,000,000 contour

interval 150 m.

Topographic, general, scale 1:250,000 contour

interval 100 m.

Topographic, general, scale 1:50,000 contour

interval 20 m.

Topograchic, special, Swamp, scale

1:90,000 contour interval 1 m.

Topographic, special, of sites on Angat,

upper Pampanga and Talavera Rivers.

Rainfall records: from 19 stations within the basin,

all standard ;ages; length of records,

from 4 years to a maximum of 30 years, broken in continuity.

Runoff records: from 32 automatic recorders and 23

staff gages, data published 1953-54

3nd 1956-57, unpublished 1957 to date.

Suspended sediment data obtained at 9 points during last 2 years.

Some recent data on evaporation, salinization and ground water level is available.

Field surveys, with location plan and cross sections are

available for Rio Chico, Pampanga and Parua River Channels.

Field surveys, analysis and report on flood damages at­

tributable to the 1937, 194, 1950 and 1960 floods are available, with computation of average annual damage.

Flood Control studies made to date include:

Isohyetal maps and charts for major storms of record;

for mean annual and monthly precipitation, with

frequency analysis, and for estimated 100 year 1-day

through 7-day rainfall.

Derivation by unit hydrographs, infiltration capacity

curves, and per cent runoff curves of the design

maxidmum storm for Pampanga basin; and for Rio Chico and Angat Rivers separately.

Flood routing studies of basin runoff assuming natural

storage in San Antonio and Candaba Swamps only, and

also with storage assumed at Angat and other proposed damsites.

Alternative plans and estimates for conveying design

maximum storm from Candaba Swamp to Manila

Bay, with and without regulating storage at .

Complete hydrology, design, plans and construction data for proposed Angot dam and hydro-electric oroject.

Preliminary studies for proposed Dam.

Data on irrigation systems operated and proposed in basin.

Data on water supply systems in basin. Reports on "Rainfall and Runoff in Central Luzon" and

on "The Pampanga River Flood Control Project" by

A. A. Villanueva and A. B. Delefa; also "Report on

Surface Water Supply of Central Luzon" by Tomas Saddam.

Agno River Basin

Maps: Aerial mosaics (controlled) of watershed, scale

lil5,000 and 1:42,000.

Aerial mosaics (controlled) of Viray-Dipalo River

System, scale 1:30,000.

Topographic maps, scale 1:1,000,000 contour

interval 150 m.

Topographic maps, scale 1:400,000.

it it " 1:250,000 contour

interval 50 m.

Topographic maps, scale 1:50,000 contour

interval 10 m.

Location plan and profile of Agno River, San

Manuel to Gulf.

Rainfall date: from 19 stations with standard gages

and 1 with automatic recorder; length

of records, from 7 years to maximum of

52 years, broken in continuity.

11 standard gages are located within

the wutershed, the others are located - 6 ­

around the perimeter. Runoff data: from 6 staff gages and 3 automatice recorders.

Length of record - from 1 to 16 years,

broken. Maximum flood heights for 10

major flood periods.

Suspended sediment s3mples have been taken at 2 points for period of about 21 years.

Some ground water elevations and evaporation data are available.

Field surveys, analyses and estimates have been made of

flood damage during 1935, 1937, 1947, 1948 and .1960

flood periods, also estimate of average annual damage

"Report on Surface 'later Supply of Central Luzon" by

Tomas Saddam and report on "Rainfall and Runof* in

Central Luzon" by A. A. Villanueva and A. B. Delefla.

Flood Control Studies:

Isohyetal maps of mean annual and monthly rainfall in

watershed with expectancies computed for 5, 10, 20 and 50 year frequencies.

Isohyetal charts of watershed showing design storm

pattern for 1-day through 7-day rainfalls. Same

for Agno River above San Manuel, and for River. - 7 -

Derivation of design maximum storm discharge from

unit hydrographs for Agno River at San Manuel and

Wawa, and for .

lydro-electric studies:

Hydrology, design and construction plans and other

data for existing projects at Ambuklao and Binga

and preliminary studies for proposed projects at

Tabu, Tayum, Kalipkip and Lubas sites.

Irrigation studies relative 6 existing and proposed

systems in this basin.

Water supply data concerning municipal and barrio

systeims, both existing and proposed.

Cotabato River Basin (Rio Grande de ) - Mindanao

laps: Aeri3l mosaic (uncontrolled) of basins, scale

1:16,000 and 1:35,000.

Topographic, general, scale 1:1,000,000 contouir interval 150 m.

Topographic, general, scale 1:250,000 contour

interval 100 m.

Topographic, general, scale 1:50,000 contour

interval 20 m.

Topographic, general, (Mindanao) scale 1:200,oc 0 1:600,000 1:50,000 Topographic, special,,of City of Cotabato in progress. - 8 -

Rainfall records: from 14 standard gages, 7 of which are within the watershed; length of

records from 6 years to maximum of

4 years, broken in continuity.

Runoff records: from 8 automatic recording and 12

staff gag-s located on various

; length of records from

1 yr. to maximum of 11 years, broker

Field surveys: Profiles and cross-sections of the

Pulangui and 1aridagao

Rivers and cross-sectioning of lower

Cotabato River now in progress; also

profile and cross-sections of 7 pro­

posed cut-off channels and one pro­

posed floodway.

Flood damage surveys, analyses and estimates of damage

during 1955, 1956 and 1958 flood periods with estimates

of average annual damage.

Flood control studies:

Isohyetal maps of Mindanao for maximum 1-day through

h-day rainfalls for major storm periods of 1955 and 1956.

Depth-area curves for 1955 and 1956 major storms.

For Pulangui River, at Pikit bridge - discharge

rating curves, rainfall hydrographs, computation - 9 ­

of maximum probable discharge by unit hydrograph and

depth-area methods, rainfall frequency curves for

maximum 1-day through 7-day periods.

