MANILA, Philippines — The recent rains brought some relief to several major Philippine reservoirs, but the latest PAGASA monitoring shows that the upward trend is losing momentum as the southwest monsoon, or Habagat, weakens.
Only four of the nine major dams monitored by the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) recorded increases in water levels over the past 24 hours as of 8 a.m. Friday, August 21.
The reservoirs that gained water were Angat, San Roque, Pantabangan and Magat dams, while water levels at Ipo, La Mesa, Ambuklao, Binga and Caliraya dams declined.
Angat continues to gain, but the bigger picture remains mixed
Angat Dam in Bulacan posted the largest increase among the nine monitored reservoirs based on the latest PAGASA figures, rising from 188.75 meters to 189.00 meters.
That translates to an increase of about 0.25 meter over the monitoring period.
The improvement is notable because Angat has been closely watched throughout the year after its water level plunged to critically low territory during the dry months. In July, government officials warned the public to conserve water after Angat reached its lowest level since 2010.
The reservoir has since recovered substantially following episodes of rain, including rainfall associated with the southwest monsoon.
Earlier this month, PAGASA data showed Angat rising sharply as rain replenished the watershed. On August 19, PAGASA recorded Angat at 186.41 meters, up 1.55 meters from the previous day’s 184.86 meters.
San Roque, Pantabangan and Magat also rise
Three other reservoirs posted modest gains.
San Roque Dam in Pangasinan climbed from 274.80 meters to 275.44 meters, an increase of 0.64 meter.
Pantabangan Dam in Nueva Ecija increased from 188.94 meters to 189.46 meters, gaining 0.52 meter.
Meanwhile, Magat Dam in Isabela edged up from 178.73 meters to 178.96 meters, a 0.23-meter increase.
The increases come after a period of significant improvement in several Luzon reservoirs as persistent Habagat rains replenished watersheds.
For comparison, PAGASA’s August 19 monitoring showed increases in seven of the nine monitored dams, including Angat, Ipo, La Mesa, Binga, San Roque, Pantabangan and Magat.
Five dams record declines
The latest figures, however, show that the rain-fed recovery is uneven.
Ambuklao Dam in Benguet dropped from 751.72 meters to 751.23 meters, a decline of 0.49 meter.
Caliraya Dam in Laguna fell by 0.32 meter, from 286.72 meters to 286.40 meters.
La Mesa Dam in Quezon City decreased from 79.86 meters to 79.59 meters, while Binga Dam in Benguet slipped from 574.42 meters to 574.31 meters.
Ipo Dam in Bulacan also declined slightly, from 101.00 meters to 100.93 meters.
PAGASA’s monitoring data also show that reservoir conditions can change rapidly depending on rainfall, inflow and dam operations. The agency continues to monitor the major Luzon reservoirs as weather conditions evolve.
Gates opened at two Benguet dams
PAGASA also reported that one gate at Ambuklao Dam was opened to 0.3 meter, while two gates at Binga Dam were opened to 1 meter on Friday.
The gate operations underscore the importance of closely monitoring reservoir levels even as some dams experience declines, since dam management involves balancing incoming water, storage capacity and downstream safety.
Habagat weakens—but another weather system could bring another turn
The latest dam figures come as PAGASA expects the southwest monsoon to weaken through Saturday, resulting in generally fair weather conditions across much of the country, although localized rain showers and thunderstorms remain possible.
But the weather situation could shift again.
According to PAGASA’s forecast cited by Inquirer, Tropical Storm Saudel, which was outside the Philippine Area of Responsibility, could enter the country between Sunday and Monday and potentially enhance the Habagat once again.
That means the current decline in the number of dams gaining water may not necessarily mark the end of the recent reservoir recovery.
If Saudel strengthens the southwest monsoon, additional rainfall could once again increase inflows into several Luzon watersheds. Conversely, if rainfall remains limited, some reservoirs could resume gradual declines.
Why the dam numbers matter
The condition of the country’s major reservoirs is closely tied to water supply, irrigation, power generation and flood management.
Angat Dam is particularly important because it serves as a major source of water for Metro Manila. Earlier in the year, authorities urged conservation after Angat reached exceptionally low levels.
The recent recovery therefore provides some breathing room—but it does not erase the need for continued monitoring.
The latest figures illustrate how quickly the country’s water situation can change: just two days earlier, seven of the nine monitored dams were reporting increases; by Friday, that number had fallen to four.
For now, PAGASA’s message is clear: the rains have helped replenish several reservoirs, but the recovery remains uneven and weather-dependent.
And with another tropical system potentially influencing the Habagat early next week, the next round of dam readings could tell a very different story.
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