Reservoir Management in Response Reservoir Management in Response to Floods and Water Shortagesto Floods and Water Shortages

International Training Program on Typhoon and Flood Disaster ReductionTaipei City, Taiwan, May 7-11, 2007

PACITA F. BARBANational Water Resources Board (NWRB)

Philippines

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Angat Dam

An average of 20 typhoons a year, directly hit the Philippine Area of Responsibility

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ANGAT DAM

• Located in Luzon Island

• Basin area – 568 km2

Basin Rainfall:• ave. annual – 2,449 mm• max. – 4,919 mm in 1972• min. – 1,430 mm in 1982

Ave. annual inflow - 1872 mcm

ANGAT MULTIPURPOSE DAMANGAT MULTIPURPOSE DAM

ANGAT DAM

• Located in Luzon Island

• basin area – 568 km2

Basin Annual Rainfall:• ave – 2,449 mm• max – 4,919 mm in 1972• min – 1,430 mm in 1982

Ave. annual inflow– 1,872 mcm

ANGAT MULTIPURPOSE DAMANGAT MULTIPURPOSE DAM

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P U R P O S EP U R P O S E

Supplies the 97 % water needs of Metro Manila

Irrigates the farmlands of Bulacan and Pampanga of about 27,000 has.

Generates power with output capacity of 246 MW contributing to Luzon Power Grid

Flood control for downstream of the dam with flood storage capacity of 63 mcm.

ANGAT MULTI-PURPOSE DAMThe AngatDam was constructed in 1967

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FEATURES OF ANGAT DAMFEATURES OF ANGAT DAM

RESERVOIR

Usable Storage : 850 MCMDesign Flood Water Level : El. 219 m.Normal High Water Level : El. 212 m

DAM

Date of Operation : October 16, 1967Dam Type : Storage, Earth and Rock FillDam Height : 131 m.Crest Elevation : El. 223.50 m.

SPILLWAYSpill Elevation : El. 202 m.No. of Gates : 3 ( 12.5 m, x 15 m.)Elev. of Top Gates : El. 217 m.Design Flood : 5,800 m3/sec

MAIN POWERHOUSE

Turbine : 4 unitsGenerator : 4 units

Capacity : 55,555 KVAPower Factor : 0.90

Installed Capacity : 200,000 Kw

AUXILIARY POWERHOUSETurbine : 6 unitsGenerator : 4 units

Capacity : 55,555 KVAPower Factor : 0.90

Installed Capacity : 46,000 KwFOR ITW

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Conservation Curves:

- Upper Rule Curve : Elev. 212m - Elev. 185m

- Lower Rule Curve : Elev. 207.3m – Elev. 180m

Max. Res. Supply Curve (spilling level):

- Elev. 212m for non-flood season - Elev. 210m for flood season

EXISTING ANGAT RESERVOIR OPERATION RULE CURVES

175

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OPERATION RULE CURVESOPERATION RULE CURVES

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OPERATING GUIDELINESOPERATING GUIDELINES

1. The water level of the reservoir at any given time should not be allowed to go below the lower rule curve except during critical water shortages where it should first be cleared with the NWRB.

2. During flood season and critically wet, which the forecastedinflow will be more than the design inflow, additional water allocation is allowed to mitigate spill that causes possible damages downstream. The amount of water allocated is monitored so as to prevent indiscriminate releases that will affect the normal requirements for water use in normal operation.

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MANAGEMENT OF ANGAT RESERVOIRMANAGEMENT OF ANGAT RESERVOIR

1. High level management

2. Low level management and change in demand

3. Normal management

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AGENCIES DIRECTLY INVOLVEDAGENCIES DIRECTLY INVOLVED1. National Power Corporation (NPC) – dam owner who operate and

manage the dam and responsible for the flood operations

2. Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) – issues flood bulletins and flood information

MONITORING AGENCIESMONITORING AGENCIES1. Department of Public Works and Highways (DPWH)

2. Office of Civil Defense (OCD)

3. National Water Resources Board

HIGH WATER LEVEL MANAGEMENTHIGH WATER LEVEL MANAGEMENT

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Spot inspection of outlet, etc.