Hydro-electric studies: preliminary only, for 1 large

and 1 small proposed projects on Pulangui River.

Several other sites due for investigation.

Irrigation studies relative one system under construction

and 8 proposed systems within this basin.

Water supply data as to several waterworks systems and

numerous barrio wells and springs. log-Hilabangan River Basin - Negros Occidental

Maps: Aerial photos and mosaic (uncontrolled) of the

basin, scale 1:40,000.

Topographic, general, 1:1,000,000 contour

interval 150 m.

Topographic, general, 1:250,000 contour

interval 100 m.

Topographic, general, 1:50,000 contour

interval 20 m.

Topographic, special, flood plain and irrigation

maps of Ilog and Hilabangan Rivers.

Rainfall records: from 4 standard gages all of which

are located outside the watershed;

length of records from 3 years to max­

imum of 43 years, broken in continuity. - 10 -

Runoff records: from 6 automatic recording and 4 staff gages, length of records vary

from 4 to maximum of 7 years, broken.

Suspended sediment at one station from 1956 to date.

Field surveys (plotted) of location and cross-sections

of lower Ilog River, of Hilabangan River, Bungol River and Salong Creek; also of proposed diversion and cut­ off channels.

Flood damage surveys; estimates of damages during flood

periods of 1949, 1950, 1951 and 1952, with estimate

of average annual losses.

Flood control planning: Isohyetal maps of maximum 1-day

precipitation during major storms of 1939, 1949 and

1952; computation of 1-day rainfall depth-area curves

for these storms, rainfall hydrographs for period of

rainfall records; and computation of maximum discharge

and backwater data for lower Ilog River. An overall flood control scheme consisting of levees, by-pass

channels, and channel straightening has been adopted

and hydraulic design prepared.

Hydro-electric planning: Field exploration has been

undertaken of 3 damsites on Ilog River upstream from

with Hilabangan River, but foundation con­

ditions have been found unsatisfactory, particularly

at the lower two sites. Further consideration is - 11.­

being given to a site on the Ilog River.

:rrigation planning: Preliminary studies have been

made of one small system in this basin.

rater supply planning and several small waterworks

systems and barrio supplies (wells and springs) are

in operation.

Bicol River Basin

laps: Aerial photos and mosaic (uncontrolled)

scale 1:40,000.

Topographic, general, scale 1:1,000,000 contour

interval 150 m.

Topographic, general, scale '1:250,000 contour

interval 100 m.

Topographic, general, scale 1:50,000 contour

interval 20 m.

Topographic map of , to

San Miguel Bay, scale 1:4,000 and 1:20,000.

Watershed maps, scale 1:4,000 and 1:20,000.

Rainfall records: from 7 standard gaging stations of

which 6 are located within the water­

shed; length of records varies from

4 yr to maximum of 34 years, broken

in continuity.

Runoff records: from 9 automatic and 17 staff gage

stations; length of records varies - 12 ­

from 1 yr. to maximum of 11 years. Field surveys (plotted) of Bicol River from Lake Bato

to at , showing location

plan, profile and cross-sections of river channel and

proposed cut-offs.

Flood damage surveys of flooded areas and estimates of flood damage during floods of 1947, 1952 and 1956;

and estimates of average annual flood losses.

Flood control planning: Isohyetal maps of the basin

during maximum 1-day through 4-day periods of major

storms of record. Analysis by Theissen's method of

1-day through 7-day rainfall during major storms

over watershed; frequency and depth area curves for

1-day through 5-day maximum rainfall; computation of, maximum probable discharge at mouth of Bicol River

through development of unit and compound hydrographs.

A scheme for flood control has been adopted for

Bicol River from Lake Bato to the river mouth through

a proposed system of levees, revetments, channel

straightening and dredging, and bridge reconstruction

involving channel length of 66 kms. and total esti­

mated cost of about Y10,500,000. Also certain cost­

benefit studies have been made.

Hydro-electric planning: one small existing plant at

Lake Buhi suitable for some expansion. No other

projects under consideration. - 13 - Water Supply planning: several waterworks systems and

barrio supplies (wells and springs) in operation.

Agusan River Basin

Maps: Aerial photos (controlled) of major portion of

watershed, scale 1:40,000.

Topographic, general, scale 1:1,000,000 contour

interval 150 m.

Topographic, general, scale 1:250,000 contour

interval 100 m.

Topographic, (lower reach only) scale 1:50,000

contour interval 20 m.

Watershed maps.(from C&GS map) 1:500,000 no contours.

Rainfall records: from 8 standard gages of which 1 is

located within the watershed; length

of records from 5 years to maximum or

49 years, broken in continuity.

Runoff records: from 2 automatic recording and 3 staff

gage stations; length of records, fron

3 years to maximum of 6 years.

Flood control planning: Very little to date; no hydro­ logic studies.

Hydro-electric planning: 1 small plant now operating; no others under consideration.

Water supply planning: Very little data available.

Cagayan River Basin

Maps: Aerial photos and mosaic (uncontrolled) of major

portion of watershed, scale 1:40,000. - 14 -

Topographic, general, scale 1:1,000,000 contour

interval 150 m.

Topographic, general, scale 1:250,000 contour

interval 100 m.

Topographic, (western portion only) 1:50,000

contour interval 20 m.

Watershed map (C&GS) 1:50,000.

Rainfall records: from 1 automatic recording and 9

standard gage stations of which 4 standard gages are located within the

watershed; length of records, from 14

years to maximum of 52 years, broken

in continuity.

Runoff records: from 14 staff gages and 5 automatic

recorders; length of records 2 years

to 9 years.

