THE FOLLOWING ARTICLE WAS WRITTEN BY MADELINE DELA PEÑA FOR THE DEPARTMENT OF ENVIRONMENT AND NATURAL RESOURCES
Metro Manila is sinking, and it may be a tragic version of Venice, the famous Italian city famous for its waterways, if the trend of over-extraction of groundwater continues, a geologist from the Marine Science Institute of the University of the Philippines in Diliman has warned.
What’s more, the drying up of aquifers as a result of over-extraction and the consequent sinking or “subsidence’’ of the land is also happening in Bulacan, Pampanga and other places where there is rapid urban development and uncontrolled migration of people, according to the expert, Dr. Fernando Siringan.
“Originally, the Italians never planned to make Venice a city permanently submerged in seawater. It was built above water, on the valley of Italy. But because the Venetians were so much dependent on groundwater, the subsidence was tremendous; the place later became submerged in water. But the Venetians adapted very well, and so they did not destroy the structures of Venice,” Dr. Siringan said.
The geology professor warned that if subsidence in Metro Manila continued, the government will spend billions of pesos to cope with consequent problems like water shortages, flash floods, short supply of fish and other marine products, and even infrastructure damage.
DENR Secretary Lito Atienza has also been very concerned about the degradation of the country’s water resources. “Many of our countrymen take water for granted. They are not aware that many areas in the country are experiencing water shortage because water supply sources are degraded,” Atienza said. One of the sources of freshwater is the aquifers, which must also be brought back to their healthy state.
Former National Water Resources Board (NWRB) Executive Director Ramon Alikpala said that the status of Metro Manila aquifer is critical due to the area’s being below sea level. “There is already saltwater intrusion in some parts of Metro Manila because of over-extraction and the lack of recharging of the aquifer,” Alikpala said.
To avoid an unwanted “Venice-like’’ situation in Metro Manila, concrete actions should be carried out in the short and long-term. One measure that can be immediately done, according to Dr. Siringan, is the strict implementation of laws related to groundwater extraction. Section 42, under Rule II of the Philippine Water Code of 1979, only allows the drilling of wells for domestic purposes and not for commercial uses. It also specifies the spacing, as well as the control devices, needed to operate a domestic pump. He said that a long term strategy would only be to reduce groundwater usage.
This can be taken through the following steps:
• Limit wells to a few operated by municipalities or water utilities;
• Substitute groundwater sources with surface sources;
• Develop small reservoirs and groundwater-replenishing structures to minimize ecological damage; and
• Study and implement rain harvesting such as trapping and storing rainwater from roofs.
The tree-planting program being conducted by the DENR could ease the problem, but the effort should be intensified because of the extent of the crisis. When people could not get water from the water concessionaires, they turn to using wells and pumps to get their water supply. At present, city people no longer use artesian wells but use industrial-type of equipment that quickly pumps up water but dries up the aquifer.
Overextraction happens if the rate of extraction far exceeds the rate of recharge. Over extraction causes the lowering of the water table, reversal of the flow of groundwater, saltwater intrusion, contamination of deeper aquifers, and land subsidence.
An aquifer is the underground layer of water-bearing permeable rock or unconsolidated materials (gravel, sand, silt and clay) from which we extract groundwater.
Saltwater intrusion is now evident in many residential areas of Bulacan and Pampanga, and in Paranaque and Las Pinas in Metro Manila, and also in many coastal areas in the country.
In its nationwide assessment of groundwater level, the NWRB has identified nine areas with critical levels, namely, Metro Manila, Metro Cebu, Angeles City, Baguio City, Bacolod City, Davao City, Zamboanga City, Iloilo City and Cagayan de Oro City. These are areas which are over-populated and have been experiencing rapid urbanization, and which have demands for domestic and industrial water source that are extremely high. These are also areas where the safe yield for underground water resources has been exceeded.
Secretary Atienza asked Metro Manilans to do their share to minimize the use of ground water. “In Metro Manila, we can conserve our use of tap water, so that the reserve water in the La Mesa Dam may reach more people, thus, the need for underground water will be minimized,” he said.
He also said that today is the time to give partnership and collaboration among various government, non-government organizations, funding institutions, and local government units, and even ordinary individuals a chance to address the problem on water resources and water supply sector effectively. “This problem on underground water over-extraction is not only a problem of those areas with no access to potable water. It will eventually involve every one of us because of the attached ecological damage over-extraction would cause”.