Weather forecast/ hydrological dataInflow forecast

Patrol of downstream and

alarm

Notifying related agencies

Start discharge

End

Flood control

Notifying related agencies

High level managementHigh level management……

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High level managementHigh level management……

DOWNSTREAM WARNINGi) Dam discharges warning must be executed to the downstream

communities through the siren installed in the warning stations or through the loudspeakers installed in the warning vehicles for areas not covered with the warning stations;

ii) The warning message shall be announced alternately in English and local dialects; and

iii) The warning should be issued at least 4 hours before the commencement of the pre-releasesFOR IT

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High level managementHigh level management……

PRINCIPLE OF DAM DISCHARGES

i) Increasing rate of dam discharges shall be within the allowable rate of 52.8 m3 within 30 minutes;

ii) No over discharges from the dam. The total outflow from the turbines and spillway should be less than or equal to the reservoir inflow; and

iii) Maximum use of water or the capability of the plant is required; FOR IT

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AGENCIES INVOLVED:1. National Water Resources Board (NWRB) - regulatory body.

2. National Power Corporation (NPC) - owner , operator and water user for power generation

3. National Irrigation Administration (NIA) – water user for irrigation

4. Metropolitan Waterworks and Sewerage System (MWSS)-water user for water supply

5. Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) – issues advisory on climate/weather forecasts

LOW WATER LEVEL AND CHANGE IN DEMANDLOW WATER LEVEL AND CHANGE IN DEMAND

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NIA-AMRIS Requirement

Climate Forecast by PAGASA

Status of Angat Dam & Reservoir by NPC

MWSS Requirement

Reservoir Yield Optimization by NWRB

Technical Working Group

Top Level Group

NWRB Board

Inflow

Seasonal Forecast Inflow

Reservoir Water Demand

Reservoir Releases for MWSS and NIA

Low level, normal level and Low level, normal level and change in demand managementchange in demand management……

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WATER ALLOCATION/WATER RELEASES

Reservoir yield is determined by simulation using water balance analysis

Inflow design is based on the percentages of historical mean of inflow, depending on climate forecast

In case of water shortage, the municipal use is the priority over irrigation use and power generation

All releases are subject for NWRB Board’s approval

Low level, normal level and Low level, normal level and change in demand managementchange in demand management……

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Facility management is realized so that Facility management is realized so that AngatAngat dam facilities continue dam facilities continue functioning properly.functioning properly.

•• conduct of regular and spot inspection,conduct of regular and spot inspection,•• Improvement, and Improvement, and •• measurements for leakage, uplift and deformation.measurements for leakage, uplift and deformation.

For preservation of For preservation of AngatAngat reservoirreservoir

•• survey and observation are carried out for landslide, sediments,survey and observation are carried out for landslide, sediments,water quality and environmental preservationwater quality and environmental preservation

NORMAL MANAGEMENTNORMAL MANAGEMENT

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Seasonal variations of rainfall and the impact of extreme climate events

Lack of equipment, instrument and tools for inflow forecasting

Small storage capacity of the reservoir

The reservoir is managed by different agencies in water sector with different agency’s policies and plans

CHALLENGES IN THE RESERVOIR MANAGEMENTCHALLENGES IN THE RESERVOIR MANAGEMENT

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Inflow vs. Water RequirementInflow vs. Water Requirement

Total Inflow = 577.00 Total Requirement = 1,045.71 Shortage = 468.70

January - June(unit: mcm)

Total Inflow = 1,682.27 Total Requirement = 1,083.72 Stored Water = 598.55

(unit: mcm)July - December

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Challenges…

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Average Monthly Inflow of Angat Dam

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El NinoLa NinaNormal

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Historical Annual Inflow

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TOWARDS EFFECTIVE MANAGEMENTTOWARDS EFFECTIVE MANAGEMENT

Formulation of an effective operation policies and strategies including the revision of the Angatoperation rule curves;

Improvement of climate forecast for disaster mitigation anddevelopment of tools to improve water allocation decision; and

Strengthening of flood forecasting and warning system for dam operations. FOR IT

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NATIONAL WATER RESOURCES BOARD8th Floor, NIA Building, EDSA, Quezon City

Telefax No. (632) 9202641 / 9202654Website: www.nwrb.gov.phFOR IT

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