Field surveys (plotted), location plan, profile and

cross-sections of Cagayan River from mouth to .

Flood damage surveys and estimates of damage during

floods of 1954, 1955, 1956 and 1957, with estimates

of average annual flood losses.

Flood control planning: very little to date; no hydro­

logic studies.

Hydro-electric planning: sizable projects under consi­

deration on tributaries Chico, Siffu and Magat Rivers. No existing projects.

Water Supply planning: a few waterworks system and various barrio supplies (wells and springs) in operation. - 15 -

Planning Responsibilities

Responsibility for the planning, construction and operation of public-owned electrical power generating projects, both hydro­ electric and thermal, is assigned by the Philippine Government to the National Power Corporation, an independent agency. Such work is financed by revenues from the sale of power, and by loans or sale of bonds secured by revenues. NPC has an engineering staff experienced in performing hydrologic studies, field and geologic exploration of damsites, design and economic evaluation of of considerable height, and has recently undertaken the exploration of several new damsites for hydro-power development. It is the only government agency fully equipped to handle the exploration of sites and design of high dams at this time. Until recently its investi­ gations have been confined to hydroelectric development only, but were extended to consideration of additional storage for water supply, irrigation and flood control at the proposed Angat and

Marikina Dams.

The National Waterworks and Sewerage Authority is charged with the planning, construction and operation of public-owned waterworks and sewerage systems in the Philippines and with supervision and technical guidance in the development of various barrio (village) water supplies, which at present usually consist of supply points fed by springs, wells or diversions from streams. NWSA is also a government agency and finances its operaticns by revenues received from the sale of water and fr-n regular charges made for - 16 ­

sewerage operations. So far reservoir storage created by

sizable dams has been provided only for the Manila and Suburbs

water system, but present plans propose an allocation of storage

capacity in Angat and Marikina Reservoirs when these multi­

purpose dams are completed. NwSA is considered to be capably

staffed for its functions with respect to engineering supervision.

The Bureau of Public Works, an agency of the Department of

Public Works and Communications, is responsible for the planning,

construction and operation of all public-owned gravity irrigation

systems, these functions being delegated to the Irrigation Section

of the Irrigation Division, and for the planning, construction

and maintenance of all public-owned flood control works, delegated

to the River Control and Drainage Section of Irrigation Division.

Other functions assigned the Irrigation Division include the

investigation and protection of ground water resources of tho

Philippines, delegated to the Ground Water Section, and the

collection of streamflow and other basic data required for planning

of BI projects and not obtainable from the Weather Bureau, delegated to the Hydrographic Section. Navigational problems connected with river channel improvements and maintenance are of concern to the River Control Section, as are problems of sedimentation, salinization, etc. affecting river channels.

Funds for planning and construction of public works are princi­ pally derived from (1) annual appropriations voted from general - 17 ­

revenues by the Philippine Congress and (2) receipts from the'

sale of bonds from a special public works bond issue of l billion

authorized by Congress in 1955, of which nearly 80% has been

appropriated to various public works projects. Approximately

t250 million of this fund has been allocated to irrigatimn system

improvements, and about X37 million for flood control projects.

Both the Irrigation and River Control Sections of BPW are

considered to be capably staffed with supervisory engineers and technicians.

The Division of Ports and Harbors is responsible for

construction and maintenance (including dredging) of ports and

harbors facilities, shore protection and aids to navigation.

It receives funds from a Portworks Special Fund derived from

wharfage fees in addition to sharing in other Bureau funds.

Imother independent government agency, the Irrigation Service

Unit, has the responsibility for installation of pumps required foi irrigation systems developed by groups or associations of farmers on a reimbursable basis.

Planning activities of the governmental agencies described have been directed to the particular water utilization function with which each is charged with the exception of the iingat and

Marikina Dams which have been planned as multi-purpose projects, and Ambuklao and Binga hydro-electric projects, which have other incidental benefits. The national administration and members of

Congress have shown an increasing interest in attaining maximum - 18 ­ utilization of the national water resources, and plans for immediate construction of Angat Dam and of flood control works on lower Pampanga River have been held up pending consideration of the effect on the latter of additional storage that would be obtainable by an increase in height of the dam to be built on ingat River. Interest in this possibility has recently extended to consideration of multi-purpose potentials of the other river basins heretofore mentioned.

Status of Planning

Review of the volume of basic data available and the current status of water utilization planning in the respective river basins indicates that they vary widely, with two or three watersheds offering an immediabe opportunity for consideration of a comprehensive water utilization and development program, whereas the remainder require additional time for the procure­ ment of basic data, analyses thereof and preparation of essential hydrologic design and economic studies. Details of the data available and of planning so far undertaken in the

Pampanga and Agno River Basins are well presented in a

"Preliminary Report on the !WTater Resources of Central Luzon" prepared by a committee representing all of the government4 agencies concerned with this subject. The status of planning in each of the seven river basins ccncerned is discussed as follows: - 19 - Pampanga River Basin:

This watnrshed of 3,912 sq. km. (3,0 sq. m.) and over 1,000,000 inhabitants has had the most thorough water development planning and treatment of the many watersheds and river systems in the Philippines for several reasons, including its extensive area of lands suitable for agri­ cultural development, its proximity to the metropolitan area of Manila and its abundant rainfall for six months or so of each year. The basin is saucer-shaped with a rather narrow fringe of hills and lot mountains around the north, east and a portion of the west sides, and at the south. The lower 150 km (93 mi) of the Pampanga River

System, and the lower 50 kms. (31 mi) of its principal tributaries, and Rio Chico, are subject to overflow by damaging floods, an area of 7,200 sq. kms.

