Jakarta still sinking, despite groundwater improvements

Indonesia's capital Jakarta is still sinking by 12 centimetres (4.7 inches) per year in northern parts of the city, despite an improvement in groundwater levels blamed for causing land subsidence, an official said on Wednesday.

Extraction of groundwater in Jakarta over the years has caused layers of rock and sediment to slowly pancake on top of each other, causing parts of the city to sink.

Restriction by the local government on extracting water from the Jakarta basin in the past three years had helped improve the ground water levels in the city of more than 10 million people which sources most of its 825 million cubic metres of annual water needs from such extraction, said Rudy Suhendar, head of the geology department at the Energy and Mineral Resources Ministry.

Parts of the Jakarta basin have seen groundwater levels improve to 35 metres below sea level in 2018, compared with 40 metres below sea level five years earlier, he said.

However, the worst of Jakarta's northern shore is still sinking by 12 cm per year, with the added burden of construction and natural movement of soil due to tectonic activities.

The government has announced it intends to move the administrative capital to East Kalimantan province, on Borneo island, due to relieve Jakarta from "a heavy burden" due to overcrowding and pollution.

Jakarta will remain as the country's financial and business centre, however, and the government has pledged to invest $40 billion in modernizing the city, more than the $33 billion expected to be spent on building the new capital in Borneo.

Part of the investment will be extending water pipes across the city to slash reliance on groundwater, according to planning minister Bambang Brodjonegoro.