La Mesa Dam in Quezon City is placed on red alert status due to possible overflow, while Angat Dam in Bulacan is on "preparatory phase" on Wednesday, in anticipation of the arrival of typhoon "Ulysses."
According to Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) hydrologist Richard Orendain, La Mesa Dam's water level was at 79.37 meters as of Wednesday morning.
With the projected rainfall of 160 millimeters within the watershed, it could easliy reach La Mesa Dam's spilling level of 80.15 meters.
Areas that may be affected with its possible overflow are Fairview, Forest Hill, Quirino Highway, Capri, Goodwill Homes, Santa Quiteria and San Bartolome in Quezon City; Ligon, North Expressway, and Huerta in Valenzuela City; and Malabon.
Also on Wednesday, Orendain said PAGASA has issued a preparatory phase for flood warning in Angat Dam in case the reservoir needs to release water.
Angat Dam's current water level was 205.50 meters, almost 5 meters short of its 210-meter normal high water level.
Orendain said the projected rainfall within the watershed is 220 millimeters, which could push the water level of Angat Dam to 211.96 meters.
"Nag-issue na kami ng preparatory phase sa Angat Dam. Kung lalagpasan pa ang projected rainfall na 220 millimeters within the Angat watershed, posible magpakawala ng tubig. (We have already issued a preparatory phase at Angat Dam. If it exceeds the projected rainfall of 220 millimeters within the Angat watershed, Angat Dam could possibly release water from its reservoir)," he said.
Magat Dam in Isabela is also being closely monitored as it could easliy reach the 193-meter normal high water level with the projected 160-millimeter rainfall over the watershed area.
As of Wednesday, Magat Dam's water level is at 190.14 meters.
"Sobra sobra ang papatak na ulan sa watershed ng Magat Dam sa forecast. Posible magdagdag ng bukas na gates na delikado na kapag nagrelease pa ng additional na tubig dahil may reported na na pagbaha sa Isabela and Cagayan particularly sa Delfin Albano na galing sa mga pag-ulan.
(Magat Dam could receive a lot of rainfall within its watershed based on the forecast. It is possible to open additional spillway gates which could already be dangerous when additional water is released. There is already a reported flooding in Isabela and Cagayan particularly in Delfin Albano due to recent rains)," Orendain said.
Two gates each with a 4-meter opening are currently releasing water from the Magat Dam reservoir.
Orendain said Caliraya Dam in Lumban, Laguna is also conducting water drawdown. Its current water level is 287.74 meters, while its spilling level is 288 meters. It is projected to receive 190 millimeters of rainfall during the passage of the typhoon.
Meanwhile, San Roque Dam in Pangasinan and Pantabangan Dam in Nueva Ecija may also receive significant rainfall within their watersheds but are still far from reaching their normal high water levels.
Flood bulletins and advisories have also been issued in Cagayan, Bicol, Pampanga, and Agno river basins, recommending the public and local disaster risk reduction management councils concerned to take appropriate actions.
Orendain said flood advisories have been also issued in Regions 1, 2, 3, 4A, 4B, 5, 8, and Cordillera Administrative Region due to the large circulation of the typhoon that may affect almost the whole of Luzon and parts of Visayas.