(850 sq. mi) being affected. The south central part of the basin is occupied by depressions known as the Candaba and San Antonio Swamps, the low point of the former being at mean sea level, or about four meters below the lower rim of the Candaba Swamp area, nearly 35 km (12 mi) from the river's outlet into anila Bay. Both swamps have large natural storage capacities at flood stage, but nevertheless have been utilized extensively for development of rice pad­ dies and other agricultural (and even residential) purposes

The total mountainous part of the watershed is about 54% of the entire watershed, but is broken up into many small - 20 ­

independent tributary systems, the larger of which are the upper Pampanga River, the Angat River and the upper

Talavera River. The mountainous areas have been searched

far suitable dam and reservoir sites by N.P.C. and B.P.W.,

and such sites on the Angat have been fully surveyed and explored. Sites on the upper Pampanga (at Pantabangan)

and upper Talavera (at Lumboy) have been giver preliminary

study based on general topography, and two or three other sites have been proposed for preliminary study.

The proposed Angat Dam, though planned primarily for

power generation, will provide additional water for domestic

supply of hanila and Suburbs, and for irrigation of agri­ cultural lands downstream in the ,,ngatValley. It has also been studied as to flood control storage potentials, and is believed to offer an opportunity to obtain about

409,000,000 cubic meters (330,000 ,F)of additional reservoir capacity through a 17 meter raise in height of dam at an estimated cost of about 32,000,000. The estimated cost of the dam as originally proposed (usable capacity 660,000,000 cu. m. or 535,000 AF) without flood control storage is 157,500,000.

The proposed Pantabangan Dam on the upper Pampanga

River would have an estimated reservoir capacity of about

362,000,000 cu. m. (295,000 inF) if built to a height of - 21 ­

48.5 meters (160 ft.). Its drainage area is 860 sq. km. (551 sq. m.). A much larger capacity could be obtained

with greater heights of dam. Its power generation and

flood control capabilities have been studied superfi­

cially, but have not been carried farther because the

reservoir site is now devoted in large part to rice cultivation, for which there is at present a national shortage.

The proposed Lumboy Dam on the upper Talavera would provide a maximum reservoir capacity of 212,000,000 cu. m.

(172,000 AF) at a height of 91.5 m. (500 ft.) and would have a drainage ,-ea of about 263 sq. km. (109 sq. m.).

Its potentials have been studied to about the same extent as the Pantabangan project.

.hile all of these proposed projects would provide for power generation, with the possibility of added water supply, their regulating capabilities as to flood control are primarily applicable to the river channels immediately downstream, since the size of the drainage areas controlled is quite small in comparison to the total watershed con­ tributing to the Pampanga River System at point of entry into the San Antonio and Candaba Swamps.

A thorough review of these projects is needed to determine their importance as multi-purpose developments, before a comprehensive river development plan can be - 22 ­

adopted for the Pampanga Basin. Sufficient basic data

is available, and enough hydrologic studies and prelim­

inary plans are on hand, or close enough to completion,

to enable a team of experts to make such a review and

recommend a coordinated program for this basin. The

immediate need is for a determination as to whether or

not existing plans for construction of Angat Dam should

be revised to add flood control storage, so that its

construction will not be further delayed, and for

determination of the adequacy of existing plans for

alternative systems of outlet channels frcn lower Candaba

Swamp to Manila Bay, and recommendation as to which

alternative system should be developed. This consultant

will undertake these two tasks upon completion of this

report and plans to report his conclusions regarding them

before leaving the Philippines July 1, 1961.

It should be noted by any succeeding team of experts

that a number of' adverse natural conditions of river

discharge will be encountered in studying the multi-purpose

and overall develcpment of the Pampanga River systems

(and of other systems, too), such as the aggradation of river beds due to the sediment load carried, and the probability of salt water encroachment to be expected in the dredging and improvement of outlet channels below

Candaba Swamp. Ground water utilization has not as yet - 23 ­ reached a stage of overdraft, but it is probable that

such utilization will develop and that replenishment measures will eventually be needed.

Flood zoning, particularly in areas that are

regularly inundated to the hazard of inhabitants, will warrant consideration. The need for preparation,

adoption and enforcement of master plons for river im­

provements and water resources development is well

illustrated by the situation that has developed in the

Candaba and San Antonio Swamp areas of the Pampanga River Basin.

Squatters and others have been allowed to build their

homes in these natural depressions which have always baen

inundated by flood flows of the Pampanga River and Rio

Chico. In consequence, considerable property damage has

been occasioned during recent floods, and use of the

depressions for their natural functions as regulating

reservoirs has caused increasing complaint from the inhabitants. It is physically and economically impracti­ cable to eliminate or even substantially reduce the

natural flooding of these depressions, and they must be so utilized and reserved for this purpose insofar as encroachment of homes and buildings is concerned. When this is accomplished, it may have to be done at great expense to the government in the acquisition and clearance of buildings in the area which should never have been permitted to have been erected in these depressions. Similar forms of encroachment are - 24 ­

found in other flooded areas, and along river channels

where levees will have to be built in the future in each of the basins with which this report is concerned,

Enforcement of building restrictions designed to prevent

such encroachment, which should be a part of each basin t s master plan of water developments would not only greatly reduce the future cost of government acquisition of lands

and improvements for multi-purpose dam and reservoir sites, and for rights-of-way for river levees and other water utilization structures, but, if so applied as to prevent encroachment of buildings on areas subject to natural flooding, would in some cases eliminate the need for and expense of construction of any flood control improvements to protect such areas.

