Recognizing the need for operational flood forecasting and warning system to help mitigate losses of life and property brought about by annual occurrences of flooding, the Government piloted a Flood Forecasting and Warning System (FFWS) for the Pampanga River Basin in 1973. The project was established with the financial assistance from the Government of Japan, the warning system proved effective than it led to the establishment of a similar system covering Agno, Bicol and Cagayan River Basins.
In April 1983, the Flood Forecasting and Warning System for Dam Operation (FFWSDO) project was conceived. The project was meant to prevent the occurrence of similar incident (i.e. Angat Dam) which result to the imprecedented flood heights that caused destruction and deaths downstream of the dam.
Implementation of the project was done stages (Phases I and II). Phase I, for Angat and Pantabangan Dams. Was completed in July 1986, was funded under the 10th Yen Loan Package from Japan Overseas Economic Cooperation Fund (OECF).
For Phase II, implementation was started last January 1990 and was fully completed by the on set of the rainy season in 1992. The major components of Phase II are the establishment of the PAGASA Data Information Center, flood forecasting and warning systems, flood forecasting and warning system at dam offices, hydrological stations, warning posts, repeater stations and monitoring stations.
The project was implemented with the National Power Corporation (NPC) and the National Irrigation Administration (NIA) as cooperating agencies and the Philippine, Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) as the lead agency.
The Flood Forecasting and Warning system for Dam Operation (FFWSDO) aims at the establishment of telemetered flood forecasting warning system that will provide the necessary information for the safe and cost effective operation of the existing five major dams in Luzon and to forewarn the people in the flood plains downstream of these damsites of the impending release of impounded water through spillways during typhoons. Phase I, involves the establishment of a FFWS covering Angat and Pantabangan watershed areas, while Phase II, involves the establishment of a FFWS covering Magat and Binga/Ambuklao watershed areas.
The Agencies directly involved in the implementation of the project such as NPC and NIA are dam authorities who operate and manage the Angat and Binga/Ambuklao Dams and Pantabangan and Magat Dams respectively amd the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) through its Flood Forecasting Branch which operates the flood forecasting warning systems. Monitoring agencies are the Department of Public Works and Highways (DPWH), Office of Civil Defense (OCD) and the National Water Resource Board (NWRB).
The complete FFWSDO has the following basic system and components:
Real-time telemetering system consisting of the optimum number of rainfall and water level gauging stations
Real-time processing computer system to forecast flood water inflow to the reservoir based on the telemetered rainfall data;
Flood warning system with warning disseminationfacilities and supervisory control stations in dam offices;
Overall supervisory system for the operation of the above system in the respective Central Offices of NPC, NIA, and PAGASA;
Monitoring system which will allow exchange of necessary information among the participating agencies in flood control and other related activities; and
Telecommunication system which provide the means for continuous information flow for the operation of the above system.
The project will result in the effective use of the hydrological data and information for the efficient operations and management of reservoirs and ensure the optimum use of the impounded water for power generation, irrigation, flood control and domestic water supply, the mitigation of flood damages, particularly loss of human lives, by timely and adequate warnings of impending release of impounded water through the spillways.
The Flood Forecasting and Warning System for Dam Operation consists of a network of telemetered gauging stations, warning stations, supervisory control offices of damsites linked with supervisory centers in Central Offices of NPC, NIA and PAGASA. The project’s major facilities are as follows;
|a.||Center at PAGASA||1|
|b.||Center at NPC and NIA||2|
|c.||Rainfall gauging station||19|
|d.||Waterlevel gauging station||7|
|e.||Fixed warning station||69|
|f.||Mobile warning station||24|
The Flood forecasting and Warning System for Dam Operation is composed of the following four major sub-system, namely;
|NAME OF DAM||AREAS COVERED|
|A. ANGAT DAM||NORZAGARAY TO PLARIDEL|
|B. PANTABANGAN DAM||RIZAL TO CABANATUAN CITY|
|A. MAGAT DAM||MARIS DAM TO NAGUILIAN|
|B. BINGA/AMBUKLAO DAM||SAN ROQUE TO CARMEN|
Each of the sub-system are composed of the following components:
The telemetering system is composed of rain and water level gauge stations (installed in selected places in dam watersheds) and radio telecommunication system for transmission of data.
