Stop pumping groundwater to save sinking Jakarta?

Published: 10 June 2015

The advice to legislate against the pumping of groundwater by law to save Jakarta from sinking further was one of the outcomes of an international roundtable discussion on subsidence. If no action is taken North Jakarta may sink up to 3-5 metres below mean sea level in several decades. Increased flood risk and damage to structures caused by land subsidence will result in damage totalling billions of dollars annually.

The roundtable discussion on subsidence was held in Jakarta to discuss a strategy and to identify concrete actions to counter this “hidden” but urgent threat. It was organised by DKI (the Province of Jakarta), PU (Public works), ITB (Technical University Bandung) & Deltares and was supported by JICA (a Japanese aid organisation), and the Dutch and Italian Embassies in Indonesia. The promising outcome was a new strategy, that was presented to and supported by the governor of Jakarta and minister of Public Works and Public Housing:

  • Stop the abstraction of deep groundwater: work towards a “zero policy”
  • The government should take the lead by banning the use of deep groundwater in all government and public buildings
  • Intensify and upgrade subsidence monitoring and research efforts
  • Establish a subsidence task force for the City of Jakarta to focus  on reducing subsidence in Jakarta

Researchers  agree that abstraction of groundwater contributes to subsidence

Jakarta has no time left. Recent flooding events in Jakarta are forcing the city to stop subsidence now. The Round-Table Discussion on subsidence clearly showed that Indonesian scientists have many different views about the main cause of subsidence. It was acknowledged that other factors, such as natural background subsidence and loading by buildings, are also contributory factors. In the end, however, all the researchers agreed that the over-exploitation of groundwater reserves is contributing to subsidence in North Jakarta. A consensus was reached at the round-table meeting that a significant reduction of groundwater abstraction in Jakarta is the only way to mitigate subsidence.

This radical approach must go hand in hand with increased monitoring/research that will also serve to determine whether the proposed measures are effective.

subidence in Jakarta round table meeting

Tour during the round table meeting on subsidence in Jakarta led by Jan Jaap Brinkman, a hydrologist at Deltares.

 

Sharing international experience with mitigation and adaption measures

But Jakarta is not alone. Many deltas and coastal zones around the world are subsiding. The round-table meeting brought together policymakers and scientists from Indonesia, the US, Italy, Japan, the Netherlands and Thailand in the governor’s office in Jakarta to share their experience with mitigation and adaption measures to tackle subsidence elsewhere. The Governor of Jakarta and the Minister of Public Works and Public Housing listened to the conclusions of the discussion. The international experts explained that the active reduction of groundwater extraction was key to curtailing or even stopping subsidence in Tokyo, Venice and Bangkok.

Government should take the lead

Another lesson put forward by the cities involved in the consultations was that government must play an active role in stopping/reducing deep groundwater abstraction. Nearly every large government building in Jakarta relies at present on deep groundwater wells for water supplies, even though many government buildings in Jakarta are physically connected to the piped water supply. The reason is that groundwater is a cheap option because local regulations make groundwater free for government buildings in Jakarta. By introducing clear regulations, including proper piped water budgets and charging for the use of groundwater, the Jakarta Government is planning to take the lead in stopping groundwater abstraction and simultaneously extending the piped water supply. A first step was taken immediately after the round-table meeting when the Jakarta government announced the amendment of Bylaw No. 10/1998 in an effort to limit the utilisation of groundwater and reduce land subsidence.