Agno River Basin

This river basin of 5,600 sq. kms. (2,200 sq. mi.) area is located in Central Luzon, adjoining Pampanga River

Basin on the west. The plains area of the basin is abutted by the large mountainous watershed of the Agno River on the north; by a low divide from the Pampanga watershed on the east, by the sizable watershed of Tarlac River on the south, and by the foothills of the Zambales Range and

Lingayen Gulf on the west. The Agno River, of 2,630 sq. kms. (1,000 sq. mi.) watershed area, and its principal tributary, Tarlac River, of 1,596 sq. kms. (605 sq, mi.) - 25 ­

area, discharge from the mountains and travel across the

plains from opposite sides to a confluence a short distance

downstream from Poponto Swamp, from which point the

combined flow travels about 45 kms. to .

The river divides into two main channels approximately

10 kms. from the Gulf and delivers its flood discharge

through separate channels across its delta to two mouths

located about 6 kms. apart. Poponto Swamp is a natural

reservoir which floods to a depth of two meters or more

during the rainy season from direct flow of Tarlac River

and overflow from Agno River, but dries up in the summer.

It is used for fish culture when flooded and for agrioul­ ture when dry.

Overflow of flood waters has occurred ovev the lower

140 kms. (87 mi.) of the Agno River channel and nearly 40 kms. (25 mi.) of the Tarlac River channel, the entire plains

area of the Agno River Basin having been subject to flood hazard during the most severe storm periods of the past with the exception of high ground at and west of Urdaneta.

The total area flooded in 1935 was estimated at 1,720 sq. kms. (665 sq. mi.).

The plains area is almost entirely devoted to agricultural pursuits, such as the growing of rice, corn, cane and tobacco, and to commercial fish culture. This area is quite thickly settled, with many towns and barrios,, - 26 ­

and at.present'has a population of some 780,000 inhab-.

itan s. The principal municipality is City' near

the coast, which has considerable commercials, and a small amount of light industrial development.

Plans have been prepared for a flood control system. of levees and channel cut-offs for the Agno River Basins

utilizing Poponto Swamp for peak regulations and a substantial portion of this system has been constructed.

Completion of this systems and repair of levees breached during floods of August 1960, should rate very highly as to need for immediate attent-i.on.

Two hydroelectric projects, the Ambuklao and Binga, which also provide some irrigation benefits, have been completed in the mountainous portion of the watershed, and 4 more sites are planned for .hydroelectric development but multipurpose developments have not as yet had much considerations and no currently proposed projects are being investigated as to such possibilities.

Several additional damsites are proposed for hydro­ electric development, and considerable basic data and some of the hydrologic studies necessary for consideration of nultipurpose use of these sites are available. It is anticipated that, within a reasonable period of time a onsulting team could, with the assistance of Philippine lovernment agencies, formulate a comprehensive plan of - 27 ­

water resources development for the Agho River Basin.

The problems of sedimentation, salinization and future

increase in use of ground water for domestic, industrial,

irrigation and other purposes will undoubtedly be en­ countered in the study of this basin.

A tour of the upper watershed of the Agno River

reveals that numerous large landslides and eroded areas

are in evidence and appear to be increasing in number and

extent. Some of these may be due to natural causes but

most are obviously caused by man-rnAde conditions. One of

the contributing factors is the practice of local residents

of burning off sizable areas of hillside or mountain-side

brush or tree cover in order that they may use the area

for planting bananas, rice, or for other agricultural

purposes. The more serious slides in the upper Agno watershed, however, are found along the Baguio-Ambuklao-

Binga roads, and are unquestionably attributable to lack

,of proper drainage, terracings wattling, etc., of road cuts and fills. The rock, sandy gravel and other debris eroded from these slide areas is and will continue to be washed into the channel of the Agno River and, to a considerable extent will be deposited in the reservoirs of Ambuklao and Binga Dams, thus reducing their periods of usefulness, or, if originating below these reservoirs, the debris and silt will deposit in the channel of Agno - 28 -

River andcause it to aggrade and overflow. The serious­

ness of this problem cannot be exaggerated, and steps must

be taken soon to control and prevent the man-made causes

of such hillside erosion if flood control and other types

of water utilization are to be effective in this river basin.

Cotabato River Basin - (Rio Grande de vindanao)

This basin, locr.ted in the southwest portion of the

island of Mindanao, has a watershed area of 19,700 sq. km.

(7,600 sq. m.). The principal tributary, the Pulangui

River, drains a mountainous watershed of 7,840 sq. km.

(3,oo sq. m.). The Dansalan- is another main tributa;'y but of much smaller watershed area and less mountainous character. is a natural feature affecting runoff from a limited portion of the watershed, and the Linguasan Marsh regulates overflow from Pulangui River during flood periods.

The Cotabato River basin, with a current population of approximately 880,000, is now rather sparsely settled, with concentrations around each of several municipalities in area. Agricultural, fish culture and logging pursuits constitute the principal activities of the basin, there being little industrial developmer.t as yet. The port of

Cotabato has served as an outlet for the entire basin, but is silting up to the point of near uselessness. - 29

Correction of this condition appears to be the most

immediate need of the basin, followed by flood protection

to the municipality of Cotabato.

Sizable hydro-electric developments have been proposed

in this watershed by N.P.C., including a large project on lower Pulangui River, but they have not been explored beyond preliminary examination as yet. No multi-purpose use of the contemplated dam and reservoir sites has as yet been proposed, and it appears that additional basic data and hydrologic studies would be needed to formulate a reasonable development program of this nature.

Most of the flood damages occasioned in the past have taken place in the lower reaches of the Pulangui and

Dansalan-AUlah Rivers and a short distance downstream from their confluence, which forms the Cotabato River, although tributaries are subject to overflow at a number of places.

A total length of nearly 260 km. (160 mi.) of river channel has at times overflowed. A preliminary program of flood control works utilizing Linguasan Marsh for flood regulation has been formulated but has not yet been financed.

