IN THE KNOW: Risks of groundwater extraction

Since 2015, groundwater extraction has been prohibited throughout Metro Manila and certain parts of Bulacan and Cavite provinces, in anticipation of the rise in illegal construction of deep wells during dry spells.

In its latest contingency plan to ease the water shortage in the metropolis, however, the National Water Resources Board (NWRB) has temporarily allowed the Metropolitan Waterworks and Sewerage System to use its existing deep wells to augment water supply for its two concessionaires for the duration of El Niño.

The NWRB, which coordinates and regulates all water-related activities in the country, also plans to temporarily reopen deep wells that were previously closed and sealed subject to the agency’s control and monitoring for critical services.

In its commissioned study in 2004, the agency described the groundwater levels in Metro Manila and adjacent areas as “critical.”

Groundwater extraction, it said, was a major reason floods were taking longer to subside in the northern metropolis.

Severe extraction is also causing land subsidence and seawater intrusion into groundwater, the study said. Subsidence may damage buildings, bridges and highways due to sudden changes in ground elevation.

The NWRBshut down a total of 1,008 illegal or abandoned deep wells from 2008 to 2013.