The main function of the two water conglomerates in Metro Manila is to uninterruptedly deliver and provide, as much as possible, potable water to their consumers. Each of the conglomerates draws water primarily from La Mesa Dam and Laguna de Bay. But Metro Manila’s chief water source is Angat Dam located in Barangay San Lorenzo, Norzagaray, Bulacan. This dam supplies ninety-seven percent of Metro Manila’s water needs.
Metro Manila heavily relies on water from Angat, Ipo and La Mesa Dam and likewise, these dams massively rely on rainwater.
Angat Dam, a major dam in the Philippines and part of Angat-Ipo-La Mesa water system, with a normal high level of water of 210 meters above sea level and a minimum operating level of 180 masl, delivers water to the downstream Ipo Dam which the fluvial basin La Mesa Dam gets its water supply. The dam also irrigates approximately 28,000 ha of farmland in Bulacan and Pampanga—both located in the Central Luzon Region.
The Ayala-run MANILA WATER delivers treated water supply to the “East Zone” of Metro Manila such as Makati, Mandaluyong, Marikina, San Andres and Santa Ana in Manila, Pasig, Pateros, San Juan, Taguig, most parts of Quezon City, and municipalities in Rizal like Angono, Antipolo, Baras, Binangonan, Cainta, Cardona, Jalajala, Morong, Pililia, Rodriguez (Montalban), San Mateo, Tanay, Taytay, and Teresa.
On the other hand, the Metro Pacific-run MAYNILAD draws filtered water primarily from Angat Dam and Laguna de Bay and supplies water to the “West Zone” that includes all parts of Manila except San Andres and Santa Ana, some parts of Quezon City (West of San Juan River), West Avenue, EDSA, Congressional and Mindanao Avenues, the northern part of Quezon City starting from the districts of Holy Spirit and Batasan Hills, Makati (West of South Superhighway), Caloocan, Pasay, Parañaque, La Piñas, Muntinlupa, Valenzuela, Navotas and Malabon—all in Metro Manila.
Sometimes low water pressure or total interruption of service occurred when the immediate dam breaches critical low level because of the El Niño phenomenon.
Meanwhile, there were some proposals to expedite the building of China-sponsored Kaliwa Low Dam, a proposed 70-meter dam downstream of the main dam, Laiban Dam, and a water supply tunnel in Tanay, Rizal and in Pagsangahan, General Nakar, Quezon. Its proposed design can handle up to 600 million liters per day (mld) while its 27.7-kilometer raw water conveyance tunnel has a design capacity of 2.4 mld. The ancestral lands to be developed have ever since occupied by the Agta-Dumagat-Remontado ethnic communities in the Sierra Madre mountain range.
In its present structure, Angat Dam can handle and deliver up to 4000 million liters per day (mld) to the two water concessionaires, 2400 mld for Maynilad and 1600 mld for Manila Water, through tunnels, three catchment basins, and six aqueducts into two canals going to Maynilad’s La Mesa Treatment plant and into the “bypass” going to the Manila Water’s treatment plant in Balara, Quezon City.
There were also suggestions for the use of other water sources in augmenting water shortage in Metro Manila like the utilization of Maynilad’s cross-border Plant (50 mld), Manila Water’s new treatment plant (50 mld) in Cardona, Rizal and the revival of old wells (100 mld) which could draw and supplement a total of 200 million liters per day (mld)—sufficient to cushion the impact of water shortage in Metro Manila.