The possibility of developing flood control storage as well as reservoir capacity for other purposes in connection with hydroelectric projects seems worthy of - 50 ­

exploration by a team of consultamts, but it is doubtful

if the basic data and hydrologic studies needed could be

made available within a reasonable period for them to remain on the job.

Compilation by such a team of an inventory of dams

and reservoirs sites deemed eligible for consideration of

multipurpose development located so as to serve flood

control as well as future irrigation water supply and

hydroelectric needs would be of great assistance, however,

in subsequent examination and exploration of potential

damsites and planning of their utilization by all govern­ mental agencies concerned.

Ilog-Hilabangan River Basin

This basin of 1,670 sq. km. (645 sq. m.) drainage

area is located in the southwestern part of the island of Negros, mostly in mountainous terrain. The Hilabangan

River is tributary to the Ilog River at a point about

15 kms. from its mouth at Panay Gulf, and most of the flood damage experienced is in this area.

The Ilog-Hilabangan River Basin is mostly mountainous

as to terrains with a flat flood plain of approximately

10,000 hectares (2,470 acres) located between the foothills

and the river mouth. The basin's population of about

90,000 is concentrated in this plain, which is primarily - 51 ­

devoted to agricultural use. An unusually severe flood

hazard threatens the plain from overflow along nearly 25 kms of the flog and 11 kms of the Hilabangan River

channels, due in part to the density of population and

also to lack of warning of floods, inherent in a relatively

small watershed of high discharge capability such as this.

Adequate flood protection appears to be the most immediate need for this basin.

Two or three damsites have been investigated by NPC within this basin bat satisfactory foundation conditions have not been found although investigation is continuing at one site on Ilog River. It had been expected that at least one of these would offer multipurpose possibilities.

A scheme has been prepared for a flood control program consisting mostly of channel improvements, below the confluence of the Ilog and Hilabangan Rivers. However, the above plans have been formulated with a minimum of basic data, and should be supplemented by more investiga­ tion before a comprehensive watershed development plan could be adequately defined.

Bicol River Basin

The Bicol River Basin is lccated in the southeasterly part of Luzon, and this river drains a watershed area of

2,850 sq. km. (1,100 sq. mi.), the lower portion of which - 32 ­

lies within the province of and the upper

part in the province of Albay. This watershed consists

of a long, flat valley floor bordered by low hills on

the west and by a series of volcanic peaks on the east,

the highest of vhich is Volcano of 2421 meters

(nearly 8,000 ft.) elevation at the upper end of the watershed. Lake Bato and Lake Baao are natural depres­

sions in the valley floor and serve to some degree as regulating reservoirs during flood periods. The water­ shed is rather heavily populated, having a total popu­ lation of 600,000, most of which is located in the valley areas with heaviest concentration around Naga City.

This City has some light industry, but the principal developments of the basin are agricultural. The basin appears to be in need of all types of water resources development, with flood control being one of the most essential, as almost all of the flat valley floor is subject to severe flooding and the area cannot be developed to its full potential until this hazard is overcome. Flooding of the lower reaches is primarily due to inadequate outlet capacity near the mouth of the

Bicol River, and the slow movement of flood water through this reach into San Miguel Bay. Flooding of upper reaches in Albay province is caused to a considerable extent by filling in of river channels with volcanic - 55 ­

debris washed down from the slopes of Mayon Volcano during typhoon type rainfall. No multi-purpose projects have as yet been proposed in this basin and the terrain is not favorable for such developments, except for possible utilization of the natural lakes.

The flood control scheme proposed for this basin is quite comprehensive but should he examined by a team of experts to confirm the necessity of leveeing the Bicol

River from Lake Bato to its outlet at San Miguel Bay, which would complicate lateral drainage by creating higher stages of flow during flood periods. Basin

The Agusan hive:, located in the northeast part of the island of Mindanao drains an area of 12,000 sq. km.

(4,640 sq. m.). The watershed is long, flat and fairly wide with ranges of mountains of moderate elevation on the sides and the upper or southerly end. The northerly end is bounded by the Mindanao Sea. Extensive marshes are found in the central part of the watershed. Flood damage has in the past occurred along 150 km. (95 mi.) of the Agusan River channel at several points. Studies have not as yet been undertaken of multi-purpcse or watershed development of this basin, but mountainous terrain in the upper portion and long swampy areas in the central - 54 ­

part seem to afford an opportunity for such developments.

The Agusan River basin has an estimated population of

but 175,000 the larger portion of which is concentrated in

the vicinity of City near the mouth of the river.

Access to central and upper areas of the basin has been hampered by lack of good roads. Settlement of these

underdeveloped areas is proceeding quite rapidly since

construction of a new through road was completed early in

1961. Logging is the principal activity of the region,

with agriculture expanding with opening of the new road.

Early preparation and enforcement of a master plan of

water resources development and flood control is vital if

settlement of the area is to be regulated to prevent

encroachment on areas subject to flooding and to thus avoid

interference with water development projects that will be

needed later as we3l as to minimize the need for flood

control improvements in the future.

Municipal water supply and flood protection for

Butuan City seem to be the most pressing water development requirements at this time.

Very little information relative rainfall and runoff characteristics of this basin has been accumulated.

Additional rainfall data and correlation will be required, and considerably more streamflow measurements - 35 ­ must be obtained, before realistic estimates can be prepared of normal or flood discharge. A team review of the basin topography, both from the map and the ground, would seem necessory to ascertain if potential damsites exist and if multipurpose use is foresecable. A period of investigation by Philippine Government agencies of any such sites that might be recommended could be under­ taken while additional rainfall and runoff date is gathered.

