Timeline: Water spilling operations of Luzon dams

Posted at 10/16/2009 4:54 PM | Updated as of 10/25/2009 1:30 AM

October 6

 

6:00 am

The Pantabangan dam starts releasing water at 250 cubic meters per second (cms)

3:45 pm

The Pagasa issues a flood warning to NPC.

4:30 pm

The reservoir water level (RWL) of the San Roque dam is at 285.5 meters above sea level.

 

The NPC announces that spilling operations will be done at 12:03 am of October 7, 2009

 

The NPC faxes a warning to the SRPC. SRPC confirms that they received the warning but says that they are not responsible for disseminating the information to the people.

October 7

 

12:03 am

The San Roque dam’s RWL jumped to 286.5 m in a matter of hours.

 

The San Roque dam releases 181.5 cubic meters per second (cms) with 1 gate with a total opening of 1 meter.

12:06 am

The NPC issues its final warning telling people to evacuate to higher ground as more water is expected to be released from the dam.

10:00 am

The Pantabangan dam continues to spill 250 cms, with 1 gate open with a total gate opening of 3.2 m.

 

Meanwhile, the Angat dam’s RWL is 213.68 m—lower than the previous day’s RWL of 213.84 m.

 

The Magat dam’s RWL increases to 191.94 m from 191.35 m the previous day due to the additional inflow from the upstream of the Magat dam watershed.

Before 11:00 am

The increase of water inflow from the Ambuklao and Binga dams in Benguet totaling 850 cms, with the amount of rainfall from typhoon Pepeng, the San Roque dam’s RWL increased to 287.15 m.

11:00 am

The San Roque dam opened 3 gates, each with an opening of 1 meter.

October 8

 

Before 11:00 am

Water level in the San Roque dam reached 288.5 m.

11:00 am

All 6 gates of the San Roque dam were opened totaling 17 meters of gate opening.

 

There is a 2,700 cms inflow to and an outflow of 3,600 of water from the San Roque dam.

2:00 pm

The Pantabangan dam in Nueva Ecija RWL is 220.28 m with an inflow of 1,705 cms with 2 gates opened totaling 4 meters of opening.

 

The Pantabangan dam records an outflow of 250 cms to 500 cms.

4:00 pm

The Magat dam’s RWL increases to 192.31 m from 192.22 m the date before. Its 4 gates are opened at 7 meters allowing an outflow of 1,578 cms from 2,245 the previous day.

 

In Benguet, the Ambuklao and Binga dams combined outflow is 2,341 cms. The water the dams release goes to the San Roque dam.

 

The San Roque dam’s outflow is 3,156 cms with 6 gates open and its total opening of 15 meters.

Pagasa’s flood advisory as of 4:00 pm

Pagasa’s press release says that the municipalities that are likely to be affected in Pangasinan are: San Manuel, San Nicolas, Tayug, Sta. Maria, Asingan, Villasis, Alcala, Bautista, Rosales and Bayambang and are advised to evacuate to higher grounds immediately due to expected widespread flooding. The target area of Magat dam includes the municipalities of Ramon, San Mateo, Aurora, Cabatuan, Luna, Reina Mercedes, Burgos, Naguilian and Gamu in the province of Isabela. All municipalities/cities in the target area of Pantabangan dam particularly in Rizal, Bongabon, Gen. Natividad, Palayan City, Cabanatuan City, and Sta. Rosa are advised to seek higher grounds. All residents along the Agno river, Magat river and middle Cagayan river and upper Pampanga river are advised to evacuate and stay tuned to warnings/advisories from Pagasa. The Pagasa will continue to provide update on the monitored reservoirs until such time that all spillway operations are terminated.

October 9

 

2:00 am

The RWL in the San Roque dam was 289 m, only a meter lower than its spilling level.

 

All 6 gates of the San Roque dam are opened with a total opening of 27 m, allowing an outflow of 5,353 cms of water into the Agno River basin.

 

The increase of outflow from the San Roque dam is due to the increase of inflow from the Ambuklao and Binga dams. Both dams released 3,452 cms of water.

5:00 am

The Pantabangan dam’s outflow is 600 cms. Its RWL is at 220.61 m with an inflow of 747 cms. Its 2 gates are opened with a total of 9.4 m.

6:15 am

The RWL of the Magat dam increases to 192.55 m from 192.22 the previous day. Its 6 gates are open with a total gate opening of 14 m. The dam increases its outflow to 3,400 cms from 1,578 cms.

 

The Angat dam’s RWL is 213.93 m. It is forecast to open its spillway if significant inflow occurs.

Pagasa’s flood advisory and forecast as of 6:15 am

Pagasa warns that residents of all municipalities/cities in the target area of Pantabangan dam particularly in Rizal, Bongabon, Gen. Natividad, Palayan City, Cabanatuan City, and Sta. Rosa must seek higher grounds. The target area of Magat dam includes the municipalities of Ramon, San Mateo, Aurora, Cabatuan, Luna, Reina Mercedes, Burgos, Naguilian and Gamu in the province of Isabela. All residents along the Agno river, Magat river and middle Cagayan river and upper Pampanga river are advised to evacuate and stay tuned to warnings/advisories from PAGASA. The PAGASA will continue to provide update on the monitored reservoirs until such time that all spillway operations are terminated. The target areas of Angat/Ipo Dams are the municipalities of Bulacan namely: Norzagaray, Angat, San Rafael, Bustos, Baliuag, Pulilan, Plaridal and Hagonoy. The spillways of both dams are closed.

Widespread flooding occurred in the target municipalities of Pangasinan namely: San Manuel, San Nicolas, Tayug, Sta. Maria, Asingan, Villasis, Alcala, Bautista, Rosales and Bayambang.

The advisory says flood levels remained high within the next 24 hours.

1:00 pm

Total meter-opening of the gates of the San Roque dam is reduced to 7 m. The outflow decreases to 1,671 cms with an inflow of the same rate.

 

The dam’s RWL increase to 289.1, because the water was not yet able to adjust to the abrupt decrease of meter-opening in its gates.

 Source: the Pagasa Flood Forecast Branch and the National Power Corporation