In each damsite, at least three raingauge stations are installed in selected locations considered appropriate based on hydrological considerations, radiowave propagation and construction and maintenance accessibility.
The supervisory and control station (FFWS Dam Office) for the sub-system is located in each dam office. It supervises and controls the telemetering system and serves as the supervising control station for the warning systems within its area of coverage. It also performs the following functions:
Disseminates dam discharge warning;
Disseminates flood warnings issued by PAGASA;
Monitors the operating condition of the warning stations;
Prints out the collected data for compilation and utilization in subsequent analysis;
Analyses the collected data to forecast the water inflows in the reservoirs and implements the recommended reservoir operation program.
The FFWS Dam Office and rainfall/waterlevel gauging stations are linked by radio telecom network.
The FFWSDO’s integrated and warning system includes the following:
Fixed point warning stations categorized as Type-A and Type-B
Mobile warning stations (vehicles) equipped with loud-speakers and portable radio telephones.
A Type-A warning station is equipped with a speaker and radio telephone. Generally, it is installed in the most densely populated area of each municipality with the area covered by each each FFWSDO. The Type-B warning station is equipped with speaker only and is installed in barangays located between the coverage of Type-A stations.
In area not reach by both fixed point warning stations, a warning vehicle equipped with a speaker and radio telephone is provided.
Discharge/Flood warning notices are transmitted from the Dam Offices to the municipal halls which serves as the center for the dissemination of warnings. All flood warning operation are undertaken in close coordination with the FFWS Dam Offices, PAGASA and other government agencies.
Flood forecasting and warning operation includes a number of interrelated activities, each of which forms the following integral part of the operation:
Collection of hydrometeorological data on real-time basis.
Assessment of weather conditions affecting or expected to affect the reservoir catchment areas;
Streamflow simulation and flood forecasting;
Preparation and issuance of DICHARGE WARNINGS or FLOOD BULLETINS and FLOOD INFORMATION as the case may be; and
Dissemination of discharge warnings of flood warnings /information to the local, municipal, and provincial government offices, disaster coordinating councils and the general public through the FFWS Center, FFWS Dam Offices, OCD, DPWH, NWRB and other government agencies as well as the print and broadcast media.
The Warning/Information on flood are divided into two n(2) groups, namely; Flood Bulletin and Flood Information.
Flood Bulletin is categorized into four (4) kinds of warning namely: Flood Outlook, Flood Advisory, Flood Warning and Critical Flood Warning. The PAGASA prepares and issues the corresponding Flood Bulletins at the exact time.
In the issuance of Flood Bulletins PAGASA uses three (3) assessment levels as guides, namely:
ALERT W.L. - corresponds to such river discharge which will not cause flooding in the flood warning zone.
ALARM W.L. - corresponds to such river discharge which will not cause substantial flooding in the cultivated land and residential areas.
CRITICAL W.L. - corresponds to such river discharge that causes extensive flooding in cultivated land and residential areas.
Flood Information consists of two (2) types, namely: the Flood Warning Information and Flood Disaster Information.
The Flood Warning Information which is issued by PAGASA is the supplemental and periodical information on Flood Warning to the inhabitants in the flood warning zone.
The Flood Disaster Information is prepared and issued by the Office of Civil Defense (OCD) when a serious disaster due to flood is taking place in the flood warning zone.
The Flood Bulletins, Flood Warning Information and Flood Disaster Information will be disseminated to the government agencies concerned.
Dissemination of all bulletins and information related to flooding in the flood warning zones shall be the joint responsibility of PAGASA and concerned Dam Offices who are equipped with supervisory control of different warning facilities.