Cagayan River Basin

This, the largest river basin in the Philippines, covering an area of 26,430 sq. km. (10,200 sq. mi.), is located in the northern portion of Luzon. The Cagayan

River receives its flow from three principal sources ­ the upper Cogoyan River and the , the watersheds of which extend southwrd to the watershed of the Central

Luzon plain, and the Rio Chico, which drains a mountainous watershed on the west side of ; in addition, a number of smaller watersheds discharge directly into the Cagayan River at other locations. The upper portion of each of the larger watersheds is mountainous, the range on the west side being the highest in the Philippines.

The valley floors of the Cagayan, Nagat and Chico Rivers are in general quite rolling with occasional flat areas occurring adjacent to the river channels. - 36 ­

ithe population of the Cagayan Valley is estimated at

about 960,'00 inhabitants scattered throughout the Valley in many towns and barrios. The principal municipalities

are , a seaport at the mouth of the Cagayan River,

Tuguegarac, capital of Cagayan Province and Ilagans capital

of Province. The principal activity of the river

basin is agriculture, with logging in upper watersheds

and some . Development of the Cagayan Valley is

still in the early stages and it is expected to offer

unusual opportunities for expansion and intensification

of agricultural production and for industrial development over a period of time.

The Cagayan River Basin appears to offer interesting

prospects for every field of water utilization, there being

a current demand for additional irrigation systems and for

generation of hydro-electric power. There is a need for

development of adequate port facilities, the efforts in

this respect at Aparri having been fruitless due to

sedimentation and sand deposition at the mouth of Cagayan

River. Flood control improvements are needed on various

reaches of the Cagayan and its tributaries, bank erosion

being a frequent problem. Due to constriction of Cagayan

River Channel by converging hills and high ground some

55 kms. (25 mi.) above its mouths flood stages are raised - 57 ­

to 8 meters or more above low stages causing overflow of

banks of Cagayan River and Rio Chico, and of tributary

streams affected by backwaters for a distance of 60 km. (58 mi.) upstream from this construction.

Topography of the Cagayan, Magat qnd Chico River,

appears well adapted to development of reservoir storage

at locations favorable to flood control and power generation as well as other uses. but study of potential dainsites for such storage has only baen applied to hydroelectric

possibilities so far, the N.P.C. having three damsites

under investigation. Expansion of existing irrigation systems is also under consideration; and water supply is

a current municipal problem and will become an industrial

problem. Multi-purpose development of reservoir storage therefore appears to be both a need dud a possibility for further development of Cagayan Valley.

Very little basic data is available for the conduct

of investigations along this line, and obviously considerable

time will be required to develop and analyze such data.

The first need appears to be the inventorying of potential. dam and reservoir sites at serviceable locations, plus a recommended program for the gathering supporting data.

This would pave the way for the studies and investigations described hereafter that must be made prior to formulation - 58 ­

of a watershed development program. During this period,

it is likely that there will be a demand for flood control

work, particularly along the lower reaches of Cagayan River, which will have to be met on an expedient basis. Needed Planning:

If fullest utilization of its watersheds is to be achieved

by the Philippine Republic, a comprehensive study of the water

resources of each basin should be made by engineering agencies

of the Philippine Government, in order of urgency of need, as

rapidly as possible. Such a comprehensive study should include

a determination of the availability of water in each water basin,

i.e., the water crop, at strategic locations and at all times of the year for period of record and for average periods, and should take into consideration possible changes in watershed covers in climatic conditions and other characteristics which will affect such availability in future years. It should also include a determination of present and future requirements of the basin for utilization of the water resources available, with liberal allowance for increased per capita demand and expanded population and industrial usage.

With the availability of its water resources, including both airface and groundwater supplies, and the water utilization requirements of a basin thus determined for both current and future conditions, and an inventory of potential reservoir W 39 ­

storage sites on hand, the way should be cleared for each agency to conduct its planning for its particular form of water

usage without duplication of preliminary engineering by other agencies, and without jeopardizing the future of other forms of water utilization and development.

These studies are so vital to and closely integrated with the future development of the nation that the primary responsibility for their accomplishment seems undoubtedly to fall upon the Philip­ pine Government, particularly since it has competent engineering personnel available to supervise this work. Furthermore, the seven river basins herein considered are but a few of the many similar basins of the Philippines which will need similar study as time goes on. Outside assistance will be helpful in getting a program properly started, in providing guidance for the studies which should be made by Philippine Government agencies, and in recommending additional supporting data that should be obtained.

In addition, outside assistance can be helpful in formulating at once, with the cooperation of the Philippine Government agencies, comprehensive plans for watershed development for the two or three river basins for which supporting data is now available. Summarizing the above comments relative to the status of planning for watershed development in the several river basins, it is concluded that the existing agencies of the Philippine

Government have performed capably in the planning of their - 40 ­

respective water development programs; that they recognize

the need for more and better data as to rainfall and runoff

measurement, ground water levels, sedimentation and water

quality determinations, evaporation and other phenomena, and

have programmed and are obtaining some expansion of these

activities; that these agencies, if provided with staffs of

adequate size, would be able to conduct the investigations,

designs, field explorations, economic analyses and other studies

involved in planning watershed developments.

It is also concluded that they would be benefited by-,outside

guidance in the selection and designation of dam and reservoir sites which are suitably located and physically adapted to multi-purpose utilization, as none of the existing agencies is charged with this

overall responsibility; that a recommendation by outside experts as to a program of additional rainfall and streamflow recording

stations, surveys, mapping and other basic requirements needed to support this investigation would enhance its prospects as to activation; and that a review and recommendation by outside experts of watershed developments now planned and awaiting financing and construction would be of great value in clearing away present uncertainties as to whether these projects conform to the best overall plan for development of water resources in the basin. Recommended Program for ICA Team

It is therefore recommended that the proposed ICA program -41­ for assignment of a team of experts to investigate and recommend multipurpose water development projects deemed desirable in the river basins heretofore described be modified to provide for the following tasks:

1. To review studies, reports, hydrologic data, plans

and other information available in various agencies of

thePhilippine Government pertaining to flood controls

hydroelectric, water supply, irrigation and other

water resources development projects.

2. Through field inspection and examination of aerial

photos, topographic maps, geologic maps, etc., to

ascertain and prepare an inventory of all dam and

reservoir sites within these basins deemed suitable

for investigation by agencies of the Philippine

Government for multipurpose development, current or .future.

5. To prepare and recommend a list of the principles and

procedures that should be applied by Philippine Govern­

ment agencies in considering multipurpose development

of the inventoried sites, including determination,

under future conditions as well as present, of the

water available for development and of the future

needs for the respective types of water utilization

and development, the amount of reservoir storage - 42 ­

required for these purposes, the extent to which

exploration of site and preliminary design of

contemplated multipurpose dams should be carried,

applicable methods for allocation of reservoir storage

to different uses and determination of costs chargeable

to such allocation, guides for determination of priority

of use and other factors necessary to assure adequate

investigation and planning of each project when the opportunity for such planning arises.

4. To review current plans for, and to recommend a program

of, mapping surveys (both aerial and field), installation

of hydrographic equipment, groundwater measurements, and

hydrologic studies considered necessary to support the multipurpose investigation in the prescribed river

basins, and to suggest possible schemes of development.

5. To review existing plans of the various governmental

agencies for hydroelectric power generation, flood

control, water supply and irrigation in the Pampanga

and Agno River Basins (and possibly the Cotabato River

Basin) and to recommend a comprehensive plan of water

resources development in each designed to serve the

best interests of the people of these basins, con­

sidering both immediate construction needs as well as

future requirements. Such a plan should include - 45 ­

provisions for replenishment of ground water storage

if and when overdraft conditions develop; protection

of water quality, particularly from known occurrences

of salt water intrusion; measures to cope with or

provide for troublesome sedimentation, and possibly

to provide for debris control in upper reaches of

these rivers. In addition to consideration of maximum

utilization of the water resources for the primary

purposes stated above, attention should be given to

'ther uses including navigation in the lower reaches,

fish and wildlife propagation, potential recreational

opportunities, and to possible reduction of flood losses

and future expenditures for flood control improvements

by application of flood zoning measures. 6. *Upon concluding the above assignments, to recommend

such continuing liaison with Philippine Government agencies

as deemed appropriate and necessary to carry out the

planning program herein presented.

The team of experts selected for the assignment should include members well qualified in the fields of (1) hydroelectric power generation planning, construction and operation, (2) water supply (both domestic and industrial) and irrigation, including preservation of water quality, (3) flood control planning, design and construction, (4) selection of sites and design of high dams of all types and (5) geology as applied to damsite - 44 ­

investigation and explorati6n, and preferably, ground-water

geology as well. Consultants expert in two or more of the above

fields would of course serve to reduce the number of team members

required. It is obviously difficult to estimate closely the time

or funds requirements for this team assignment, but it seems that

a period of nine to twelve months should be ample to complete

items 1-5 inclusive of the above programs and the present estimate of 4.1400,000 should be adequate.

It is anticipated that in order to expedite some of its work the team of experts might find it desirable to request that aerial mapping, hydrographic or survey equipment or other commodities or items originally programmed as counterpart contributions by the

Philippine Government be undertaken as contract operations at ICA expense, but should this develop V. additional cost to ICA should be offset by reduction in time originally estimated as required for the team study.

Qualifying features

It is certain that a team of experts must give technical attention to the problems induced by erosion attributable to landslides, bank-cutting and stream bed degradation, including those involving upstream debris deposits and also those involving acdimentation or silt deposits further downstream. Adoption of the most advanced methods of road design in mountainous areas is needed to correct serious erosion already occurring along - 45 ­

existing roads and prevent the same from spreading further as

new roads are constructed. This must be assured by full acceptance

and practice of correct road design by all agencies undertaking

road construction, even though the road is but incidental to other

primary functions, such as construction of an access road to a

damsite. Experience elsewhere has indicated that sound legislation,

sufficient to control the man-made activities which endanger

erosion, must be enacted and strongly enforced if a national program of water resources development is to prove successful,

since the deposit of debris and sediment in reservoirs and

river channels is detrimental and often ruinous to all forms of water utilization and development.

Mention has also been made of the ill-advised encroachment

by squatters and others on natural depressions, river-banks and

beds, and other lands essential to the passage of flood waters and other water uses in the river basin that will be necessary in the future. The watershed development plans that would be formulated under the program presented herein would provide basic information as to the areas that shorld be protected from encroachment, but their usefulness would be stultified unless effective legislative and enforcement measures are devised by the Philippine Government to prevent such occurrences.

The preceding portion of this report has been concerned with the technical phases of the contemplated multipurpose investigation. It should be noted that if it is to be useful - 46 ­

and effective, considerable effort and expense on the part of

the Philippie Goverment will be involved. This support has

been committed but may involve a larger contribution of funds,

manpower and commodities than heretofore apparent. Furthermore,

this investigation should be followed by construction of needed

projects as soon as plans are finalized if the maximum benefit

is to be gained from this program. At the present time the

supply of funds for public works projects follow the rather

uncertain allocations of the annual public works appropriations

bills approved by the Philippine Government and the occasional

sale of public works bonds which is not always productive. A

positive and regular appropriation of funda by the Philippine

Government sufficient to assure that its governmental agencies

will be able to promptly perform the correlative engineering

functions of the proposed multipurpose investigation appears

necessary to justify the IGA participation recommended, and

for effective utilization of the engineering investigation to

be jointly performed, provision should also be made for a regular

and adequate appropriation of planning and construction funds.

HEHedger/vpp -C4

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